Manual_2816-2818 Obratiti Paznju

Tettex Test AG, Tettex Instruments Division Bernstrasse 90, P. O. Box, CH–8953 Dietikon Switzerland Phone +41.1.744 74 74, Fax +41.1.744 74 84, www.tettex.com, e-mail: [email protected]

Operation Manual

Fully Automatic Capacitance and Loss Factor tan δ Precision

Measuring Bridge

Type 2816 / Type 2816a

Type 2818 / Type 2818a (valid from firmware version BRC10 onwards)

Release 3

Operation Manual Type 2816 & Type 2818

Nr. 090093-E0-0.M

Last Saved: MT, 11.April 2002 12:34:00

Bridge 2816, 2818 Foreword

Tettex Test AG Tettex Instruments Division

Operation Manual

Page i

Title Fully automatic capacitance and loss factor tan δ measuring instrument Type 2816 / Type 2816a Type 2818 / Type 2818a

Version Release 3

Date 11.April 2002 12:34:00

Author Martin Sigmund, Mark Turner

Layout Martin Sigmund, Mark Turner

Operation manual number 090093-E0-0.M

Number of pages 151

Filename Manual 2816, 2818, English (Edition 3, Office 2000).doc

Foreword Bridge 2816, 2818

Page ii Operation Manual


WARNING! This instrument will be used under high voltage.

Read this operation manual carefully before operating the instrument. The user is responsible for safety during use.

This operation manual is valid for series 2816 and 2818 bridges with firmware version "BRC 10" onwards

Important

Any correspondence regarding this instrument should include the exact type number, instrument serial number and firmware version number. With the exception of the firmware version number, this information can be found on the registration plate on the instrument back panel. The firmware version is briefly displayed on the instrument’s dot matrix display after pressing the REF EXT/INT key. At the time of writing this manual the current firmware version was “BRC 10”.

Note

The design of this instrument will be continuously reviewed and improved where possible. Therefore there may be small discrepancies between the operation manual and the actual instrument. Although all efforts are made to avoid mistakes, no responsibility is accepted by Tettex Instruments Division for the accuracy of this operation manual.

Tettex Instruments Division accepts no responsibility for any damage that may be caused during use of this document. We reserve the right to amend the operation, functionality and design of this instrument without prior notice. If discrepancies are noticed between the on-line help provided by the instrument and the operation manual, then the on-line help should be followed.

All rights reserved. Any use of this manual other than for operation of the instrument requires prior written authorisation from Tettex Instruments Division.

MS, October 2000 Tettex Instruments Division

Bridge 2816, 2818 Foreword


Operation Manual

Page iii

Foreword

Welcome as a new user of the C tan δ measuring bridge Type 2816/2818. Thank you for placing your confidence in our product.

With the purchase of this measuring bridge you have opted for all the advantages that have built a world-wide reputation for Tettex Instruments Division: robustness, performance and quality assured. As a result this instrument provides a solution which achieves the optimal combination of traditional know-how and leading edge technology.

The C tan δ Measuring bridges types 2816 and 2818 were designed with simple operation as a main goal. Parameter entry is menu driven and many useful facilities serve to make the best use of the 12 measurement values.

This operation manual is designed for completeness and easy location of the required information. Customers who already have experience with this kind of equipment will find this document to be of assistance as an extended help. A keyword index at the end of the operation manual greatly eases use.

If you find a mistake or inconsistency in the operation manual then please feel free to contact Customer Support at Tettex Instruments Division with your corrections so that other users may benefit.

Differences between the Type 2816 and Type 2818 measuring bridges

As this manual covers the operation of two versions, the differences between the versions are clarified.

The measurement bridges alone i.e. without the high voltage supply, are operationally identical. As the bridges are intended for different applications, the only difference between them is in the standard capacitor used.

2818 series

When measurements up to 12 kV are to be carried out, use of the Type 2818 is recommended, as this bridge has a built-in 100pF/12kV standard capacitor. For higher test voltages an external standard capacitor can be connected via an additional socket. To complement the 2818, and to form a complete measurement system for up to 12kV (designated Type 2818/5283), Tettex Instruments can supply a specially developed high voltage supply with control unit (12kV/200mA).

2816 series

If measurements are mainly to be carried out with a test voltage of more than 12 kV, then the Type 2816 measuring bridge is recommended, to which a standard capacitor can be connected for voltages up to 1.2 MV. For mobile on-site measurements Tettex can supply a specially developed high voltage supply with control unit (12kV/200mA). The standard capacitor is built into the high voltage supply. The complete test system is designated Type 2816/5284U.

Foreword Bridge 2816, 2818

Page iv Operation Manual


For a quick overview, the various configurations are listed below:

The following measuring bridges are equipped with an internal standard capacitor CNint:

Type 2818 Field version: CNint 100pF/12kV built into the bridge

Type 2818a Laboratory version: CNint 100pF/12kV built into the bridge

Type 2818/5283 Complete measuring system: CNint 100pF/12kV built into the bridge

Type 2816/5284 Complete measuring system: CNint 100pF/12kV built into the control unit

Type 2816/5284U Complete measuring system: CNint 100pF/12kV built into the high voltage supply

The following bridges do not have a built in standard capacitor CNint:

Type 2816 Field version: Measurements only possible with an externally connected standard capacitor CNext

Type 2816a Laboratory version: Measurements only possible with an externally connected standard capacitor CNext

Abbreviations and definitions

Wherever possible the corresponding IEC definitions are used. The following abbreviations and symbols are used in this manual:

CN ..................standard capacitor (Measurement reference)

CX ..................test object (e.g. transformer, generator, motor etc.)

HV .................high voltage

LED ...............Light Emitting Diode

PF..................Power Factor cos ϕ

tan δ ..............Dissipation factor

µP..................Microcomputer

......................Warning: potential danger can occur for operating personnel or third parties through incorrect operation.

......................Attention: advises the user of interesting information and special situations in order to avoid faulty operation or equipment damage.

!

!

Bridge 2816, 2818 Contents


Operation Manual

Page v

Contents

1. Instrument Description 1

1.1. Introduction ................................................................................................................ 1

1.1.1. Hardware............................................................................................................... 1

1.1.2. Firmware ............................................................................................................... 1

1.1.3. Software ................................................................................................................ 2

1.2. Technical Data ............................................................................................................ 3

1.2.1. Conditions for Accuracy Specifications .................................................................. 3

1.2.2. Technical Data, Accuracy Specifications ............................................................... 4

1.2.3. General Data ......................................................................................................... 5

1.2.4. Mechanical Data.................................................................................................... 5

1.3. Mains Supply Connection.......................................................................................... 6

2. Safety 7

2.1. Introduction ................................................................................................................ 7

2.2. Safety Precautions ..................................................................................................... 7

2.3. Warning....................................................................................................................... 8

3. Insulation Measurement Theory 9

3.1. Why is Insulation Tested? ......................................................................................... 9

3.2. What is Loss Factor? ................................................................................................. 9

3.3. What is Dissipation Factor tan δ? ........................................................................... 10

3.4. The Difference between Power Factor cos ϕ and Dissipation Factor tan δ ......... 11

3.5. Apparent Power, Real Power, Reactive Power ...................................................... 12

3.6. Test Instruments ...................................................................................................... 12

3.7. Evaluation of Test Results....................................................................................... 12

3.8. Supplementary Test Methods.................................................................................. 13

Contents Bridge 2816, 2818

Page vi Operation Manual


4. Technical Overview 15

4.1. System Components ................................................................................................15

4.1.1. Standard Capacitor CN .........................................................................................15

4.1.2. High Voltage Supply.............................................................................................15

4.1.3. Measurement Cable.............................................................................................16

4.1.4. Test Object ..........................................................................................................17

4.2. Mains Connection .....................................................................................................17

4.3. Earthing .....................................................................................................................18

4.4. Determining the Maximum Test Voltage and Current through the Test Capacitance at 50 Hz ................................................................................................18

4.4.1. Maximum Test Voltage ........................................................................................18

4.4.2. Minimum Test Voltage .........................................................................................18

4.4.3. Maximum Test Current.........................................................................................18

4.5. Determination of Standard Capacitor Requirements .............................................19

4.6. Conversion Formulae Parallel & Series Equivalent Circuits .................................19

4.6.1. Parallel Equivalent Circuit ....................................................................................20

4.6.2. Series Equivalent Circuit ......................................................................................20

4.7. Functional Description .............................................................................................20

4.7.1. C tan δ Measurement Using the Double Vectorvoltmeter Principle ......................20

4.7.2. The Refined Double Vectorvoltmeter Principle.....................................................21

4.7.3. Interference Suppression .....................................................................................22

4.7.4. Measurement of Inductances ...............................................................................23

4.7.5. Dynamic Average Calculation ..............................................................................24

5. Display and Operation Elements 25

5.1. Instrument Back Panel .............................................................................................25

5.1.1. Mains Power Connection .....................................................................................25

5.1.2. HIGH VOLTAGE Socket on the Type 2818 Measuring Bridge.............................26

5.1.3. HV – GROUND Earth Terminals ..........................................................................27

5.1.4. Measurement Connections and Signal Inputs ......................................................27

5.1.5. Interfaces .............................................................................................................28

5.2. Instrument Front Panel.............................................................................................30

5.2.1. Comments on the Controls...................................................................................30

5.2.2. Display Contrast...................................................................................................30

5.2.3. Grouping of Front Panel Controls.........................................................................30



Operation Manual

Page vii

5.2.4. Display with Measurement Value Keys ................................................................ 31

5.2.5. Operating Elements............................................................................................. 33

5.3. Basic Test Circuit ..................................................................................................... 56

5.4. Typical Procedure .................................................................................................... 57

5.4.1. Typical Measurements on Transformers.............................................................. 57

5.4.2. Use with Additional Components ......................................................................... 58

5.4.3. Choosing the Ideal Standard Capacitor CN .......................................................... 58

5.4.4. Choice of the Ideal Current Comparator for Range Extension ............................. 58

6. The Microprocessor System 59

6.1. General Construction............................................................................................... 59

6.2. Write Protection for the Non-volatile Memory........................................................ 59

6.3. Switch Designations on the Microprocessor Card ................................................ 60

6.4. Non-volatile Memory Power Supply........................................................................ 61

7. Constructing the Test Circuit 63

7.1. Operating Personnel ................................................................................................ 63

7.2. Tips for Setting-up the Test Circuit......................................................................... 63

7.2.1. Location of the Instrument ................................................................................... 63

7.2.2. Connection to System Earth ................................................................................ 63

7.3. Test Setup and Test Modes ..................................................................................... 64

7.3.1. Important points when selecting the correct Test Mode....................................... 64

7.3.2. Important points about the HV Supply ................................................................. 64

7.3.3. Test Mode ........................................................................................................... 65

7.3.4. Description of the individual test modes............................................................... 66

7.3.5. Advantages of the Selectable Test Modes........................................................... 66

7.3.6. Measurements with a Customer Specific Supply with Test Object Current less than 15A....................................................................................................... 67

7.3.7. Maintenance Measurements on Transformers in Accordance with USA Standard ANSI/IEEE C57.12.90-1993 ................................................................. 69

7.4. Measurements with Test Current greater than 15A (with Current Comparator).............................................................................................................. 74

7.4.1. General information on Range Extension ............................................................ 74

7.4.2. Errors caused by External Current Comparators ................................................. 74

7.4.3. Recommendations............................................................................................... 75

7.4.4. Measurements with an External Current Comparator (IX > 15A) .......................... 76


Page viii Operation Manual


7.4.5. Accuracy Considerations when using a Current Comparator ...............................77

8. Getting Started 79

8.1. Preparations Before the Measurement....................................................................79

8.2. Switching on the Instrument....................................................................................79

8.3. Instrument Settings for Measurement.....................................................................80

8.3.1. Settings on the Measuring Bridge Series 2816 ....................................................80

8.3.2. Settings on the Measuring Bridge Series 2818 ....................................................81

8.4. Menu Structure (Brief Operation Guide) .................................................................82

8.4.1. Choice of Standard Capacitor ..............................................................................82

8.4.2. System Reference................................................................................................82

8.4.3. Choice of Connected Printer ................................................................................83

8.4.4. Entering the Measurement Identification ..............................................................83

8.4.5. Optional Functions ...............................................................................................84

8.4.6. Input and Selection of Oil Factor Tables ..............................................................84

8.4.7. Choice of Interference Suppression .....................................................................85

9. Care and Maintenance 87

9.1. Cleaning the Instrument ...........................................................................................87

9.2. Instrument Calibration..............................................................................................87

10. Trouble Shooting 89

11. Instrument Storage 91

12. Packing and Transport 93

12.1. Taking Delivery .........................................................................................................93

12.2. Proof of Despatch .....................................................................................................93

12.3. Scope of Delivery......................................................................................................93

13. Recycling 95

14. Accessories and Options 97

14.1. Options ......................................................................................................................97

14.1.1. Measurement and Interface Cables .....................................................................97



Operation Manual

Page ix

14.1.2. External Standard Capacitor................................................................................ 97

14.1.3. Current Comparators for Range Extension.......................................................... 97

14.1.4. High Voltage Supplies ......................................................................................... 98

14.1.5. Measurement Cells.............................................................................................. 98

14.1.6. Software .............................................................................................................. 98

15. Revisions and Corrections 99

16. Appendix A: Test Circuit Examples 101

16.1. Introduction .............................................................................................................101

16.2. Measurements on a Machine with 2 pole Externally Configurable Winding System .....................................................................................................................102

16.3. Measurement of Short Circuit Impedance in Accordance with IEC 76-5 ..........103

16.3.1. Measurement Procedure ....................................................................................103

16.3.2. Interpretation of Results .....................................................................................103

16.4. C tan δ testing of High Voltage Cables ..................................................................104

16.5. Measurement of High Voltage Bushings ...............................................................105

16.6. Dissipation Factor Measurement on Single-phase Shunt Reactors..................106

16.7. Power Loss Measurements on Three-phase Shunt Reactors with External Terminals .................................................................................................................107

17. Appendix B: Interfaces 109

17.1. Remote Control via IEEE 488 or RS232 Interfaces................................................109

17.2. Introduction .............................................................................................................109

17.3. IEEE 488 Bus Structure...........................................................................................109

17.3.1. Controller:...........................................................................................................110

17.3.2. Talker: ................................................................................................................110

17.3.3. Listener:..............................................................................................................110

17.4. Setting the IEEE Address........................................................................................110

17.5. Concept for Commands and Responses...............................................................111

17.6. Additional Command Set for RS-232 .....................................................................111

17.7. Command Set ..........................................................................................................112

17.8. Error Messages via the Interface ...........................................................................115

17.9. The RS-232 Interfaces .............................................................................................118


Page x Operation Manual


17.9.1. Communications Parameters ............................................................................. 118

17.9.2. Interface and Technical Data ............................................................................. 118

17.10. PRINTER Wiring and Pin-out........................................................................... 119

17.10.1. RS-232 Computer Interface ...................................................................... 120

17.11. IEEE 488 Interface............................................................................................ 121

18. Appendix C: Troubleshooting 123

18.1. Error Messages on the Display.............................................................................. 123

18.2. Hardware Errors during the Measurement............................................................ 124

19. Schematic Diagram 125

20. Instrument Photographs 127

20.1. Views of the Type 2816 Measuring Bridge and Accessories............................... 127

20.2. Views of the Type 2816/5284 Measuring Bridge and Accessories ...................... 129

20.3. Views of the Type 2818 Measuring Bridge and Accessories............................... 131

21. Catalogue of Literature 133

22. Index 135

23. Notes 137

Bridge 2816, 2818 List of Diagrams


Operation Manual

Page xi

List of Diagrams

Figure 1: Disc Capacitor................................................................................................. 10

Figure 2: Parallel equivalent diagram of a lossy capacitance with vector diagram ......... 11

Figure 3: Vector Diagram of Apparent Power, Real power and Reactive Power ............ 12

Figure 4: Alternative series diagram for high voltage supply .......................................... 16

Figure 5: Low conductor resistance measurement cable Rk1, Rk2................................... 17

Figure 6: Parallel equivalent circuit................................................................................. 20

Figure 7: Series equivalent circuit .................................................................................. 20

Figure 8: Schematic diagram of C tan δ measurement double vectorvoltmeter principle 21

Figure 9: Schematic diagram of C tan δ measurement refined double vectorvoltmeter principle .......................................................................................................... 22

Figure 10: Signal processing for interference suppression............................................... 23

Figure 11: Instrument back panel..................................................................................... 25

Figure 12: Mains power connection.................................................................................. 25

Figure 13: HIGH VOLTAGE socket on Type 2818 ........................................................... 26

Figure 14: Earth terminals on the instrument back panel ................................................. 27

Figure 15: Measurement connections CX, CN and signal inputs ....................................... 27

Figure 16: Interfaces for computer and printer ................................................................. 28

Figure 17: Front view of C tan δ measuring bridge type 2816 and 2818........................... 30

Figure 18: Capacitance / Inductance Display ................................................................... 31

Figure 19: Dissipation / Power Factor Display.................................................................. 31

Figure 20: Test Voltage / Current Display ........................................................................ 32

Figure 21: Test Mode display, typical measurement values ............................................. 32

Figure 22: Test Mode keyboard, measurement values / numerical keys .......................... 33

Figure 23 Activating the measurement RUN ................................................................... 35

Figure 24: System parameter keyboard ........................................................................... 35

Figure 25: Test report printout, DIN A4 paper format ....................................................... 55

Figure 26: Basic test circuit for C tan δ measurement ...................................................... 56

Figure 27: Opening the front panel .................................................................................. 60

Figure 28: Microprocessor card switch locations.............................................................. 60

Figure 29: Basic C tan δ measuring system test setup for a transformer with two low voltage windings ............................................................................................. 65

Figure 30: Standard test circuit ........................................................................................ 67

Instrument Description Bridge 2816, 2818

Page xii Operation Manual


Figure 31: Measurable capacitances of an autotransformer with tertiary winding .............70

Figure 32: Measurable capacitances of a transformer with two windings..........................71

Figure 33: Measurable capacitances of a three-phase transformer, Yn – Yn formation....72

Figure 34: Measurable capacitances of a three-phase transformer, Yn-∆ formation.........73

Figure 35: Measurement setup with external current comparator (IX > 15A) .....................76

Figure 36: Displays during the instrument initialization .....................................................80

Figure 37: Pictograms on the transport container .............................................................93

Figure 38: Example of test circuit for a machine with 2 pole externally configurable winding system........................................................................................................... 102

Figure 39: Measurement of short circuit inductances...................................................... 103

Figure 40: Circuit for C tan δ measurement of high voltage cables................................. 104

Figure 41: Circuit for measurement of bushings ............................................................. 105

Figure 42: Block schematic diagram for measurement of single-phase shunt reactors .. 106

Figure 43: Block schematic diagram for measurement of three-phase shunt reactors.... 107

Figure 44: Diagram of the interfaces between three different instruments and the IEEE bus110

Figure 45: Setting the address of the IEEE interface ...................................................... 111

Figure 46: Pin-out of printer socket (male) on the instrument rear panel ........................ 119

Figure 47: RS232 interface wiring measuring bridge - computer .................................... 120

Figure 48: Pin-out of GPIB socket on instrument rear panel........................................... 121

Figure 49: Block schematic diagram of the entire measurement system ........................ 125

Figure 50: Photo of 2816; front view............................................................................... 127

Figure 51: Photo of 2816; rear view................................................................................ 127

Figure 52: Complete 3 part measuring system 2816/5284U consisting of measuring bridge, control unit and high voltage supply 12kV / 200mA............................ 128

Figure 53: Complete 2 part measuring system 2816/5284 consisting of measuring bridge, control unit with high voltage supply 12kV / 200mA ....................................... 129

Figure 54: Photo of 5284 control unit, front view............................................................. 130

Figure 55: Power supply type 5284, Connection part...................................................... 130

Figure 56: Photo of 2818, front view............................................................................... 131

Figure 57: Photo of 2818, rear view................................................................................ 131

Figure 58: Complete 3 part measuring system 2818/5283 consisting of measuring bridge, control unit and high voltage supply 12kV / 200mA ....................................... 132

Bridge 2816, 2818 Instrument Description


Operation Manual

Page 1

1. Instrument Description

1.1. Introduction

The Measuring Bridge Type 2816 / 2818 provides determination of the capacitance and dielectric loss of liquid and solid insulation. Measurements can be carried out on solid insulation such as cables, capacitors, power transformers, generators, motors, bushings etc., and on insulating oil with specially developed Tettex test cells.

Operation is achieved via the scratch proof membrane keyboard on the front panel and offers optimal user friendliness. Operation is simple thanks to the user dialogue system and on-line help.

The system is ideal for high and low voltage measurements at supply frequency. The test setup has been specially developed for efficient use in production and quality control. Thanks to it’s optimum precision, the system is also ideal for laboratory and development use.

1.1.1. Hardware

The bridge section is fully automatically balanced by a microcomputer and the measurement value is displayed on a backlit LCD (liquid crystal display) built into the front panel. The measuring bridge is provided with 2 measurement inputs and 1 earth connection and, as a result, over 14 various parameters can be measured. In addition, the instrument can recognise if an inductive or capacitive test object has been connected and displays this for the user. Noise reduction is provided for field measurements where the measurement results might otherwise be falsified due to magnetic fields.

The combination of the measuring bridge with a high voltage supply, standard capacitor CN and suitable measurement cable provides the user with a complete measurement system.

For maintenance measurements on-site, for which a complete portable measurement system for lower test voltages is required, we recommend the high voltage supply type 5284U for the 2816 and the type 5283 for the 2818. These high voltage supplies have been specially developed for the bridges and consist of a high voltage transformer and control unit. The maximum test voltage is 12kV.

A printer output is provided for generation of measurement data test reports.

1.1.2. Firmware

The firmware is the internal instrument software of the microcomputer for automatic bridge balancing, instrument operation, control of interfaces etc. The instrument is delivered from the factory with the latest firmware version installed in EPROM. This cannot be altered by the user and cannot usually be updated by the operator. At the time of writing this manual the current firmware version is "BRC10". The instrument can display the firmware version.


Page 2 Operation Manual


1.1.3. Software

An optional software package 2816/SWSEQ has been developed for additional user friendliness. This is installed on an IBM compatible computer. The measurement values can be read directly from the RS232C interface.

With this software a measurement routine can be defined. The user simply enters the relevant high voltage values. The measurement values are then automatically read and displayed on the computer screen in curve and tabular format. Subsequent calculations and production of test reports with graphics are then childsplay.



Operation Manual

Page 3

1.2. Technical Data

Unless specified, all technical data refers to both the 2816 and 2818 bridges.

1.2.1. Conditions for Accuracy Specifications

No.

Parameter Unit Reference conditions

Rated range of use

Limit range for storage and transportation

Environmental conditions

1 Ambient Temperature °C 23 ± 2* +5...+40∗ -20...+70

2 Relative Humidity % 45...75* 20...80* 20...80

3 Maximum Dewpoint non-condensing non-condensing non-condensing

4 Air Pressure kPa1 101,3* 70...106* 70...106

5 Magn. Field at Measurement Frequency

µT < 5 < 50

6 Supply Voltage V AC 115 / 230 ±1% 115 / 230 ±10%

7 Supply Voltage Harmonic Distortion

% 3 5

8 Mains Frequency Hz 50 / 60 ±1%* 50 / 60 ±5%

Mechanical Conditions

9 Operating Angle ° horizontal ±30°* horizontal ±90°

10 Vibration negligible* negligible

Test Circuit Conditions

11 Current through CN circuit ICN

A 31µA< ICN <15mA 31µA> ICN <15mA

12 Current through CX circuit ICX

A 31µA< ICX <15A 31µA> ICX <15A

13 Ratio CX/CN 0,5 ... 2000 0,5 ... 2000

14 Measurement Frequency Hz 50 / 60 ±1% 45 ... 65

15 Test Voltage Harmonic Distortion

% ≤ 3 ≤ 5

∗ ...In accordance with IEC 359, Indoor application class 1 1 ...1kPa = kN/m²




1.2.2. Technical Data, Accuracy Specifications

*1 Measuring range depends on CN, Utest, f, Condition: 31µA< ICN <15mA and 31µA< IX <15A *2 Max. input current of the bridge is 15A. With the use of the according HV- Supply the max. output current is 0,2A. *3 The limits of error refers to the rated range of use.

Max. Max.

Parameter Measuring value Resolution Limits of error Remark Display

Test Object Capacitance Cx

50 Hz 60 Hz CN= 100 pF

12kV / 200mA 1kV / 200mA 300V / 200mA

53nF 630nF 2.1µF

44nF 530nF 1.8µF

0.01pF ±0.05% rdg ± 1 dig *1 18 mm LCD

Measuring current extension with supply type 5283 or 5284U up to 4,4A with resonating inductor type 5288 at 12kV / 4.4A at 1kV / 4.4A

1.2µF 14µF

1µF 11.7µF

Inductance Lx *1

with supply type 5286

with supply type 5283 / 84 0,4mH .... 70H

20H ........ 70kH 0.1mH ±0.5% rdg ± 2 dig 18 mm

LCD

Dissipation Factor tanδ 9.99 1·10-4 ±1.0% rdg ±1·10-4 18 mm LCD

Power Factor (PF) cosϕ 1 1·10-4 ±1.0% rdg ±1·10-4 18 mm LCD

Test specimen current IX 15A 0.001mA ±1.0% rdg ± 2 dig *2 18 mm LCD

Test voltage

with CN intern with CN extern

Utest

12kV 1200kV

0.001kV ±1.0% rdg ± 2 dig 4 digits 18 mm LCD

Test frequency f 45...65Hz 00.01Hz ±0.02% rdg 4 digits LCD dot matrix

Apparent power S 999.9kVA 0.001mVA ±1.5% rdg ±1·dig 4 digits LCD dot matrix

Active power P 999.9kW 0.001mW ±1.5% rdg ±1·dig 4 digits LCD dot matrix

Reactive power Q 999.9kVar 0.001mVar ±1.5% rdg ±1·dig 4 digits LCD dot matrix

Quality factor QF 9999 0.001 ±1.0% rdg ±1·dig 4 digits LCD dot matrix

Magnetising current Im 999.9A 0.001mA ±1.5% rdg ±2·dig 4 digits LCD dot matrix

Iron loss current IFe 999.9A 0.001mA ±1.5% rdg ±2·dig 4 digits LCD dot matrix



Operation Manual

Page 5

1.2.3. General Data

Test Object Capacitance CX 0.5 • CN < CX < 20000 • CN

(e.g. with CN=100pF: 50pF ... 1,999µF)

Standard Capacitor CN Built-in 100pF / max. 12kV

External 10pF ... 200nF (see ordering information)

Supply Voltage UNetz: 115VAC or 230 VAC ±10%

Max. Current consumption INetz: Complete system (with HV Supply): 11A at 230VAC 22A at 115VAC

Bridge only: 0.18A at 230VAC 0.36A at 115VAC

Measuring Time for the first measurement 4 s

for subsequent measurements 0.6 s

Interface: Data exchange and remote control via RS232C - interface and IEEE-488 (optional)

Printer Output: For serial printer

Calibration Interval 2 years

Safety Specifications The instrument meets the requirements specified in VDE 0411/part 1a and IEC 348 (Protection Class I)

1.2.4. Mechanical Data

Type Dimensions (W x H x D) Weight

Measuring Bridge (laboratory version) 2818a 500x310x470 mm 20.9x12.8x24.2 in 35kg 77 lb

Measuring bridge (field version) 2818 530x326x615 mm 20.9x12.8x24.2 in 42kg 92.4 lb

HV Transformer 5283/2 530x326x615 mm 20.9x12.8x24.2 in 59kg 130 lb

HV Control Unit 5283/1 530x326 x 615

mm 20.9x12.8x24.2 in 48kg 106 lb

Measuring Bridge (laboratory version) 2816a 500x310x470 mm 19.7x12.2x18.5 in 31kg 68 lb

Measuring Bridge (field version) 2816 570x380 x 560

mm 22.5x14.9x22.0 in 31kg 68 lb

HV Transformer 5284/I 570x380 x 560

mm 22.5x14.9x22.0 in 46kg 101 lb

HV Control Unit 5284/II 570x380 x 560

mm 22.5x14.9x22.0 in 27kg 59 lb

The C tan δ measuring bridge can be built into a 19“ Rack and occupies 6 height units.




1.3. Mains Supply Connection

The mains connection is located on the instrument rear panel. Please read Chapter 2 Safety as well as Chapter 4.1.4 test Object before you connect the mains supply or switch on the instrument.

The mains voltage switch must be set to the correct voltage (115VAC or 230VAC) before connecting the instrument to the mains supply. Otherwise damage may occur to the instrument.

!

Bridge 2816, 2818 Safety


Operation Manual

Page 7

2. Safety

Please read this page before connecting up and switching on the instrument.

When setting up and using the C tan δ measuring bridge with a regulator transformer, high voltage transformer and other high voltage components, certain safety considerations should be observed which are contained in the following standards:

• VDE 0100 (DIN 57100) "Setting up of power equipment up to 1000V"

• VDE 0104 (DIN 57104) "Test systems with voltages above 1kV"

2.1. Introduction

This instrument has been developed, tested and delivered in safe working condition in accordance with the recommendations of IEC 348 „Safety Requirements for Electronic Measuring Apparatus“. The continued safe operation is dependent upon careful reading of this operation manual and observation of the safety advice and warnings therein.

Although the instrument has been developed for indoor use, ambient temperatures within the range +5°C to +40°C will not adversely affect operational safety.

The C tan δ measuring bridge may only be used under dry operating conditions. If the interior of the instrument is subjected to moisture for any length of time then it must not be put straight back into use. Before further use it must be left for a long time in a warm dry room.

The measuring bridge described in this operation manual may only be operated by suitably qualified personnel. Setup, adjustment, service and repair of the uncased instrument are only to be carried out by professionally qualified personnel.

2.2. Safety Precautions

Ensure that an earth cable is securely connected to the earth screw terminal (on instrument back panel) before any other cable connections are made.

PLEASE BE AWARE, THAT YOU ARE RESPONSIBLE FOR SAFETY!

During the measurement the test object CX and the standard capacitor CN, which are connected to the circuit, are under high voltage. All personnel involved must observe all safety precautions to avoid contact with the live voltage components. The personnel involved in the measurement must be situated at an adequate distance from all live voltage components in the test circuit. All personnel not involved in the measurement must be prevented from accessing the test area by the use of suitable safety barriers, enclosures and clear warning signs. The test area may only be entered when the test circuit is without voltage and all components of the high voltage circuit are visibly earthed.

!

Safety Bridge 2816, 2818



The high voltage test equipment and the test object should preferably be located in an enclosed room. All test equipment that is provided with a high voltage source must be equipped with appropriate safety circuits.

Never insert the mains plug into a mains socket without a protective earth contact. The earth protection must not be compromised e.g. by use of an extension cable without an earth connection. The use of an unearthed connection cable would interrupt the earth protection for the entire measurement system and the operator, and is therefore life threatening.

To ensure correct operation of the earth protection, the mains lead must be securely inserted in the socket, before any measurement or control cables are connected.

2.3. Warning

Any interruption of the earth path inside or outside the instrument, or a break in the connection to the earth terminal could be dangerous! A deliberate interruption of the protective earth path is strictly forbidden!

Setup, service and repair of the open instrument, when voltage is applied, is to be avoided if at all possible. If access is absolutely require under these conditions, then the work must only be carried out by suitably qualified personnel who are fully aware of the dangers present.

When replacing defective fuses it must be ensured that the new fuses are of exactly the correct type and current rating. The use of temporary home-made fuses and short-circuiting of fuse holders is forbidden.

In case of suspected damage, the instrument should always be removed from use and secured against further switching on.

There is likelihood of damage to the electrical protection if, for example:

• visible damage has occurred (transportation, mishandling, ...)

• the planned measurements cannot be performed

• the equipment has been stored for a long time in unsuitable conditions.

!

Bridge 2816, 2818 Insulation Measurement Theory


Operation Manual

Page 9

3. Insulation Measurement Theory

3.1. Why is Insulation Tested?

All transformers, high voltage switchgear, motors and electrical equipment accessories have a high voltage life expectancy. From the first day of use the equipment is subject to thermal and mechanical stresses, foreign particle ingress and variations in temperature and humidity. All of these influences raise the working temperature of the equipment when switched on. This heating accelerates chemical reactions in the electrical insulation, which result in a degradation of the dielectric characteristics. This process has an avalanche character i.e. the changing electrical characteristics of the insulation increase the loss factor and produce heating which further degrades the insulation. If the loss factor of the insulation is periodically monitored and recorded, it is possible to predict and/or avoid catastrophic failure of the electrical equipment.

At the beginning of the public electricity supply industry, methods and processes were sought to avoid unexpected losses caused by equipment defects. One method that provided repeatable data and offered simple on-site measurement was the measurement of capacitance and loss factor ( power factor) of the equipment insulation.

In cases where loss factor tests were regularly carried out, and the relevant test results compared with earlier results, the deterioration of the insulation was noted and necessary preventative measures were carried out. Based on this groundwork, a series of test procedures were developed and described in various IEEE, ANSI and IEC documents and standards to specify the insulation quality for various types of electrical equipment. These standards subsequently served as the basis for development of the Tettex measuring bridges and the introduction of associated software.

In order to define acceptable loss factor values, a „data record service“ was developed based upon statistical data that related to specific equipment types and models. Standard measurements of capacitance and loss factor of the electrical insulating medium were carried out to ensure that the data was comparable. The loss factor was calculated and the results were corrected by energy comparison to a value for a test voltage of 10kV. Some test results were further multiplied by a temperature correction factor to produce 20°C compatible values. Any results that are now acquired at different test voltages and temperatures are recalculated for 10kV and / or 20°C and then recorded and compared. In this way the degradation of the insulation characteristics over a specified period of time can be determined. With the test result history - based on a specific measurement instrument - an experienced engineer is able to take the necessary maintenance actions based upon changes in the value of loss factor.

3.2. What is Loss Factor?

Loss factor is the total energy that will be used by the equipment during normal service. In particular, the insulation loss factor is any energy that is taken by the flow of current through the resistive component of the insulation. The earth path varies according to the type of electrical equipment. For example, switchgear will probably develop tracking to earth at right angles to the floor connections. In transformers paths can develop in the insulation resistance between

Insulation Measurement Theory Bridge 2816, 2818



the windings or between the windings and housing (tank). In all cases the result is a loss factor in the form of heating.

Note: in this text loss factor is referred to, in contrast with total loss factor. Total loss factor is normally used to describe the total losses of the transformer under load and should not be confused with the energy that is lost due to degradation of the insulation.

3.3. What is Dissipation Factor tan δ?

To specify the insulation loss factor, the test object must be considered in the test arrangement as a capacitor. Consider all test objects e.g. transformers, bushings, busbars, generators, motors, high voltage switchgear etc. are constructed from metal and insulation, and therefore possess associated capacitive properties. Every test object consists of various capacitances together with the insulation and the internal capacitance to earth. Figure 1 shows the components that comprise a capacitance and the diagram for a simple disc capacitor.

Figure 1: Disc Capacitor

In an ideal capacitor the resistance of the insulation material (dielectric) is infinitely large. That means that, when an AC voltage is applied, the current leads the voltage by exactly 90° as it flows as pure current.

After further consideration it must be realized that every insulation material contains single free electrons that show little loss under DC conditions with P= U2/R. Under AC a behavior called dielectric hysterisis loss occurs which is analogous to hysterisis loss in iron.

dA

ε

CA

d=

⋅ε

Key: A....... electrode face d ....... distance between the electrodes C....... capacitance ε0 ...... dielectric constant of air (ε0=8,8542•10-12 F/m) εr ....... relative dielectric constant dependent upon material ε........ ε = ε0 • εr, dielectric constant



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Page 11

As losses therefore occur in every insulation material, an equivalent diagram of a real capacitance can be constructed as follows:

Figure 2: Parallel equivalent diagram of a lossy capacitance with vector diagram

Key to Figure 2:

UTest...... applied test voltage

IC .......... current through capacitance

IR .......... current through resistance (insulating material)

C .......... ideal capacitance

R .......... ideal resistance

Because P = Q • tan δ, the losses which are proportional to tan δ, will usually be given as a value of tan δ to express the quality of an insulation material. Therefore the angle δ is described as loss angle and tan δ as loss factor.

3.4. The Difference between Power Factor cos ϕ and Dissipation Factor tan δ

While Dissipation Factor tan δ is used in Europe to describe dielectric losses, the calculation used in the United States is „Power Factor“ cos ϕ.

The statistical data that have been collected in North America have been calculated using the loss factor cos ϕ („Power Factor“) to specify the power losses in the insulation. Because the angles are complimentary it is unimportant whether tan δ or cos ϕ is used as with very small values the difference is negligible.

I

II C R

UTest

I R

I C I

UTest

δ

ϕRC

Loss factor (Dissipation Factor)

tanδω

= = = =⋅ ⋅

PQ

II

XR C R

R

C

R

C

C 1

Power Factor

PFII

PS

R R

C= = = =

+cos

tan

tanϕ

δ

δ1 2




3.5. Apparent Power, Real Power, Reactive Power

The relationship between the various types of power is clarified in the following equations.

Apparent Power: S = U·I [VA]

Real Power: P = U·I cos ϕ [W]

Reactive Power: Q = U·I sin ϕ [var]

Figure 3:

Because most test objects are not a pure resistance and therefore have a phase angle ϕ between the test voltage and current, this phase shift must also be taken into consideration in the power calculation.

3.6. Test Instruments

There are three basic kinds of capacitance, tan δ and Power Factor test instruments in use.

1. Although the high accuracy Schering Bridge must be balanced manually and the balance observed on a null indicator, it has been widely sold and used for decades up until this day. The capacitance and dissipation factor can be calculated by reading the position of the balance elements.

2. The automatically balanced C tan δ measuring bridge performs measurement by the differential transformer method. The automatic balancing makes operation very easy.

3. The vector voltmeter method is essentially a modification of the differential transformer method.

All three methods are in current use for accurate and repeatable measurements of C tan δ on various test objects. The differences basically lie in the resolution and accuracy. Different instruments are generally developed specially for field or laboratory measurement.

Field instruments are specially constructed for rugged field requirements and are equipped with a high voltage source with a maximum test voltage of 10kV. In addition, such instruments are provided with a wealth of special features such as conversion tables to correct to 20°C and noise suppression for accurate measurements in electromagnetic fields.

Laboratory instruments have been constructed for indoor use where high accuracy specifications are required. These test systems are built in a modular construction for higher test voltages. The systems may be used for daily routine testing, for high precision long duration tests or for acceptance tests.

3.7. Evaluation of Test Results

The absolute value of the dissipation factor varies between different test objects. Statistical data has been collected over the years and the manufacturer can advise typical dissipation factor

Q

P

ϕ

S



Operation Manual

Page 13

values based upon the test object type, model and maintenance interval. A better solution is to establish the previous test history for every test object in order to establish test curve trends.

On some apparatus e.g. bushings the dissipation factor is sometimes given on the identification plate. There are several guidelines that can be used to establish if a test object has an insulation problem. For example:

• High voltage generators and motor windings have less than 3%

• Power transformers have less than 2%

• instrument transformers have less than 5%

• High voltage bushings have less than 1.5%

These guidelines can differ from the actual values and acceptable limits depending upon the manufacturer, model, maintenance interval, type of maintenance carried out and ambient conditions. It must be mentioned that numerous statistical values have been gathered in mW instead of raw data (PF or tan δ). The mW losses are the real power losses in the insulation calculated at either 2.5kV or 10kV.

3.8. Supplementary Test Methods

As of today there exists no other test method that can replace the currently used C tan δ test. Nevertheless, several measurement methods exist which compliment dissipation factor measurement and assist in localization of defects in the test object.

Partial Discharge Measurement is unprotected against external electromagnetic disturbances and on-site measurement presents quite a lot of problems.

Oil Analysis Measurements provide useful information about the insulating oil in transformers and oil-paper insulation systems.

Megger Test results are not comparable with earlier test results and are influenced by changes in ambient conditions.

The Recovery Voltage Meter RVM provides information about the aging condition of the oil-paper insulation. This method cannot currently be used for testing synthetic insulation.




Bridge 2816, 2818 Technical Overview


Operation Manual

Page 15

4. Technical Overview

4.1. System Components

As the Measuring Bridge requires certain accessories to form a complete system, the additional components are briefly explained below. The basic setup for the measuring bridge consists of the standard capacitor, the high voltage supply and the actual test object. Of course, in addition to the accessories and the test object, a measurement cable is also required.

4.1.1. Standard Capacitor CN

The standard capacitor The TCN is the standard to which the whole measurement refers and with which the test object is compared. Therefore the demands placed upon this test standard are high e.g. tan δ less than 1·10-5, good long term stability and exact capacitance value. The quality of the standard capacitor is therefore an important integral part for the accuracy of the complete test system. It is recommended to use a Haefely product for this test standard. Haefely has a large selection of standard capacitors to suit various test objects and high voltage supplies.

4.1.2. High Voltage Supply

The quality of the high voltage supply is also important for the measurement accuracy of the complete test system. In order to be able to perform measurements on earthed test objects it is useful to have a double screened supply. Without this double screening the influence of stray capacitance is increased.

The output voltage should be distortion free i.e. the purity of the wave shape is important. If the supply voltage contains harmonics then the capacitive load of the test object (and the standard capacitor) will also be stressed with these harmonics. The result is the multiple of the number of the power supply harmonic (e.g. 5% of third harmonic in the power supply produces 15% in the measuring bridge).

To prevent undesired harmonics reaching the test object it is advantageous to use a resonant circuit arrangement (see Figure 4).

For measurement at low voltages it is an advantage to connect the smoothing inductor L to the transformer.

Of course a parallel resonant arrangement can also be used. In this case the smoothing inductor L must be connected parallel to the input connectors of the transformer. It is also possible to make the parallel connection on the secondary side of the transformer.

Technical Overview Bridge 2816, 2818



S L Z1 Z2

MCX CN

∼

Figure 4: Alternative series diagram for high voltage supply

Key:

Z1, Z2.....stray inductance of the transformer

M ............no-load inductance of the transformer

S.............stray inductance of the current source

L .............smoothing inductor

CX ........... test object

CN ...........standard capacitor For on-site maintenance, when a portable complete test system is required for lower voltages, we recommend the high voltage supply type 5284U. This high voltage supply was specially developed for this measuring bridge and consists of the high voltage supply type 5284/2U with a built-in standard capacitor (100pF/12kV). The maximum test voltage is 12kV. With the C tan δ measuring bridge and this special high voltage supply the user is equipped with a valuable test system.

4.1.3. Measurement Cable

It should be ensured that the conductor resistance of the measurement cable is as low as possible. The conductor resistance falsifies the tan δ measurement if the capacitance of the test object is very large.

To avoid errors in the measurement of tan δ, which can arise from test circuit current, particular attention must be given to the conductor resistance of the connecting cable. When measuring a test capacitance of 500µF at 50Hz with a series resistance of 0.01Ω, caused by the measurement cable, an additional tan δ value of 0.00157 is produced. With such large capacitances the conductor resistance Rk2 of the connection between the test object and bridge must be kept as low as possible by use of a short measurement cable with a large cross section. The influence of the cable resistance Rk1, between the supply and the test object, can be eliminated by connecting the high voltage terminal of the standard capacitor directly to the test object (see Figure 5).



Operation Manual

Page 17

Figure 5: Low conductor resistance measurement cable Rk1, Rk2

4.1.4. Test Object

Test objects, shown as Cx, (see Figure 2 in Chapter 4.1.3 Measurement Cable)are components or insulation materials of which the capacitance or the dielectric losses are to be measured. The insulation material may be solid or liquid (e.g. insulating oil). Measurements can be carried out on power transformers, measurement transformers, bushings, switchgear, surge arrestors, capacitors, motors, generators, cables etc.

For measurements with insulating materials in liquid or solid form, specially developed test cells are recommended which can be ordered as optional accessories from Tettex Instruments Division. The relative permitivity (dielectric constant) ε and dissipation factor tan δ can then be determined.

4.2. Mains Connection

The power cable provided must be used for connection to the mains supply. The C tan δ measuring bridge type 2816 is equipped with a current supply which can provide various output voltages. This internal supply does not automatically adjust to the supply voltage. Therefore the supply voltage must be switched to either 115VAC or 230VAC. The instrument is factory set to the voltage specified by the customer.

Warning: The C tan δ measuring bridge can be used with 115VAC or 230VAC. It is essential that the voltage setting of the instrument is checked before connecting to the mains supply. If the mains voltage differs from that shown on the mains socket of the instrument, then the bridge and the high voltage supply must

be set to the required mains voltage.

∼vCX CN

G

P

Type 2816 or 2818

N1 N2

NI

CNCX

UTest

E

Rk2

Rk1

tan δ X

µ

!




4.3. Earthing

Special attention should be paid to the earthing connections as safety and measurement accuracy are dependent upon them. It is always recommended to carefully inspect the earthing connections for every test circuit.

Removal of earthing connections, either on the power cable or at the earth connection of the instrument, results in the instrument floating above earth potential. This is extremely dangerous when high voltage measurements are performed on test objects.

4.4. Determining the Maximum Test Voltage and Current through the Test Capacitance at 50 Hz

4.4.1. Maximum Test Voltage

If nothing is specified in the appropriate standards, then we recommend measurement at service voltage as the losses in normal use are of interest. Higher voltages run the risk of flashovers.

If you are uncertain, we recommend that you follow the relevant standards. For specialized questions please contact the Customer Support Department at Tettex Instruments Division.

The maximum test voltage that must not be exceeded, in order to avoid damage to the instrument, can be calculated as follows:

UI

f CTest

CN

Nmax

max=

⋅ ⋅ ⋅2 π ICN max ≤ 15 mA

4.4.2. Minimum Test Voltage

The instrument requires a minimal test voltage in order to be able to perform a useful measurement. As the test voltage is measured by the current ICN through the standard capacitor, the minimum voltage at which full measurement precision can be obtained can be calculated as follows:

UI

f CTest

CN

Nmin

min=

⋅ ⋅ ⋅2 π ICN min ≤ 31 µA

The minimum test voltage at which the instrument no longer produces a test result is actually considerably lower.

4.4.3. Maximum Test Current

The maximum test current increase with the test capacitance Cx and the test voltage UTest (with normal loss insulation material where the tan δ is relatively small). This is clear from the following formula:

I U f CX Test x= ⋅ ⋅ ⋅2π

Example: UTest = 10′000 V

!



Operation Manual

Page 19

CX= 1 µF f= 50Hz tan δ < 10-2 Test Instrument Type 2816 (IX< 15A) Calculated maximum test current:

IX = 10′000·2π·f·1·10-6 = 3.14 A

This means that a measurement on a test object capacitance of 1 µF at 10kV / 50 Hz amounts to a test current of 3.14A. This measurement can be performed without hesitation for test objects with normal loss insulation having a small dissipation factor tan δ.

The above calculation is actually valid for purely capacitive test objects (tan δ= 0). It can also be used as an approximation for lossy test objects, as long as the tan δ is not larger than 0.01.

The maximum test current IX must not be larger than 15A. If this were to be exceeded then the measuring bridge could be damaged (the in-built protection will trigger). When measuring very large test capacitances, where the measurement current is greater than 15A, an external high precision current comparator must be employed to extend the current range. Tettex Instruments has specially developed a range of high precision current comparators that have a transfer error of just a few ppm (parts per million) and an error angle of hundredths of a minute.

4.5. Determination of Standard Capacitor Requirements

Before the standard capacitor can be determined, the following must be known: • Which capacitance values are to be measured? ð Minimum value <CX < Maximum value • How large is the maximum test voltage? • What is the test voltage frequency? If the above limiting values are known then the standard capacitor can be determined in conjunction with the requirements listed in the data sheet. (see Chapter 1.2 Technical Data). These requirements are:

⇒ Current through standard capacitor ICN 31µA ≥ ICN ≤ 15mA

⇒ Ratio between test capacitance and standard capacitor CC

x

N≥ 1

⇒ Of course, the maximum test voltage must not be larger than the nominal voltage of the standard capacitor. UTest ≤ UCN

If it is not yet known exactly which capacitance is to be measured, we recommend use of a standard capacitor with a capacitance value of 100pF. Using this standard capacitor, test objects can be measured within the range ca. 50pF to 2 µF.

4.6. Conversion Formulae Parallel & Series Equivalent Circuits

See also Chapter 5.2.5.3.6.5 OPT 5; Conversion between series / parallel equivalent circuits - C serie




4.6.1. Parallel Equivalent Circuit

The Type 2816 measuring bridge measures the parallel equivalent circuit Cp-Rp of the test object Cx.

RpCp

=⋅ ⋅

1ω δtan * *

*......measured value

Figure 6: Parallel equivalent circuit

4.6.2. Series Equivalent Circuit

The following conversion formula is valid for the series equivalent circuit Cs-Rs:

Cs Cp= ⋅ +* ( tan *)1 2 δ

Rs Rp= ⋅+tan *

tan *

2

21δ

δ

*......measured value

Figure 7: Series equivalent circuit

4.7. Functional Description

4.7.1. C tan δ Measurement Using the Double Vectorvoltmeter Principle

The double vectorvoltmeter method relies upon measurement of the current IN through the known reference capacitor CN and measurement of the current IX through the unknown test object CX. Both currents are galvanically separated and transferred by an instrument transformer, and finally converted into voltages. Both voltages UX and UN are then separated into real and imaginary components, which facilitates the calculation of CX and tan δ.

Rp

Cp

Cs Rs



Operation Manual

Page 21

4.7.1.1. Schematic diagram of C tan δ measurement double vectorvoltmeter principle

Figure 8: Schematic diagram of C tan δ measurement double vectorvoltmeter principle

As this principle only functions when ICX and IRX are of a similar order of magnitude, a „trick“ must be used in order to reach the required accuracy. Further, it should be observed that the input stage of such a system is a differentiating circuit and, as a result, all kinds of harmonics can have a strong influence on the measurement signal. Additionally, only relatively lossy test objects with losses in the region of 10% and upwards can be measured.

4.7.2. The Refined Double Vectorvoltmeter Principle

The following „trick“ is applied in order to be able to measure test objects with small losses. (see Figure 9):

The purely capacitive signal from channel N- is taken, the polarity inverted and applied to channel X- such that the ICX- component is compensated for as completely as possible. The very small IRx- component remains, which is then amplified and can be measured with good resolution. In addition, very selective filters are inserted in both the N and X channels such that the 50Hz (60Hz) component is eliminated from the „target“ measurement signal. Further, both channels are provided with programmable amplifiers. For completeness, the N- channel signal is rectified to obtain a signal that is proportional to the test voltage UTest.

Key:

PSG .....Phase Selective Rectifier µP ........Microprocessor Re ........Real component Im......... Imaginary component XRe........Real component of test object XIm ........ Imaginary component of test object NRe .......Real component of standard capacitor NIm ........ Imaginary component of standard

capacitor CX.........Test object (ideal capacitance) CN.........Standard capacitor (with tan δ < 1 • 10-5) RX......... test object losses UTest ......Test voltage

~

u

C N

IU

PSG

IU

PSG

C X U TestR X

INICx

IRx

IX

UX IX~ UN IN~

X- Channel N- Channel

NRe N ImX Re X Im

NRe

N Im

X Re

X Im , tan δC NµP




4.7.2.1. Schematic diagram of C tan δ measurement refined double vectorvoltmeter principle

Figure 9: Schematic diagram of C tan δ measurement refined double vectorvoltmeter principle

With the measurement system shown in Figure 9 measurement values of CX, tan δ, UTest, cos ϕ, SX, PX, QX, and IX can be determined and displayed

4.7.3. Interference Suppression

Interference Suppression is particularly effective in surroundings with magnetic and electrical alternating fields.

The presence of such disturbances can be verified by switching the polarity of the high voltage. If, as a result, the displayed measurement varies greatly then this can be attributed to disturbances and a measurement with interference suppression is then recommended.

C N~

u

IU

PSG

C XR X U Test

IN

ICxIRx

IX

X- Channel

IU

PSG

UN IN~

N- Channel

NRe N ImX Re X Im

IU

X~~~ ~~~

ACDC

UN Utest~

Filter

Gain programmableamplifier

Phase selectiverectifier



Operation Manual

Page 23

Such situations are often encountered during maintenance measurements i.e. measurements to check the condition of equipment currently in use. Such equipment is mostly found in electrical utility substations, where high voltages and currents are present. The associated alternating fields can induce disturbance voltages in the test circuit. Such influences can cause strong instability in the measurement value and can even altogether prevent a meaningful measurement. The induced interference voltages must be compensated for.

4.7.3.1. Schematic diagram interference suppression; signal processing

Figure 10: Signal processing for interference suppression

Signal processing for interference suppression requires the following modules: a signal from the network voltage UTestAC, an amplifier stage that can be set to +1 or –1 and a 90° phase shifter. The amplifier stage can generate signals of 0° and 180° phase, as well as -90° and -270°. The two signals UKomp RE and UKomp IM can be weighted with potentiometers P1 and P2 and a further stage adds the two signals together.

With the principle shown in Figure 10, a signal can be generated with amplitude 0...UTestAC and phase 0° ... -360° i.e. a compensating vector can be produced that can lie in all 4 quadrants. Using this compensations vector, any interference voltage (synchronous to the supply) can be nulled.

4.7.4. Measurement of Inductances

So far only measurement of capacitances has been discussed. However, this system also enables the measurement of inductances.

inductances produce a 180° phase shifted voltage in comparison with capacitances, which means that the measurement signal vector has the opposite polarity. For this, there is another stage built in, which subtracts the inductive component from the measurement signal before the capacitive component is compensated away (see Figure 47: Block schematic diagram of the complete measurement system). In this way, an inductance LX, equivalent resistance and quality factor QL can be determined using the same method as for capacitance measurement,.

As a kind of by-product, the magnetizing current of LX and the losses as apparent, real and reactive power can be calculated from the measured values of LX, QL, fTest and Utest, and displayed.

~UTest

±1

±1phaseconverter

90°

P1

P2

+

+

UKomp

UKomp IM

UKomp RE




4.7.5. Dynamic Average Calculation

If measurements are desired at low test voltages (<1kV with CN= 100pF), the signal to noise ratio will be unfavorable and the measurement value will be unstable. A good result can be obtained by calculating the mean value:

mn

mii

n

= ⋅=∑

11

Further investigation using the method of smallest error quadrant gives

Sn

Sm ii

n2 2

1

11

=−

⋅=∑ Si ...error of a single measurement

the mean quadratic deviation or variance, a measure that indicates how the measurements vary from the mean value.

The standard deviation can be calculated from the variance:

SSn

m =

The standard error of the mean value Sm from n measurements is also the same as the standard error of a single measurement divided by n .

From the above reasoning it can be seen that a mean calculation using relatively few measurement values is sufficient to increase the measurement accuracy, even under difficult conditions.

1

5 10 15 20n

Sm

S

n

Bridge 2816, 2818 Display and Operation Elements


Operation Manual

Page 25

5. Display and Operation Elements

5.1. Instrument Back Panel

Figure 11: Instrument back panel

5.1.1. Mains Power Connection

Figure 12: Mains power connection

INPUTA

INPUTB

INPUTC EXTERNN

v

HV - GROUND

HIGH VOLTAGE

MAINS

CONTROL

PRINTER

INTERFACEIEEE 488Tettex Instruments

FUSE

CURRENT

FREQUENCY

VOLTAGE

SERIAL NO.

TYPE

VAC

Hz

A

A

MAINS

Mains voltage selector 115/230V

Mains Safety fuseholder

Socket for connection of the supplied mains cable

Display and Operation Elements Bridge 2816, 2818



The socket for the mains cable is located on the instrument back panel. For safety reasons only the supplied power cable should be used with the instrument.

Above the mains socket is a slide switch for selection of the mains voltage (115VAC or 230VAC).

!

Before the instrument is connected to the mains, it is vital that the mains selector switch is set to the correct supply voltage (115VAC or 230VAC).

If your equipment comprises a complete measurement system consisting of measuring bridge and specially developed 12kV high voltage supply, then the measuring bridge can be directly connected to the mains cable of the control unit. If the mains switch of the measuring bridge is left switched on, then the complete test system can be switched on or off by using the central mains switch of the control unit.

5.1.1.1. Mains fuses On the mains socket panel, above the actual mains socket, there is located a fuseholder which contains a slow-blow fuse (5x20 mm). The fuseholder also contains a replacement fuse of equal rating. The instrument is delivered with the correct mains supply voltage already selected. Depending upon the mains voltage, the following fuses are installed:

115 VAC 2A slow-blow

230 VAC 1A slow-blow

!

The instrument must be disconnected from all voltage sources if a fuse has to be replaced or the instrument has to be opened.

When replacing the mains fuse always use a replacement fuse with the same specifications and current rating. Otherwise the instrument could be damaged.

5.1.2. HIGH VOLTAGE Socket on the Type 2818 Measuring Bridge

The input socket for high voltage is only found on the Type 2818 and 2818a measuring bridges, as only these instruments have a built-in standard capacitor to which the high voltage must be connected.

Measuring bridges Type 2816 and 2816a are not equipped with this high voltage input socket, as they do not have a built-in standard capacitor.

The plug and socket connector has been developed specially for high voltage by Tettex Instruments and is designed for a maximum voltage of 12kV.

Figure 13: HIGH VOLTAGE socket on Type 2818

HIGH VOLTAGE



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Page 27

5.1.3. HV – GROUND Earth Terminals

Figure 14: Earth terminals on the instrument back panel

Key: HV- Ground... Earth terminal for the high voltage supply v.................... low voltage point of the high voltage supply i.e. reference point of the test circuit

Reliable and clean earth terminals are important for safe and accurate measurements. A solid earth connection between the test area and the earth terminal on the instrument back panel is highly recommended.

When using this instrument with the specially developed high voltage supply it is essential that the HV ground connection is never connected to mains earth, otherwise the safety circuit will be bypassed (see high voltage supply operation manual).

5.1.4. Measurement Connections and Signal Inputs

Figure 15: Measurement connections CX, CN and signal inputs

Key: INPUT A............... measurement channel A input INPUT B............... measurement channel A input INPUT CN EXTERN ... standard capacitor CN input Special single pole, single shielded measurement cables fitted with "Lemma“ plugs are provided for measurement. These plugs (Tettex Order Nr. 010689-00-0.7) are protected against unintentional disconnection and plug into the appropriate sockets (INPUT A, INPUT B, INPUT CN EXTERN) on the instrument back panel.

The v connector is the low voltage point of the high voltage supply and must never be identical to the system earth. Connection to the v socket can be made with a 4mm banana plug or by using the screw terminal.

v

HV - GROUND

!

INPUTA

INPUTB

INPUTC EXTERNN

v

HV - Ground




System earth connection can be made using the screw terminal or the 4mm socket. If system earth is to be connected to the low voltage point of the high voltage supply (v connector), then this can be achieved using the link supplied.

When using this instrument with the specially developed high voltage supply it is essential that the HV ground connection is never connected to mains earth, otherwise the safety circuit will be bypassed (see high voltage supply operation manual).

5.1.5. Interfaces

Figure 16: Interfaces for computer and printer

All connections for computer or printer are located on the rear panel of the instrument.

The following interfaces are provided:

INTERFACE IEEE 488 Interface for remote control of the measuring bridge. Although Interface IEEE 488 is printed on the panel, the standard built-in interface is RS 232. An IEEE interface can also be built in as an option (see chapter 5.1.5.1).

PRINTER Interface for connection of an external serial printer for test reports.

CONTROL Interface for connection to the associated high voltage supply control unit. This is only needed if the measuring bridge is being used with the matching high voltage supply. Measuring bridge type 2816 è high voltage supply type 5284U Measuring bridge type 2818 è high voltage supply type 5283

5.1.5.1. RS232 / IEEE 488 interfaces for remote control The instrument can be completely remote controlled via the RS232 or optionally available IEEE interfaces. Additionally, all displayed measurement values can be read. The instrument cannot be fitted with both interfaces, either RS232C or IEEE 488.

!

CONTROL

PRINTER

INTERFACEIEEE 488



Operation Manual

Page 29

!

Attention:

Connection is made via the INTERFACE IEEE 488 socket, even if the built-in interface is RS 232C. If the RS 232C interface is fitted then a special adapter cable is supplied (Nr. 020219-00 IEEE 488 / RS232C). This facilitates connection of the RS 232C cable to the INTERFACE IEEE 488.

Remote control capability can be fully exploited by our optional RS 232C software that facilitates easy test solutions as well proof of testing in accordance with relevant standards. For customers who wish to write their own software the complete command set is provided in Chapter 17 Appendix B Interfaces.

Note: Ensure that a screened cable is used for data transfer so that disturbances do not influence the data. Such disturbances, caused by e.g. impulse testing or flashovers, can result in faulty operation or in worst cases can damage the computer.

5.1.5.2. PRINTER interface The PRINTER interface is available for producing test data reports on an external printer. This PRINTER interface is an RS 232C interface. Production of a test value printout is achieved by pressing the relevant key on the front panel of the measuring bridge (see Chapter 5.2.5.3.8 Printing measurement values PRINT). Every press of the PRINT key sends an ASCII character set which will be printed out as lines.

5.1.5.3. High voltage supply interface CONTROL Interface for connection to the associated high voltage supply control unit. This is only needed if the measuring bridge is being used with the matching high voltage supply.

Measuring bridge type 2816 è high voltage supply type 5284U

Measuring bridge type 2818 è high voltage supply type 5283




5.2. Instrument Front Panel

Figure 17: Front view of C tan δ measuring bridge type 2816 and 2818

5.2.1. Comments on the Controls

The controls (keys) of the instrument are not switches in the normal sense, but rather piezo-crystals that produce a voltage when mechanically stressed. When pressing the key no mechanical movement will be felt. This type of key/switch is particularly robust under rough conditions and is splash and scratch resistant.

Pressing a key produces a short beep tone but only results in an action if the desired operation is sensible. LEDs inside some keys indicate the current operational mode of the instrument. For extra user friendliness the indicators have been designed such that the operational mode is still visible even under difficult light conditions such as strong sunlight.

5.2.2. Display Contrast

The display contrast is preset in the factory and cannot be changed by the operator.

5.2.3. Grouping of Front Panel Controls

The front panel of the instrument consists of a piezo-crystal keyboard with 4 integrated LCD display and is divided into the following elements:

Displays • Seven segment display Capacitance / Inductance • Seven segment display Dissipation / Power Factor • Seven segment display Test Voltage / Current • Dot matrix display Test Mode

CAPACITANCE AND DISSIPATION / POWER FACTOR TEST SET

Tettex Instruments

PF

tan δ

DISSIPATION/POWER FACTORCAPACITANCE / INDUCTANCE

I

U test

TEST VOLTAGE / CURRENT

pF /mH

nF /H F /kHµ

X

kV

mAA

TEST MODE

SET IDENT OPT

POWER

C N

C N REF

INPUTtan /PF

20°Cδ

PRINTINTERFSUPPR

EXTINT

EXTINT

.

EXTINT PRINT

PRINT

PRINT

PRINT

PRINT

PRINT

PRINTENTER

TEST

20°C

RUNMODE

DISPMODE0

I f

QF QGSTg BUST B

UST A GSTg A

GSTgA+B

PI

SUST A+B GST A+B

7 8 9

4 5 6

31 2

Fe

SPACE

m



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Operating elements • Keyboard for Test Mode, measurement value definition / numerical keys • Selection of Test Mode / Display Mode • RUN (start the measurement) • Keyboard for input of system parameters

5.2.4. Display with Measurement Value Keys

The instrument has three LCD measurement value displays and a dot matrix display on which chosen measurement values can be displayed one under another. Keys next to the LCD displays are used to determine the measurement value to be displayed.

5.2.4.1. Capacitance / Inductance display

Figure 18: Capacitance / Inductance Display

This 4½-digit display shows the measured capacitance or inductance of the test object. A small horizontal dash on the right hand edge of the display indicates the unit of measurement.

The measuring bridge independently recognizes if the test object is capacitive or inductive. If the test object is capacitive then the dot matrix display TEST MODE shows a rotating CCC and if the test object is inductive then a rotating LLL is displayed. Using this information, it should be clear whether the units on the units display are F (Farad = capacitance) or H (Henry = inductance). The measurement values that are displayed are always those associated with the parallel equivalent circuit (see Chapter 4.6 Conversion Formulae Series & Parallel Equivalent Circuits).

If the rotating “LLL” or “CCC” is replaced alternately by a “R” it shows that the turns ratio for an external current comparator is set (≠1).

5.2.4.2. Dissipation / Power Factor display

Figure 19: Dissipation / Power Factor Display

This 4½ digit display shows the measured value of Dissipation Factor tan δ or Power Factor cos ϕ of the test object.

5.2.4.2.1. tan δ and PF (cos ϕ) measurement value keys

Pressing one of the keys next to the display (tan δ or PF) will cause the associated measurement value to appear. These keys have built-in LEDs that indicate which key is active.

If one of these keys is press twice then the associated measurement value will be displayed in percent.

CAPACITANCE / INDUCTANCE

pF /mH

nF /H F /kHµ

PF

tan δ

DISSIPATION/POWER FACTOR




5.2.4.3. Test Voltage / Current display

Figure 20: Test Voltage / Current Display

This 3½ digit display shows the measured test circuit voltage in kV or the test current IX through the test object in mA or A. A small horizontal dash on the right hand edge of the display indicates the unit of measurement.

5.2.4.3.1. Utest and IX measurement value keys Pressing one of the keys next to the display (Utest or IX) will cause the associated measurement value to appear. These keys have built-in LEDs that indicate which key is active.

When the measurement value has been selected, the instrument automatically selects the optimum measurement range.

5.2.4.4. Test Mode dot matrix display The backlit dot matrix display is a two-line multi-function display. This display shows measurement values (Display Mode), Test Mode, type of test object (capacitive or inductive), firmware version and menu-assisted parameter input, error messages and much more. Operation of this display is further described in Chapter 5.2.5 Operation elements. The following diagram shows a typical display during a measurement.

TEST MODE

UST A R3 CCf = 50.05 Hz A12

Test Mode

Internal measurement

Type of test objectin this case capacitive

Display Modeselectable by user

Dynamic averaging isactivated and will be calculatedfrom 12 measurement values

range (3...-1)

Figure 21: Test Mode display, typical measurement values

I

U test


X

kV

mAA



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5.2.5. Operating Elements

5.2.5.1. Test Mode keyboard, measurement values / numerical keys

Figure 22: Test Mode keyboard, measurement values / numerical keys

Nearly all the keys on this keyboard have double functions. There are, in total, three functions integrated into this keyboard, namely the TEST MODE (red), the measurement display DISPLAY MODE (blue) and the keys for alphanumeric entry (black). Choice of measurement type or the measurement value display is selected by using the following keys:

TEST MODE is selected by first pressing the red TEST MODE key. Similarly, the measurement values in the dot matrix display are selected by pressing the blue DISP MODE key.

5.2.5.1.1. Entering alphanumeric values The black alphanumeric keys are used for entering system parameters. Alphanumeric inputs can contain a maximum of 15 characters. The following keys are available:

„0...9“ „/“„ “„SPACE“ „è“ „ç“

Letters (e.g. description of test location) can be entered by using the arrow keys. Every press of the arrows produces a letter of the alphabet. The letters can be scrolled through by pressing the appropriate arrow key to scroll forwards or backwards through the alphabet. Pressing ENTER accepts the character and the cursor moves forward one space.

If a character (letter, number etc.) is to be deleted then scroll through the characters until ß appears. Pressing the ENTER key will then delete the character to the left of the ß.

Using the above instructions enter the desired characters e.g. description of test location, and end the character entry with the RUN key.

5.2.5.1.2. Type of measurement TEST MODE A special switching unit enables measurement of both earthed and floating test objects. Determination of dissipation factor tan δ and desired partial capacitance of test object depends upon the appropriate choice of the measurement type UST, GST or GSTg.

UST Ungrounded Specimen Test

.

EXTINT PRINT

PRINT

PRINT

PRINT

PRINT

PRINT

PRINTENTER0

I f

QF QGSTg BUST B

UST A GSTg A

GSTgA+B

PI

SUST A+B GST A+B

7 8 9

4 5 6

31 2

Fe

SPACE

m

TESTMODE

DISPMODE




GST Grounded Specimen Test Measurement of a test object earthed on one side. Low voltage electrode and housing

are connected to earth.

GST g Grounded Specimen Test with guarding Measurement of a test object earthed on one side, on which the undesirable partial

capacitance is eliminated by connection to the supply reference point v.

The designations A, B, A+B refer to the two available measurement channels A and B. A+B means that both channels are connected in parallel (further information is available in Chapter 7.3 Test Setup and Test Modes).

To choose a TEST MODE proceed as follows: TEST MODE

ENTER NEW TESTMODE (RED KEY’ s)

Press the red TEST MODE key and the display shown here to the left will appear. This display enables selection of the desired TEST MODE.

Press, for example, the GSTg A

6 key. TEST MODE

GSTg A 12 : 15f = 50.05 Hz

The chosen test mode is switched in and the display appears as shown.

TEST MODE

PLEASE: RED KEY!TRY AGAIN!

If an invalid key is pressed following the pressing of the TEST MODE key then the display will appear as shown to the left.

5.2.5.1.3. DISPLAY MODE Several additional measurement values can be selected by the user and shown on the dot matrix display:

S........ Apparent power of the test object

P........ Real power of the test object

Q ....... Reactive power of the test object

f ......... Frequency of system synchronization

When measuring inductance the following values are useful:

Im ....... Magnetizing current

QF ..... Quality factor

IFe....... Iron loss current

To choose the DISPLAY MODE proceed as follows:



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TEST MODE

ENTER NEW DISPMODE (BLUE KEYS)

Press the blue DISP MODE key and the display shown here to the left will appear. This display enables input of the desired measurement parameters.

Press, for example, the PRINT

Q

SPACE key. TEST MODE

UST A 12 : 15Q= 0.000mVAR

The selected measurement parameter will appear in the second line of the display.

TEST MODE

WRONG !TRY A BLUE KEY!

If an invalid key is pressed after DISP MODE has been pressed, then the display shown here to the left will appear.

5.2.5.2. Activating the measurement RUN After switching on the measurement bridge, the RUN button must be pressed once in order to activate the measurement. In addition, the RUN key has the function of storing the measurement value during the measurement (Hold Mode). The instantaneous measurement value will then be „frozen“. This means that all measurement values are retained and can be read from the display until the RUN key is pressed once more.

For safety reasons this is not valid for the high voltage display. Although all other measurement values are „frozen“, the current test voltage in kV will continue to be displayed. The update rate of the high voltage display is four times faster in Hold Mode.

Figure 23 Activating the measurement RUN

5.2.5.3. Keyboard for entering system parameters

Figure 24: System parameter keyboard

This keyboard is used to define all the system parameters that are necessary for the measurement. If entry of values is necessary then this is achieved using the alphanumeric keyboard as described in Chapter 5.2.5.2 Test Mode keyboard, measurement values / numerical keys.

20°C

RUN

SET IDENT OPT

POWER

C N

C N REF

INPUTtan /PF

20°Cδ

PRINTINTERFSUPPR

EXTINT

EXTINT




5.2.5.3.1. POWER mains switch The POWER switch is used to switch on the instrument.

!

Before switching on the measuring bridge, please read the safety advice in Chapter 2 Safety and ensure that the mains voltage selection switch is set to the correct position (Chapter 5.1.1).

5.2.5.3.2. Input of CN value Before a measurement can be performed, the exact capacitance value of the standard capacitor CN in pF must be programmed into the measuring bridge. As the entire measurement is dependent upon the quality of the standard capacitor, this value must be accurately known.

External standard capacitor CNext

First press the EXT/INT key so that the LED is lit. Now follow the operator instructions on the dot matrix display and, using the numerical keys (see Chapter 5.2.5.1), enter the exact capacitance value of the externally connected standard capacitor ending with the ENTER key. This value is not stored in the volatile

memory of the measuring bridge. When the measuring bridge is switched off, this values remains stored.

!

Warning:

When using the measuring bridge together with a dedicated Tettex Instruments Division high voltage supply (type 5283 or 5284), the choice of CNext disables the high voltage from being switched on.

The value entered must be greater than 10pF otherwise an error message will appear („Your input value is out of range“).

If an external standard capacitor is being used for measurement, then the applied high voltage must not exceed a maximum value, otherwise the measuring bridge may be damaged. For further information see Chapter 4.4.1 Maximum test voltage.

Internal standard capacitor CNint

If the measuring bridge is equipped with an internal standard capacitor (ca. 100pF/12kV) then this can be used for measurements, providing that the test voltage is not higher than 12kV. The exact capacitance value will have been entered in the protected non-volatile memory during factory calibration and cannot be changed by the operator. This fixed value can be displayed by setting the EXT/INT key to internal capacitance (LED is not lit) and then pressing SET.

For a quick overview, the individual measuring systems are described again below:

The following measuring bridges are equipped with an internal standard capacitor CNint:

Type 2818 (Field version: CNint 100pF/12kV built into measuring bridge)

Type 2818a (Laboratory version: CNint 100pF/12kV built into measuring bridge)

Type 2818/5283 (Complete test system: CNint 100pF/12kV built into measuring bridge)

Type 2816/5284 (Complete test system: CNint 100pF/12kV built into Control Unit)

Type 2816/5284U (Complete test system: CNint 100pF/12kV built into high voltage supply)

POWER

SET

C N

C N

EXTINT



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Page 37

The following measuring bridges are not equipped with an internal standard capacitor CNint:

Type 2816 Field version: measurements only possible with an externally connected standard capacitor CNext

Type 2816a Laboratory version: measurements only possible with an externally connected standard capacitor CNext

5.2.5.3.3. System reference EXT/INT If the measuring bridge and the high voltage supply are both connected to the same mains voltage, then REF INT (internal reference, LED unlit) should be selected. This means that the mains frequency (from the internal mains transformer) will be used for system synchronization. Further, the internal calibration of the measurement channels will be based upon an internal AC voltage.

If the test instrument and high voltage supply are connected to different supply networks with different frequencies (50/60 Hz), then REF EXT (external reference, LED lit) should be selected. This means that system synchronization is achieved using the measurement signal. Further, calibration of the measurement channels requires a correct test setup and a test voltage.

If the above requirements are met, then the Filtercheck (internal calibration procedure) commences and the system is ready for use after about 3 seconds. If the test voltage is too small then the following appears on the dot matrix display:

The message remains until either the test voltage is large enough for internal calibration or the reference selection is switched to internal.

!

Warning:

When using the measuring bridge together with a dedicated Tettex Instruments Division high voltage supply (type 5283 or 5284), the choice of REF EXT disables the high voltage from being switched on.

5.2.5.3.4. Test identification IDENT INPUT Pressing the IDENT INPUT key starts an identification-input dialogue. A test object can be described with up to 12 characters (numbers, spaces, slash, stop). This identification appears on all test reports. The internal clock can also be set using the IDENT INPUT key. The following inputs are possible:

1 = Serial Number Enter the serial number of the test object 2 = Object Description of the test object 3 = Set Time Enter the system time and date 4 = Site Description of test location or company

5.2.5.3.4.1. IDENT INPUT; (1 = Serial Number)

The serial number of the test object can be entered and saved in the test instrument. It remains stored when the instrument is switched off e.g. for printing of test reports at a later date.

REF

EXTINT

TEST MODE

SORRY! THERE ISNO INPUT SIGNAL !

IDENTINPUT




To enter the serial number of the test object proceed as follows:

TEST MODE

1 = Serial Number2 = Object 0=More

Press the IDENT INPUT key and the message to the left appears on the dot matrix display.

Select 1 = Serial Number (using the alphanumeric keys according to Chapter 5.2.5.1).

TEST MODE

1 = Serial Number_

Input the required serial number and end with the ENTER key.

The serial number may be up to 12 characters. The following keys are available for use:

„0...9“ „/“„ “„SPACE“ „è“ „ç“

5.2.5.3.4.2. IDENT INPUT; (2 = Object)

The type of test object can be entered and saved in the test instrument. It remains stored when the instrument is switched off e.g. for printing of test reports at a later date.

To enter the type of test object proceed as follows:

TEST MODE



Select 2 = Object (using the alphanumeric keys according to Chapter 5.2.5.1).

TEST MODE

.RUN=End OPT=Help

A flashing dot appears as a cursor in the upper line of the dot matrix display. The lower line advises the user that pressing the RUN key will complete the data entry and pressing OPT will provide user help.

The test object description may be up to 15 characters. The following keys are available for use:

„0...9“ „/“„ “„SPACE“ „è“ „ç“

Letters can be entered by using the arrow keys. Every press of the arrows produces a letter of the alphabet. The letters can be scrolled through by pressing the appropriate arrow key to scroll forwards or backwards through the alphabet. Pressing ENTER accepts the character and the cursor moves forward one space.


Using the above instructions enter the desired test object description and end the character entry with the RUN key.



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5.2.5.3.4.3. IDENT INPUT; (3 = Set Time)

To enter the system time and date proceed as follows:

TEST MODE



Select 0 = More (using the alphanumeric keys according to Chapter 5.2.5.1) to display further selection possibilities.

TEST MODE

3 = Set Time4 = Site 0 = More

By selecting 3 the procedure for input of date and time is started.

If the selection number 3 is already known by the user, then this can be directly entered without first selecting 0.

TEST MODE

YEAR ?XX

XX is the previously valid year.

Now enter the two-digit year number and finish with ENTER.

TEST MODE

MONTH ?XX

XX is the previously valid month.

Now enter the two-digit month number and finish with ENTER.

TEST MODE

DAY ?XX

Now the day (0...31 permitted) can be entered. Reach the next display by pressing the ENTER key.

TEST MODE

HOUR ? (0 ... 23)XX

Enter the hour and finish with the ENTER key.

TEST MODE

MINUTE ?XX

Input the minutes (0...59) and finish with the ENTER key.

TEST MODE

ACTUAL TIME IS :TT.MM.JJ SS:MM

The instrument now checks if a sensible date and time has been entered. This takes about 3 seconds. If the check is positive then the instrument is ready for use.

TEST MODE

IMPOSSIBLE INPUTTRY AGAIN !

If the data check is negative then the error message shown to the left is displayed. The instrument requests a correct date and time input. The procedure for data entry recommences.

5.2.5.3.4.4. IDENT INPUT; (4 = Site)

A description of the test location or similar information can be entered and saved in the test instrument. It remains stored when the instrument is switched off e.g. for printing of test reports at a later date.




To enter data proceed as follows:

TEST MODE




TEST MODE

3 = Set Time4 = Site 0 = More

Select 4 to start the data entry procedure for the test location description.


TEST MODE

.RUN=End OPT=Help

A flashing dot appears as a cursor in the upper line of the dot matrix display. The lower line advises the user that pressing the RUN key will complete the data entry and pressing OPT will provide user help.

The test location description may be up to 15 characters. The following keys are available for use:

„0...9“ „/“„ “„SPACE“ „è“ „ç“



Using the above instructions enter the desired test object description and end the character entry with the RUN key.



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5.2.5.3.5. Interference Suppression INTERF SUPPR Maintenance measurements on equipment in electrical utility substations are performed in environments of high voltage and current, which produce strong magnetic and electrical fields. Disturbance voltages can be induced in the test circuit with the result that measurement results can be completely false. Such influences can even altogether prevent a meaningful measurement.

The use of interference suppression is especially effective in environments with alternating magnetic and electric fields. For further information see Chapter 4.7.3 Interference Suppression.

The measuring bridge can independently determine which high voltage supply is connected. The interference suppression operation is determined according to the connected high voltage supply.

If a high voltage supply, specially designed by Tettex Instruments Division, is being used then the High Quality Mode (HQ Mode) can be employed. Such high voltage supplies are controllable from the bridge and the entire interference suppression (including coarse and fine balance) is performed automatically. This is possible with the following supplies:

• HV supply type 5283 for the type 2818 measuring bridge

• HV supply type 5284 for the type 2816 measuring bridge

• HV supply type 5284U for the type 2816 measuring bridge

If a customer specific high voltage supply, or not one of the above supplies, is connected then the HQ Mode is not available to the operator. Only the Standard Mode is then available.

5.2.5.3.5.1. Interference suppression in Standard Mode

Note: In order to achieve optimum interference suppression, the coarse and fine balance must always be performed.

Warning:

Interference suppression is only possible if the measuring bridge and high voltage supply are powered from the same mains voltage (same frequency and synchronized to each other).

Coarse balance

To activate the interference suppression proceed as follows: TEST MODE

IF U-TEST IS OFFPRESS RUN !

Press the INTERF SUPPR key (LED lights up) and the message shown to the left will appear, advising the user to first turn off the HV supply before pressing the RUN key. The HV supply must first be turned off, otherwise it will not be possible to differentiate between the interference and the measurement signal, and the measurement signal will also be suppressed.

TEST MODE

OKAY !PLEASE WAIT !

The message to the left appears after 6 seconds and advises the user to wait during the coarse balance.

INTERFSUPPR

!




TEST MODE

I =x.xxx mA Na XaN=VN X=VXi

The compensation vector values appear, which will be saved in the Cn and Cx registers. Ii ...............Suppressed interference current a...............Amplification channel N (a=0...4 means 100...104) b...............Amplification channel X (a=0...4 means 100...104) VN, VX.....Give the magnitudes of the interference vectors

The measuring system now measures the interference, calculates the interference compensation and then compensates. After this is complete, the interference vectors should become shorter and the amplification greater. In an ideal case the vector lengths would decrease to zero and the amplification of the N and X channels increase to maximum: Na = Xa = 4 (which means 104 =10000)

If a minimum interference vector length is reached during interference fluctuations, then the automatic interference suppression can be quit by pressing the INTERF SUPPR key once more. This internally freezes the values for interference suppression.

The procedure will automatically quit under problem-free interference conditions when the interference vector length reduces to zero..

TEST MODE

TOO HIGHINTERFERENCE !

The message shown to the left appears under extreme interference conditions or if the electronics responsible for interference suppression are defective.

The normal measurement mode will become active after around 3 seconds.

Having completed the interference coarse balance the operator can be assured that the greater part of any interference will be suppressed during subsequent measurements and that the instrument will measure the test object in accordance with the appropriate (internal) settings. When at least one measurement has been performed (HV ON, RUN), the internal settings of the microprocessor (range etc.) will be saved and the interference fine balance can be performed.

Fine balance

To perform the fine balance proceed as follows: TEST MODE

INTERF. -SUPPRESS.1=ADJUST 2=EXIT

Press the INTERF SUPPR key (LED is already lit) and the selection menu to the left appears on the dot matrix display.

1=ADJUST: The fine balance is activated by entering 1 and the procedure is the same as for the coarse balance.

2=EXIT: Entering 2 will switch of the interference suppression. Confirm with ENTER.

Warning:

Whenever the test mode is changed (UST, GST, GSTg ...), or if an unrealistic measurement result is obtained, the complete interference suppression procedure must be repeated (coarse and fine balance). !



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TEST MODE

IMPOSSIBLE WHILENOT MEASURING !

If ADJUST is selected without a prior measurement having been made, then an error message appears.

The normal measurement mode will be active again after around 3 seconds and the process can be repeated.

5.2.5.3.5.2. Interference suppression in High Quality Mode

A High Quality Mode (HQ Mode) is available for high voltage supplies that have been specially developed by Tettex Instruments Division for this measuring bridge. HQ Mode performs the entire interference suppression procedure fully automatically. The HQ Mode can be activated, providing that a suitable supply with Control Unit is connected to the measuring bridge, as follows:

TEST MODE

1= Standard Mode2= HQ Mode 3= Exit

Press the INTERF SUPPR key (LED lights up) and the selection menu to the left appears on the dot matrix display.

1=Standard Mode: Entering 1 activates the standard mode. See Chapter 5.2.5.3.5.1 „Interference suppression in Standard Mode.

2=HQ Mode: Entering 2 starts the fully automatic High Quality Mode.

3=EXIT: Entering 3 switches off the interference suppression.

TEST MODE

OKAY !PLEASE WAIT !

After pressing 2 this message appears requesting the user to wait.

TEST MODE

Set HIGH VOLTAGEthen press RUN

After another 5 seconds the user is requested to set the high voltage value on the connected high voltage supply and then to press RUN.

TEST MODE

HQ Mode startedEstem. Time 1 min

This display advises that the fully automatic HQ Mode will last for around 1 minute.

TEST MODE

OKAY !PLEASE WAIT !

After 3 seconds this display appears.

TEST MODE

HIGH VOLTAGEtoo low

If the high voltage setting is lower then 1kV then this error message appears. Set the voltage within the range 1kV ...12kV and press RUN once more.

TEST MODE

HQ Modein progress

The fully automatic HQ Mode process now runs. The following displays run automatically, simply advising the user of what is happening.




TEST MODE

Please wait

The coarse balance now follows.

TEST MODE


The compensation vector values appear, which will be saved in the Cn and Cx registers. Ii ...............Suppressed interference current a...............Amplification channel N (a=0...4 means 100...104) b...............Amplification channel X (a=0...4 means 100...104) VN, VX.....Give the magnitudes of the interference vectors

TEST MODE

Please wait

The fine balance now follows.

TEST MODE


The compensation vector values appear, which will be saved in the Cn and Cx registers.

TEST MODE

Please wait

TEST MODE

1st MeasurementLine STRAIGHT

The first measurement with normal voltage polarity is now performed.

TEST MODE

Please wait

The measurement values are saved.

TEST MODE

2nd MeasurementLine CROSSED

Now the second measurement is performed, whereby the voltage polarity is reversed.

TEST MODE

Please wait

The average value of the two test results is calculated.

TEST MODE

HQ ModePrinting results

The measurement in HQ Mode is now complete and the measurement values are printed out on the printer built into the control unit of the high voltage supply.

TEST MODE

To exit HQ Modepress INTERF SUP

When the measurement is completed, pressing the INTERF SUPPR key will exit the Interference suppression process.

The actual measurement values on the LCD display are actually related to the second measurement and the average values are



Operation Manual

Page 45

related to the second measurement and the average values are only visible on the printout.

TEST MODE

Set HIGH VOLTAGEthen press RUN

If it is desired to perform further measurements in HQ Mode, then set the high voltage supply to a new voltage value and press RUN to start interference suppression in HQ Mode once again.

5.2.5.3.6. Options OPT Pressing the OPT key produces a selection menu which gives access to various additional useful functions of the automatic measuring bridge. These can be programmed or activated and are described in detail below. The following selections are available:

1= DYN. AV.......... Dynamic Averaging

2= SETUP............ Instrument settings active at switch-on

3= To 10kV .......... Conversion of the measurement value to 10kV

4= Ratio ext. CC... Ratio of external Current Comparator

5= C serie............. Conversion between serial and parallel equivalent circuits

6= int. Printer........ Printer selection

7= Z...................... Calculation and display of the impedance Z

5.2.5.3.6.1. OPT 1; Dynamic Averaging DYN. AV

This function produces the dynamic average (see Chapter 4.7.5) from a number of measurement values (2...99). If the test voltage UTest is low (< 1kV with CN= 100pF), then the signal/noise ratio will be low and the measurement values will be unstable. On the assumption that the noise represents both an equal positive and negative part of the real measurement signal, averaging can produce an accurate and stable test result.

To activate the dynamic averaging function proceed as follows: TEST MODE

1=DYN. AV 2=SETUP3=To 10kV 0=MORE

After pressing the OPT key, select 1 from the menu (using the numerical keys as described in Chapter 5.2.5.1).

TEST MODE

AVERAGING CYCLES_1

Enter the number of measurement values from which the average is to be calculated (2...99) and finish with the ENTER key.

The display reverts to the normal measurement display. When RUN is pressed then AXX will appear on the left-hand side of the second line. This indicates to the user that averaging is switched on and XX shows the number of measurement values from which the average has already been calculated.

A second press of the RUN key empties the average memory and uses the next XX values for averaging.

To switch off the averaging, set the number of values from which the average is to be calculated to 0 or 1. Then proceed as if activating the averaging as described above.

OPT




5.2.5.3.6.2. OPT 2; Instrument settings at switch-on SETUP

Using SETUP the settings can be chosen which will come into effect immediately after switching on the POWER. Two types are selectable:

1= USER User settings

If the USER operator settings are activated, then all instrument settings (with the exception of the test current display) are saved that were active before the USER key was pressed. The next time the measuring bridge is switched on these settings are retained and the following message appears briefly:

2= SYSTEM System settings

If the SYSTEM settings are activated, then the instrument settings of the user are lost when the measuring bridge is switched off. The following system settings are preset: • Internal reference • Internal CN will be used for measurement (if available) • Display of tan δ (not PF) • Frequency display on the dot matrix display • External current comparator is reset i.e. ratio = 1 • Temperature correction deactivated • Test mode UST A • Internal strip printer deactivated • Dynamic averaging deactivated

The next time the measuring bridge is switched on the system settings are active and the following message appears briefly:

To select the instrument settings proceed as follows: TEST MODE



TEST MODE

SETS ON STARTUP:1=USER 2=SYSTEM

Now select with which settings the instrument should start up.

1=USER: The latest active instrument settings will be saved and retained when the instrument is switched on again.

1=SYSTEM: At switch on the measuring bridge will be started with the predefined system parameters.

The selection is active immediately after pressing the selected key and the display will revert to the measurement display.

5.2.5.3.6.3. OPT 3; Conversion to 10kV

Some test objects have a maximum permissible test voltage of much less than 10kV. For comparison purposes, measurement values are desirable at 10kV for Real Power P and Iron

TEST MODE

USER setting`sare active !

TEST MODE

SYSTEM defaultsare active !



Operation Manual

Page 47

Loss Current IFe. The instrument facility for automatic conversion to 10kV is provided for just such cases.

This conversion is based upon the formula given in the appropriate standards (ANSI/IEEE C57.12.90):

PP kV

UTest10

2

2

10=

⋅ ( )( )

II kVUTest

1010

=⋅

Key UTest...... Test voltage P .......... measured Real Power at UTest P10........ Converted Real Power at 10kV IFE......... Measured Iron Loss Current at UTest I10 ......... Converted Iron Loss Current at10kV

To activate the automatic conversion to 10kV proceed as follows: TEST MODE



TEST MODE

Correct to 10 kV ?1=Do it 2=Do not

Select 1 to activate the automatic conversion to 10kV.

Selecting 2 will deactivate the automatic conversion to 10kV.

The selection is active immediately after pressing the selected key and the display will revert to the measurement display.

If the conversion is activated then the converted values can be displayed as follows:

If display of P or IFE is selected using DISP MODE, then the actual measured value is shown on the dot matrix display.

Selecting P or IFE a second time will display the converted value as P10 or I10 .

All values P, P10, IFE and I10 appear on all test reports as long as the conversion is activated.

5.2.5.3.6.4. OPT 4; External current comparator ratio - Ratio ext. CC

When measuring large capacitances (or small inductances), where the maximum measurement current of 15A will be exceeded, the range must be extended by use of an external current transformer (See Chapter 5.4.4). As the test current IX which flows in the bridge is no longer actually the current flowing through the test object, the measurement display must be converted according to the ratio of the current comparator.

The ratio of the external current comparator is entered as follows: TEST MODE


Press the OPT key and the message to the left appears on the dot matrix display.





TEST MODE

4 = Ratio ext CC5 = C serie 0 = More

Select 4 to choose the external current comparator.


TEST MODE

1 = Input Ratio2 = No ext CC

Select 1 to start the procedure for entry of the external current comparator ratio.

If 2 is selected this means that there is no external current comparator connected. The ratio will then be automatically set to 1.

TEST MODE

Input CC Ratio !1

After 1 is selected this menu appears for input of the ratio.

Enter the correct value (using the alphanumeric keys) and finish with ENTER.

All measurement value displays will now automatically show the converted measurement values. If the ratio is different to 1, then this will be indicated in the dot matrix display by the flashing C (or L) being alternately replaced with an R.

If the measuring bridge is switched off and the system settings are active (see Chapter 5.2.5.3.6.2), then the ratio which has been input will be reset.

5.2.5.3.6.5. OPT 5; Conversion between series / parallel equivalent circuits - C serie

Many customers use measurement bridges for insulation measurement that use a series equivalent circuit for the test object (e.g.. Tettex Measuring bridge type 2801). The measuring bridge described here is based upon a parallel equivalent circuit. See Chapter 4.6 Conversion Formulae Parallel & Series Equivalent Circuits.

As different measured values of capacitance may be obtained for an identical test object depending upon the equivalent circuit diagram used, this function offers a conversion. In this way the measurement values obtained for CX, with various measuring bridges can be compared.

Procedure to display series capacitance CS : TEST MODE




TEST MODE

4 = Ratio ext CC5 = C serie 0 = More

Select 5 to display the series capacitance.


TEST MODE

UST A R 0 CCCCs = 1.121 nF

Here is a display with conversion activated.

The calculated series capacitance value is shown in the second line, whilst the capacitance display still shows the appropriate measurement value (parallel equivalent circuit).



Operation Manual

Page 49

To switch back the conversion function, select another display mode. The conversion is now deactivated and the newly chosen value will be displayed.

5.2.5.3.6.6. OPT 6; Printer selection - int. Printer

This function is only useful when the measurement bridge is combined with a matching Tettex supply (HV Supply type 5283 for the measuring bridge type 2818 or HV Supply type 5284 for the measuring bridge type 2816), as a strip printer is built into the additional control unit. There is no printer built into the measuring bridge itself.

When a test report is produced by pressing the PRINT key (see Chapter 5.2.5.3.8 Producing test reports PRINT), all connected printers are activated. If the measuring bridge is also connected to an external printer then this will also be activated.

As it normally makes no sense to produce a test report simultaneously on two printers, namely on both the external and built-in printer, the strip printer can be switch on or off as follows:

TEST MODE




TEST MODE

6 = int . Printer7 = Z 0 = More



TEST MODE

Internal Printer 1 = ON 2 = OFF

Select 1 (ON) to switch on the internal printer.

Select 2 (OFF) to switch off the internal printer.

5.2.5.3.6.7. OPT 7; Calculation and display of impedance Z

Activating this function displays the impedance of the test object in Ohms. This function is activated as follows:

TEST MODE




TEST MODE

6 = int . Printer7 = Z 0 = More



TEST MODE

UST A R 0 CCCZ = 2.121 Ohm

Here is a display with conversion activated.

The calculated impedance value Z in Ohms is shown in the second line of the dot matrix display.




5.2.5.3.7. Conversion of tan δ or PF to reference temperature If a test object is measured, the temperature of which is not 20°C, then the dissipation factor tan δ (or PF) can be converted to a value referenced to 20°C. A conversion table for mineral oil in accordance with ANSI C 57.12.90 is provided as standard. As the conversion factors for different test objects can vary greatly, there is a facility provided for saving 7 tables in the protected memory of the instrument.

5.2.5.3.7.1. Entering conversion tables (1= NEW TAB)

Remove the write protection (see Chapter 6.2 Write Protection for the Non-volatile Memory) and switch the instrument back on.

TEST MODE

Input of: 1 = CN2 = OILTAB 3 = EXIT

The display shown left appears.

Select 2

TEST MODE

1= NEW TAB 2= EDIT3= DELETE 4= EXIT

Select 1 from the input menu to enter a new table.

TEST MODE

NO FREE MEMORYFIRST DELETE ONE

If the memory is used up, i.e. 7 tables are already saved, then an error message will appear.

TEST MODE

FACTOR AT 0 °C0

Now enter the conversion factor from 0°C to 20°C and finish with ENTER. Further questions regarding factors from 5°C to 90°C will appear. If a conversion factor is unknown, then simply accept the proposal of the microcomputer and press ENTER. During later calculation a linear interpolation will be applied, despite any missing factors. When 20 factors have been entered the oil table can be provided with an identifier.

TEST MODE

INPUT NAME OFOIL - TABLE !

This display now appears.

TEST MODE

ARUN=END OPT=HELP

After around 4 seconds this display appears for input of the table identification.

The blinking character can be changed with the arrow keys (è,ç).

The identification can contain a maximum of 15 characters. The following keys are available:

„0...9“ „/“„ “„SPACE“ „è“ „ç“



Using the above instructions enter the desired description and end the character entry with the RUN key.



Operation Manual

Page 51

TEST MODE

ARUN=END OPT=HELP

A user comment can be called up by pressing the OPT key (see display).

After about 3 seconds the display automatically reverts to the input mode.

When entry of the table description is completed, the input mode must be closed with the RUN key.

TEST MODE

INPUT OF: 1= CN2= OILTAB. 3= EXIT

This display appears. Select 3.

TEST MODE

PLEASE REPROTECTMY MEMORY !

This display appears until the write protect is reactivated (see Chapter 6.2 Write Protection for the Non-volatile Memory).

5.2.5.3.7.2. Changing conversion tables (2= EDIT)

If the write protect is inactive (see Chapter 6.2 Write Protection for the Non-volatile Memory) and if INPUT OF: OILTAB and then EDIT is selected after switch-on, then the table to be changed must first be activated with NEXT. When the table identification appears in the dot matrix display, each factor can be change by pressing EDIT.

The factors appear in the dot matrix display with the relevant temperature. If a factor is to be changed, it can be simply overwritten. If a factor should remain unchanged then it can be confirmed by pressing ENTER. At the end the name of the oil table will be asked for. This can also be edited, as described in the previous section. Return to normal measurement mode is achieved as described in the previous section.

5.2.5.3.7.3. Deleting conversion tables (3= DELETE)

Conversion factor tables are saved in the protected part of the non-volatile memory. In order to delete a table the write protect must be removed (see Chapter 6.2 Write Protection for the Non-volatile Memory). The following menu appears:

TEST MODE

Input of: 1 = CN2 = OILTAB 3 = EXIT

Select 2.

TEST MODE


Select 3 from this menu.

TEST MODE

TABLE 11= DELETE 2= NEXT

TABLE 1 stands for a previously entered table description. Choosing 2 searches for the table to be deleted.

Selecting 1 will delete the table whose description appears in the menu.

TEST MODE

THERE ARE NOMORE OIL TABLES

2=NEXT can be selected as many times as there are tables saved. If NEXT is selected and there are no more tables then an error message appears for 3 seconds.




TEST MODE


Select 4 in this menu.

TEST MODE

PLEASE REPROTECTMY MEMORY !

This display appears until the write protect is reactivated (see Chapter 6.2 Write Protection for the Non-volatile Memory).

5.2.5.3.7.4. Conversion of tan δ referenced to 20°C - tan δ /PF 20°C

If a conversion table is not entered, then pressing the tan δ / PF 20°Ckey directly activates the ANSI standard table. The following request appears:

TEST MODE

INPUT TEMP.20 °C

The test object temperature must now be input and finished with ENTER. If just ENTER is pressed or 20°C given then the conversion will be deactivated (the factor is always 1 for 20°C).

The lit LED in the tan δ / PF 20°C key shows that the conversion is activated. The recalculated values appear on all test reports. If a conversion table has been input then the display upon pressing the tan δ / PF 20°C key is as follows:

TEST MODE

ANSI NORM TABLE1= YES 2= NEXT

Select YES to use the displayed conversion table.

Select NEXT to find the desired conversion table and confirm with YES.

TEST MODE

INPUT TEMP.20 °C

Now enter the test object temperature again and finish with ENTER.

TEST MODE

YOUR INPUT VALUEIS OUT OF RANGE

If a temperature is entered which lies outside the range of table values then this error message appears. The normal measurement mode is resumed after about 3 seconds, without conversion (the LED in the tan δ / PF 20°C key goes out)

TEST MODE

1= NEW TEMP2= EXIT

If the conversion is still active (the LED in the tan δ / PF 20°C key is lit)then pressing the tan δ / PF 20°Ckey produces this display:

Selecting 2 (EXIT) will deactivate the conversion.

Selecting 1 will go to the next menu for entry of a new test object temperature.

TEST MODE

INPUT TEMP.XX °C

Enter the new test object temperature and finish with ENTER.

tan /PF20°C

δ



Operation Manual

Page 53

5.2.5.3.7.5. Extracts from standard ANSI/IEEE C57.12.90 -1993

5.2.5.3.7.5.1. Formula for recalculation at 20°C

The temperature correction factors for tan δ or power factor PF of insulation is dependent upon the insulating material, the material structure, the moisture content etc. The values for the correction factors are typical values and are sufficient for use in the following equation:

PFPF

Kmt

20 = or tantan

δ δ

20 =mt

K

PFp20 ...... Power factor at 20°C

PFmt........ Power factor measured at test object temperature T

tan δ 20 ... tan δ at 20°C

tan δ mT... tan δ measured at test object temperature T

K ............ Correction factor

5.2.5.3.7.5.2. Temperature correction factors

Conversion table for mineral oil as insulating fluid.

Test object temperature

Correction factor

T [°C] K

10 0.80 15 0.90 20 1.00 25 1.12 30 1.25 35 1.40 40 1.55 45 1.75 50 1.95 55 2.18 60 2.42 65 2.70 70 3.00

Note: The correction factors given above are valid for insulation systems that use mineral oil as the insulating fluid. Other insulating fluids may require different correction factors.

5.2.5.3.8. Producing test reports PRINT Pressing the PRINT key produces a test report on a connected printer. If the measuring bridge is combined with a matching Tettex supply (HV supply type 5283 for measuring bridge type 2818 or HV supply type 5284 for measuring bridge type 2816) the printout will be produced by the printer that is built into the supply. This built-in strip printer can be switched off via the OPT menu and 6 key (see Chapter

PRINT




5.2.5.3.6.6).

5.2.5.3.8.1. Connecting an external printer

If the measuring bridge is to be used without one of the above mentioned Tettex HV supplies, then an external printer can be connected to the PRINTER interface on the rear panel of the instrument.

The test report consists of a report header and 6 columns for measurement values. The header contains the date and time, and the fields LOCATION, OBJECT and SERIAL NO that can be entered using IDENT INPUT. The first measurement value column always contains the TEST MODE and the second contains the test voltage. The measurement values printed in the other four columns depend upon the test object (C or L) and the display mode (DISP MODE). If activated, the converted tan δ (or PF) value with associated temperature in °C appears on an additional line. A report header always appears when S10 PRINT is first pressed after switching on or after a new test object identification (IDENT INPUT) has been entered. To prepare a report header for a printout it is also sufficient to press the key S12 IDENT INPUT twice.



Operation Manual

Page 55

5.2.5.3.8.2. Useable Printers

In principle, all printers with a serial interface (RS232) can be used. The baud rate of the printer must be set to 2400 Baud. The baud rate of the measuring bridge is fixed at 2400 Baud and cannot be changed. Figure 25 shows a sample measurement test report on a DIN A4 page.

Figure 25: Test report printout, DIN A4 paper format

The above test report was produced on the following printer:

HP Think Jet, Model 2225 DQ




5.3. Basic Test Circuit

The basic test circuit is presented in order to be able to carry out a measurement. The actual test circuit may vary according to application.

Figure 26: Basic test circuit for C tan δ measurement

Key:

UTest ........High voltage supply (e.g. high voltage transformer)

CN ...........Standard capacitor

CX ...........Test object

E.............Earth connection

G ............Null detector

µP...........Microcomputer

∼vCX CN

G

P

Type 2816 / Type 2818

N1 N2

NI

CNCX UTest

E

µ



Operation Manual

Page 57

5.4. Typical Procedure

Periodic measurement of dissipation factor tan δ on HV motors in service gives information about the condition of the insulation (see Chapter 16.2 Measurements on a Machine with 2 pole Externally Configurable Winding System ).

The test method and maximum limit values for dissipation factor tan δ and its trend, in conjunction with the test voltage, are specified in the relevant recommendations and standards: VDE 0530, part I, 72.IEC 34-1, CENELEC - Document 345, IEC 216, IEEE STD: 286-1975 and Bull. SEV 54 (1963) S. 279 - 288.

International standards require, as the most important quality assurance criteria for rotating machines, measurement o dissipation factor tan δ at 0.2 – 0.4 – 0.6 – 0.8 – 1.0 UN and higher.

Preparation and typical measurement procedure are described below:

• Observe safety precautions! • The user is responsible for safety! • Disconnect and earth the test object according to user instructions. • Put the test system together and make the cable connection between the test instrument

and the high voltage supply. • Make a solid and clean connection between the HV GND of the test instrument and the earth

terminal of the test object using the earth cable (yellow/green). • Remove the mains supply to the test object. • Connect the test object according to the desired test circuit e.g. for a transformer:

− Every winding group must be short-circuited. − Connect the high voltage cable HIGH to those winding groups that are to be

considered as the high voltage electrode of the capacitance to be measured. − Connect the low voltage cable LOW A (or LOW B) to those winding groups which

are to be considered as the low voltage electrode of the capacitance to be measured.

• Connect the measuring system to the mains. • Remove the earth from the high voltage terminal before the measurement. • After a successful measurement ground the high voltage terminal once again.

5.4.1. Typical Measurements on Transformers

One of the most important application areas of the C tan δ measuring system is condition / maintenance measurement of transformers. These measurements are specified in the USA standard ANS/IEEE C57.12.90 (1987). Comments: • All terminals of the individual windings must be accessible. • The following table shows the capacitances which will be measured according to the

selection of test mode: • Windings that are not being used for the measurement should be either short-circuited or

connected to the v point, depending upon the test method. • The transformer must be reconnected for each winding and test capacitance to be

measured.




5.4.2. Use with Additional Components

As described in Chapter 14 Accessories and Options, Tettex Instruments Division offers a broad range of additional products to assist with measurement.

An specially developed test cell is available for determination of dissipation factor tan δ and dielectric constant εr of solid insulating material samples such as paper and synthetic foil or liquid insulants such as oil. In addition, the test cell can determine specific resistance.

A temperature control instrument (type 2967) has been developed for this test cell for heating the test medium in the test cell to a specific temperature. In this way it is possible to control the temperature of a test sample in accordance with VDE requirements 0303, 0311 and 0345.

Current comparators are available for extension of the measuring bridge’s maximum current range when measuring very large capacitances. (see Chapter 4.4.3 Maximum Test Current and Chapter 7.4 Measurements with Test Current greater than 15A (with Current Comparator).

5.4.3. Choosing the Ideal Standard Capacitor CN

For choice of the ideal value of standard capacitor see Chapter 4.5 Determination of Standard Capacitor Requirements. Tettex Instruments Division provides a broad range of standard capacitors.

5.4.4. Choice of the Ideal Current Comparator for Range Extension

The choice of ideal current comparator depends upon the maximum test current that will flow through the test object. This current depends upon both the test object capacitance and the maximum test voltage. For further information see Chapter 4.4.3 Maximum Test Current“ and Chapter 7.4 Measurements with Test Current greater than 15A (with Current Comparator).

Bridge 2816, 2818 The Microprocessor System


Operation Manual

Page 59

6. The Microprocessor System

6.1. General Construction

The microprocessor system built into the measuring bridge consists of the following units:

• 1 Processor 8085: Microprocessor

• 2 MUART: I/O-Ports and serial interfaces

• 8 kB RAM: Read-write memory

• 8 kB NVRAM Non-volatile memory

• 32 kB EPROM Program memory for firmware

The non-volatile memory stores the user defined system parameters (e.g. CN value) so that the instrument doesn’t „forget“ them. Half of this non-volatile memory is protected to avoid inadvertent overwriting. This write-protect may only be removed to change the value of the internal CN or to enter an oil conversion table for recalculation of tan δ values. The measurement system cannot function without this write protection.

6.2. Write Protection for the Non-volatile Memory

The write protection is activated or deactivated by removing the short-circuit link on the 8085-3 microprocessor. Proceed as follows:

1. Open the front panel of the instrument by loosening the four screws (1) and turn the locking device underneath the black cover (2). The front panel can then be opened like a door (3) (see Figure 27).

2. Pull the 8085-3 pcb card out slightly.

The write protection is active when the jumper J4 is in the PROTECT position, otherwise the write protection is inactive (see Figure 28).

!

Warning:

Highly sensitive CMOS devices are located on the microprocessor card. The components on this card should not, therefore, be disturbed (danger of damage!). To switch off the write protection it is therefore recommended to just pull the processor card slightly out of the rack and to remove the short-circuit link with a pair of tweezers or similar.

The Microprocessor System Bridge 2816, 2818



Figure 27: Opening the front panel

6.3. Switch Designations on the Microprocessor Card

Figure 28: Microprocessor card switch locations

Switch bank S2:

Switch 1...6 and 8: No function

Switch 7 ON: Internal printer (of high voltage supply) is inactive

OFF: Internal printer (of high voltage supply) is active

CAPACITANCE AND DISSIPATION / POWER FACTOR TEST SET

Tettex Instruments

PF

tan δ

DISSIPATION/POWER FACTORCAPACITANCE / INDUCTANCE

I

U test


pF /mH

nF /H F /kHµ

X

kV

mAA

TEST MODE

SET IDENT OPT

POWER

C N

C N REF

INPUTtan /PF

20°Cδ

PRINTINTERFSUPPR

EXTINT

EXTINT

.

EXTINT PRINT

PRINT

PRINT

PRINT

PRINT

PRINT

PRINTENTER

TEST

20°C

RUNMODE

DISPMODE0

I f

QF QGSTg BUST B

UST A GSTg A

GSTgA+B

PI

SUST A+B GST A+B

7 8 9

4 5 6

31 2

Fe

SPACE

m

2

1

1

1

1

3

Bridge 2816, 2818 The Microprocessor System


Operation Manual

Page 61

6.4. Non-volatile Memory Power Supply

The supply for the non-volatile memory is a lithium battery with a life expectancy of around 5 years. If the battery runs out, then the microprocessor detects this and an error message appears on the dot matrix display:

TEST MODE

CONSTANT-MEMORYSUPPLY IS EMPTY

and after about 3 seconds

TEST MODE

NEED URGENTSERVICE

The test instrument can still be used, but the system parameters must be entered by the user every time the instrument is switched on.

If you wish to order a new battery from Tettex instruments then please quote the following order number:

Battery order number: 7-017557-00-0

The Microprocessor System Bridge 2816, 2818



Bridge 2816, 2818 Constructing the Test Circuit


Operation Manual

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7. Constructing the Test Circuit

This chapter contains important information regarding construction of the test circuit and the individual test modes. Selected circuits for specific test objects are presented for further information. Unfortunately it is not possible to provide a test circuit for every customer specific test object as this would exceed the capacity of this manual.

If this chapter is read carefully, and the function of the measuring bridge with the individual test modes is understood, then it will be simple to find the relevant test circuit for a special application.

7.1. Operating Personnel

Although the operation of the equipment is similar to a computer, the operating personnel require no special knowledge of computer operation. As a result of menu driven parameter input and monitoring of entries, the instrument operation is very simple, and as a result operation is actually self-explanatory.

7.2. Tips for Setting-up the Test Circuit

7.2.1. Location of the Instrument

The instrument may be used in any position. It is recommended that the instrument is not placed for a long duration on a heat-emitting surface or in direct sunlight.

The C tan δ measurement bridge should be placed on a desk of sufficient height. If the instrument is to be used with a Tettex HV supply, then Tettex Instruments supplies a transportation trolley specially designed for field use.

7.2.2. Connection to System Earth

The connection between system earth and the earth screw terminal on the rear panel of the instrument should be made with a copper braid and kept as short as possible.

The instrument must be connected to the mains voltage (115VAC or 230VAC) with the mains cable supplied.

!

Warning: Before the instrument is switched on, especially before high voltage is supplied to the test system, be sure to read the safety advice.

For construction of a suitable test setup please read the following chapter.

Constructing the Test Circuit Bridge 2816, 2818



7.3. Test Setup and Test Modes

In order to achieve correct results the test setup must be tidy and the correct test mode for the application must be selected.

!

It is absolutely essential to have knowledge of the various test modes that can be selected from the keyboard and the method of operation for using the measuring bridge.

The following basic diagram for testing a transformer with three windings should fully explain the available test modes and their application (see Figure 29).

7.3.1. Important points when selecting the correct Test Mode

• The correct test mode must connect the capacitance to be measured to the internal measurement input (int. ME).

• Partial capacitances that are not to be measured must be connected to the v point of the test system.

• Knowledge of the circuit, especially the equivalent circuit diagram of the test object, is very helpful for choosing the correct test mode.

• When measuring in the modes GST and GSTg, the high voltage conductors to the test object (which are connected for normal use) must definitely be disconnected, otherwise the capacitance of the inductors to earth will also be measured.

• The connection between HV GND on the measuring instrument and the earth point of the test object is also a measurement connection. For this reason a good clean contact is essential.

7.3.2. Important points about the HV Supply

To perform the required measurement always requires a HV supply and a standard capacitor (See Chapter 4 Technical ). The customer has the choice of using his / her own HV supply or a specially developed supply from Tettex Instruments Division.

Customer specific supplies are of an advantage when the test voltage lies above 12kV. Measurements up to and above 100kV can be performed using a suitable external standard capacitor (see Chapter 4 Technical Overview) and an appropriate HV supply.

In order to use an external supply with the test modes GST and GSTg it is essential that the supply is double-screened. This double screening eliminates the stray capacitance of the HV supply and avoids false measurement results. Further, it should be ensured that the grid-to-plate capacitance (capacitance between HV and earth) is as small as possible. Further information is available upon request. The supply v point must always remain unearthed.

Higher test currents can also be achieved when using a suitable external HV supply. The measuring bridge can work directly with test currents up to 15A. Significantly higher currents can be measured by use of an external, high precision current comparator (see Chapter 14.1.3 Current comparators for range extension).



Operation Manual

Page 65

7.3.3. Test Mode

Figure 29: Basic C tan δ measuring system test setup for a transformer with two low voltage windings

Test Mode Internal instrument connections Measured capacitance CX

INPUT A to INPUT B to HV GND to

UST A int. ME v v CHA UST B v int. ME v CHB UST A + B int. ME int. ME v CHA + CHB GST A + B int. ME int. ME int. ME CHA + CHB + CHG GSTg A v int. ME int. ME CHB + CHG GSTg B int. ME v int. ME CHA + CHG GSTg A + B v v int. ME CHG

Test Mode

Internal instrument switch positions

S1 S2 S 3A S 3B S 4A S 4B HV GND → V HV GND → int. ME INPUT A→ int. ME INPUT B→ int. ME INPUT A → V INPUT B → V

UST A closed Open Closed Open Open Closed UST B closed Open Open Closed Closed Open UST A+B closed Open Closed Closed Open Open GST A+B Open closed Closed Closed Open Open GSTg A Open closed Open Closed Closed Open GSTg B Open closed Closed Open Open closed GSTg A+B open closed Open Open closed closed

Note: The HV cable and measurement cable should be exchanged for testing the secondary winding insulation against earth; the HV cable should be connected to the secondary winding and the measurement cable to the primary winding. The measured capacitances in the table will, of course, change accordingly.

HIGH VOLTAGE TO TEST OBJECT

INPUT A

INPUT B

HV GND

S 3A

S 3B

S 2

S 4A

S 4B

S 1

v

N NNX

Type 2816/5284U

U test

int. ME

Type 2818/5283

CHB

CHA

CHG

A

BH

G

TEST OBJECT

CNint

Available test modes:

UST Ungrounded Specimen Test GST Grounded Specimen Test GSTg Grounded Specimen Test

with guarding




7.3.4. Description of the individual test modes

7.3.4.1. Test Mode UST for ungrounded test objects This test mode is the most normal situation when measuring capacitance and dissipation factor. Various ungrounded capacitances can be measured using this mode, providing that the maximum test current of the measuring bridge is not exceeded.

When measuring transformers and HV current transformers, this configuration determines the capacitance and dissipation factor between the various winding groups.

7.3.4.2. Test Mode „GST“ for earthed test objects This test mode enables the measurement of capacitances that are normally earthed on one side when in operation. When measuring transformers‚ this configuration measures the capacitance and dissipation factor between the HV winding and all other windings and the transformer housing.

7.3.4.3. Test Mode „GSTg“ for earthed test objects with screen circuit This test mode directly measures the capacitance between the HV terminal and the housing (which is earthed). The partial capacitances that are undesirable for the measurement are connected to the supply reference point v and thereby rendered ineffective.

When measuring transformers‚ this configuration measures the capacitance and dissipation factor between the various winding groups and the transformer housing. The windings which are not used for measurement are connected to the v terminal of the measuring system via the A (or B) measuring cable.

7.3.5. Advantages of the Selectable Test Modes

When measuring transformers and other test objects the problem often arises that, in addition to the „normal“ ungrounded capacitances, capacitances with one side grounded must also be measured (e.g. capacitance between a winding and an earthed housing). Conventional measurement systems require the external test setup to be changed for such measurements. This can involve a lot of work, especially when on-site measurements are being perform on large power transformers.

Using the test modes, the test object only has to be connected once for measurement and all relevant capacitances can be measured by switching the test mode as required.



Operation Manual

Page 67

7.3.6. Measurements with a Customer Specific Supply with Test Object Current less than 15A

7.3.6.1. Standard test circuit

Figure 30: Standard test circuit

Key

.................. Neutral system earth, to which the grounded test object is connected (e.g. transformer housing)

Input A ............ Measurement input A Input B ............ Measurement input B HV GND.......... Earth terminal of the measuring bridge v...................... Reference point of the HV supply CNext ................ Terminal for the external standard capacitor CD ................... Grid-to-plate capacitance of the HV supply between HV and earth (should be as

small as possible as this can falsify measurement values) High voltage HV terminal for the HV electrode of the internal standard capacitor

v

CN

G

µ

Type 2816 Type 2818

P

Test Mode Switching

CNint

Only in Type 2818

HighvoltageCN extInput B A

∼

CHB CHA

HV GND

HV

CHG

CD




7.3.6.1.1. Comments on the above test circuit The test circuit in Figure 30 illustrates the measurement principle. It is valid for both the 2816 and 2818 series. If the measurement principle is understood, then it is actually clear how the terminals of various test objects should be connected.

The 2818 series can use an external standard capacitor CNext in addition to an internal standard capacitor CNint as the measurement standard.

The internal standard capacitor CNint can then be used as long as the applied test voltage does not exceed 12kV. This means that the HV can be connected directly to the High Voltage terminal of the measuring bridge. In addition, all the conditions described in Chapter 4.5 Determination of Standard Capacitor Requirements must be fulfilled.

An external standard capacitor CNext can then be used mainly when the test voltage is greater than 12kv or if the conditions for the internal standard capacitor, as described in Chapter 4.5 Determination of Standard Capacitor Requirements, are no longer fulfilled.

!

Warning: When using the measuring bridge series 2818, never connect both standard capacitors (CNint and CNext) during the measurement. Otherwise measurement errors will result even though the correct standard has been selected on the measuring bridge.

7.3.6.1.2. Test modes and measured capacitances in Figure 30 The following table shows the capacitances that will be measured according to the selection of test mode:

Test Mode Capacitance measured CX

UST A CHA

UST B CHB

UST A + B CHA + CHB

GST A + B CHA + CHB + CHG

GSTg A CHB + CHG

GSTg B CHA + CHG

GSTg A + B CHG



Operation Manual

Page 69

7.3.7. Maintenance Measurements on Transformers in Accordancewith USA Standard ANSI/IEEE C57.12.90-1993

The following points must be observed when performing measurements in accordance with the ANSI/IEEE C57.12.93 standard:

• All possible capacitances2 must be measured i.e. capacitance between the individual winding systems; capacitance of the winding systems to the transformer housing (earth).

• All windings must be immersed in oil.

• Each winding group must be short-circuited.

• All bushings must be installed.

• The temperature of windings and the insulating fluid (oil) should be close to the reference temperature (20°C).

• The test voltage should not be more than half of the low frequency working voltage or 10kV.

The necessary measurement can be easily performed with the 2816/5284U and 2818/5283 measurement systems i.e. every measurement can be made with and without guarding circuit. As explained previously, all capacitances can be measured without changing connections by simply switching the TEST MODE as required.

2 ...... For further details see ANSI/IEEE C57.12.93 standard (Table 1: „Measurements to be made in insulation Power-Factor tests“




7.3.7.1. Measuring a single-phase autotransformer with tertiary winding

Figure 31: Measurable capacitances of an autotransformer with tertiary winding

The following table shows the capacitances that will be measured according to the selection of test mode:


UST A CHT

UST B -

UST A + B CHT

GST A + B CHT + CHG

GSTg A CHG

GSTg B CHT + CHG

GSTg A + B CHG

Conditions: − All terminals of the individual windings must be accessible − None of the windings may be connected to earth (transformer housing) on one side.

Note: The HV cable and measurement cable should be exchanged for testing the tertiary winding insulation against earth CTG; the HV cable should be connected to the tertiary winding and the measurement cable to the primary winding. The measured capacitances in the table change accordingly.

CTG

CHT

CHG

H

G

TEST OBJECT

HV GROUND

INPUT AHighVoltage

Transformer casing (Tank)

A

CHT .........Capacitance between the HV winding and the tertiary winding

CHG ........Capacitance between the HV winding

and the transformer housing (tank connected to earth)

CTG.........Capacitance between the tertiary

winding and the transformer housing (tank connected to earth)



Operation Manual

Page 71

7.3.7.2. Measuring a transformer with two windings

Figure 32: Measurable capacitances of a transformer with two windings

The following table shows the capacitances that will be measured according to the selection of test mode:


UST A CHL

UST B -

UST A + B CHL

GST A + B CHL + CHG

GSTg A CHG

GSTg B CHL + CHG

GSTg A + B CHG

Conditions: − All terminals of the individual windings must be accessible − None of the windings may be connected to earth (transformer housing) on one side.

Note: The HV cable and measurement cable should be exchanged for testing the secondary winding insulation against earth CLG; the HV cable should be connected to the secondary winding and the measurement cable to the primary winding. The measured capacitances in the table change accordingly.

CLG

CHL

CHG

G

TEST OBJECT

HV GROUND

INPUT A or BHighVoltage

Transformer case (Tank)

Low voltage sideHV side




7.3.7.3. Measuring three-phase transformers

7.3.7.3.1. Star-star formation

Figure 33: Measurable capacitances of a three-phase transformer, Yn – Yn formation


UST A CHL

UST B -

UST A + B CHL

GST A + B CHL + CHG

GSTg A CHG

GSTg B CHL + CHG

GSTg A + B CHG

G

TEST OBJECT

HV GROUND

INPUT A or B

HighVoltage



CHLC

HGCLG



Operation Manual

Page 73

7.3.7.3.2. Star-delta formation

Figure 34: Measurable capacitances of a three-phase transformer, Yn-∆ formation

Test Mode Measured capacitance CX

UST A CHL

UST B -

UST A + B CHL

GST A + B CHL + CHG

GSTg A CHG

GSTg B CHL + CHG

GSTg A + B CHG

G

TEST OBJECT

HV GROUND

INPUT A or B

HighVoltage



CHLC

HGCLG




7.4. Measurements with Test Current greater than 15A (with Current Comparator)

7.4.1. General information on Range Extension

When measuring with high test voltages and / or with large test object capacitances, with which the test current IX exceeds the maximum permissible input current of the measuring bridge, an external current comparator (CT3) must be used for range extension.

When using an external current comparator for range extension, the accuracy of the bridge will be reduced, depending upon the quality of the current comparator used.

In addition, additional errors will occur depending upon the test mode applied. It should therefore be considered, from case to case, which test mode should be used.

7.4.2. Errors caused by External Current Comparators

7.4.2.1. Correction formula for tan δ and CX

7.4.2.1.1. Influence of the current error F[%] The current error mainly influences the capacitance measurement, as the secondary current magnitude varies from the value it should be.

The computerized correction is performed according to the following formula:

Cx CxF

corr measI

= ⋅ +( )1100

[%]

The polarity of the current error must be considered.

7.4.2.1.2. Influence of the error angle δ [min] The error angle influences the dissipation factor measurement, as the secondary current varies by this angle from the value it should be.

The effective measured value of dissipation factor tan δ is calculated according to the following formula:

tan tanδ δδ

corr measI

= +3440

[Minutes]

Key: FI ..........conversion error of the range extension current transformer in % δI...........phase error of the external current transformer in minutes corr .......corrected value meas ....measured value

3.......CT = Current Transformer



Operation Manual

Page 75

Example: A conventional current transformer (comparator) of Class 0.1 produces the following error:

Error angle δI : ± 1 Minute Conversion error FI : ± 0,1% Measured value CX = 100nF, tan δ = 1 • 10-3 The following errors can be calculated for these measurement values:

Cxcorr = 100nF ± 01 100

100, ⋅ nF

= 100nF ± 100pF

tan δcorr =1 • 10-3 ± 1

3440= 1 • 10-3 ± 2.9 • 10-4

From the above calculations it can be seen that the capacitance measurement must be corrected by 0.1% and the dissipation factor tan δ by 2.9 • 10-4. Of course, the errors must be considered at every point of use.

7.4.3. Recommendations

From the considerations and examples in Chapter 7.4.2.1 it is clear that the tan δ measurement is already considerably worsened by use of an external current transformer for range extension with an error angle of 1 Minute. For accurate measurements, therefore, it is recommended to use our precision current transformer (current comparator) Series 4760.

The errors are then reduced to a very low level by electronic compensation. Typical value are:

Phase error δ [min]: ± 0.05 Min

Current error F[%]: ± 0.002%

As these errors are extremely small, their influence upon capacitance and dissipation factor tan δ measurement can normally be considered as negligible.




7.4.4. Measurements with an External Current Comparator (IX > 15A)

Figure 35: Measurement setup with external current comparator (IX > 15A)

Select Test Mode UST A.

CT ........Current transformer (comparator) series 4760

CX

UTest

∼

∼

L

K

k

l

CN

Twisted cablesCT

u

v

G

µ

Type 2816 Type 2818

P

Test Mode switching

CNint

Only in Typ 2818

HighvoltageCN extInput B A HV GND



Operation Manual

Page 77

7.4.5. Accuracy Considerations when using a Current Comparator

When using the test setup described in Chapter 7.4.4 measurement errors will arise, but they are normally negligible. Nevertheless, an explanation is included in this manual for completeness.

7.4.5.1. Influence of current CN The current CN flows through the primary winding of the external current transformer on its way back to the supply transformer (HV). The displayed measurement value of capacitance is

therefore too large. For large CC

X

N ratios this error can be neglected. This is apparent in the

following example.

Example:

Given: External standard capacitor CN = 1000 pF Current comparator with conversion ratio R = 100 (500 / 5A) Using maximum measurement range = R 1000 CN = 100 µF

When measuring a test object with CX = 100 µF the CX error will be

FCC

CxN

X= =

⋅⋅

= ⋅ =−

−−1000 10

100 1010 10 0 001%

12

66 ,

When measuring a test object with CX = 10 µF the CX will be

FCC

CxN

X= =

⋅⋅

= ⋅ =−

−−1000 10

10 10100 10 0 01%

12

66 ,

7.4.5.2. Errors due to stray capacitance When using the test setup in Figure 35 the additional dissipation factor tan δ of CX, caused by the conductor resistance of the connection cable to the current comparator, is eliminated by connection of v directly with CX.

As the v terminal of the measuring bridge is not earthed, so can the influence of the cable capacitance upon CX not be defined. For this reason, the cable between CX and the current comparator should be kept as short as possible. The stray capacitances will be reduced by the short cable and are subsequently negligible, bearing in mind that the test capacitance when using a current comparator is considerably large.




Bridge 2816, 2818 Getting Started


Operation Manual

Page 79

8. Getting Started

8.1. Preparations Before the Measurement

The following preparatory checks and setups are necessary with the Type 2816 and 2818 measuring instrument

a) Check that the mains voltage cable supplied is plugged in. On safety grounds no other cable may be used.

b) The test object must be disconnected and earthed in accordance with the manufacturer’s advice.

c) Calculate the maximum expected measurement current IX as advised in Chapter 4.4.3 Maximum test current.

d) Choose whichever measurement setup is most suitable for the application (according to Chapter 7.3.6 Measurements with a customer specific supply with test object current less than 15A and Chapter 7.4 Measurements with test object current greater than 15A (with current comparator)).

e) Construct the measurement setup. Partial capacitances that are not to be measured should be connected to the v point of the test arrangement.

f) Check that absolutely all safety requirements have been observed.

8.2. Switching on the Instrument

Before switching on, the following important points should be remembered:

♦ observance of safety regulations, especially VDE 0100 and VDE 0104;

♦ visual inspection of earthing connections to the instruments in the test system;

♦ visual inspection of earthing connections to the safety barrier (e.g. wire mesh) around the danger area;

♦ check that nobody is within the danger area.

!

Before connecting the instrument to the mains voltage it is absolutely essential that the correct mains voltage (115VAC or 230VAC) has been selected with the mains selector switch.

The POWER mains switch is located on the front panel of the instrument.

Getting Started Bridge 2816, 2818



After switching on it will take about 15 seconds while the instrument initialises and it is then ready for use.

TEST MODE

TETTEXINSTRUMENTS


TEST MODE

SYSTEM defaults are activ !


TEST MODE

FILTERCHECK : A= 0.949 P= -0.017


TEST MODE

UST A 17:29f= 50.04 Hz

Figure 36: Displays during the instrument initialization

A warm-up time of 5 minutes is recommend to measure with full accuracy

8.3. Instrument Settings for Measurement

Although the instrument is ready for measurement immediately, it is recommended first to make a few settings to match the instrument to the test setup.

In addition to the measurement displays, which can be selected as tan δ, PF, Utest and IX for example, further settings may be necessary for some test setups.

8.3.1. Settings on the Measuring Bridge Series 2816

a) Enter the exact capacitance value of the externally connected standard capacitor, as described in Chapter 5.2.5.3.2

b) Input of CN . If the matching high voltage supply Type 5284U (with built-in CN) is connected, then the input of the standard capacitor value is unnecessary.

c) If a current comparator is being used for range extension, then the conversion ratio must be entered, as described in Chapter 5.2.5.3.6.4 OPT 4; External current comparator ratio - Ratio ext. CC .

d) If a test report is produced using a printer, then entering the test identification is useful (see Chapter 5.2.5.3.4 Test identification IDENT INPUT).

e) If useful functions, such as averaging or changes to the standard settings, are required then see Chapter 5.2.5.3.6 Options OPT.

f) Select the desired Test Mode (e.g. UST A ), raise the test voltage to the desired value and press the RUN key.



Operation Manual

Page 81

g) Now all the desired measurement values will be either directly readable or can be seen by pressing the appropriate key combination. A manual balance of the bridge is unnecessary, as this will be automatically performed.

8.3.2. Settings on the Measuring Bridge Series 2818

a) This step is only necessary if it has been decided not to use the internal standard capacitor and an external standard capacitor has been connected instead. Enter the exact capacitance value of the externally connected standard capacitor, as described in Chapter 5.2.5.3.2 Input of CN . The lit LED in the CN key shows that the external standard capacitor will be used as a reference.

b) If a current comparator is being used for range extension, then the conversion ratio must be entered, as described in Chapter 5.2.5.3.6.4 OPT 4; External current comparator ratio - Ratio ext. CC .

c) If a test report is produced using a printer, then entering the test identification is useful (see Chapter 5.2.5.3.4 Test identification IDENT INPUT).

d) If useful functions, such as averaging or changes to the standard settings, are required then see Chapter 5.2.5.3.6 Options OPT.

e) Select the desired Test Mode (e.g. UST A ), raise the test voltage to the desired value and press the RUN key.

f) Now all the desired measurement values will be either directly readable or can be seen by pressing the appropriate key combination. A manual balance of the bridge is unnecessary, as this will be automatically performed.




8.4. Menu Structure (Brief Operation Guide)

This chapter serves as an overview of the menu structure for entry of system parameters. For more detail see Chapter 5.2.5.3 Keyboard for entering system parameters.

The arrows indicate which display or action follows after pressing the appropriate key. It is recommended to copy the following page and to use this menu structure as a brief operation guide.

8.4.1. Choice of Standard Capacitor CN

EXTINT Choice of standard capacitor C N

SET

CN

TEST MODE

INPUT CN - EXTERN_ pF

Display of CNext

TEST MODE

PROTECTED VALUE!95.1759 pF

C Next

C Nint

Input of CNext

Standard

Capacitorapprox. 3 seconds long

8.4.2. System Reference C N

EXTINT

Switching of system reference (only possible with external supply)REF

IDENT OPT

POWER

SET

CN

INPUTtan /PF

20°Cδ

PRINTINTERFSUPPR

REF

EXTINT

CN

EXTINT



Operation Manual

Page 83

8.4.3. Choice of Connected Printer

PRINT

TEST MODE

THERE ARE NO VALUES TO PRINT

YES

NO

Test report on ext. printer only

Valuesavailable?

OPT 6OFF

ON

Test report on int. and ext. printer

8.4.4. Entering the Measurement Identification

1 = SERIAL NUMBER

2 = Object

3 = SET TIME

4 = SITE

Enter the serial number

Enter the test object identification

System time input menu

Measurement location info.

IDENTINPUT




8.4.5. Optional Functions

1 = DYN. AV

2 = SETUP

3 = To 10 kV

4 = Ratio ext. CC

Dynamic averaging input menu

Definition of instrument settings

Conversion to10 kV

Conversion ratio input menu

at switch-on

for external current comparator

5 = C Serie

6 = int. Printer

7 = Z

Conversion between serial andparallel equivalent circuits

Switching test report on / offinternal printer

Display of impedance Z

OPT

(Dissipation factor & loss current)

8.4.6. Input and Selection of Oil Factor Tables

TEST MODE

INPUT TEMP.30 °C

YES

NO

Scroll through conversion tables with 2

desired

available ?

Enter the test objecttemperature which the conversion

factor table

TEST MODE

TEST MODE

ANSI NORM TABLE1 = YES 2 = NEXT

INPUT TEMP.20 °C table is to work.

Enter the test object temperature with which tocalculate the ANSI / IEEE standard.

tan /PF20°C

δ



Operation Manual

Page 85

8.4.7. Choice of Interference Suppression

Interf.

YES

NOSupply

Type 5283 Suppr. or

Type 5284 U Only Standard Mode possible

1 = Standard Mode

1 = ADJUST

2 = EXIT (Cancel)

(Fine balance LED in INTERF. key must light)

Coarse balance performed

1 = Standard Mode

2 = HQ Mode

TEST MODE

TEST MODE

SET HIGH VOLTAGEThen press RUN

HIGH VOLTAGEtoo low

RUN

NO

Now in HQ Mode

HV >= 1000 V

YES

2 = HQ Mode




Bridge 2816, 2818 Care and Maintenance


Operation Manual

Page 87

9. Care and Maintenance

The Type 2816 / 2818 Measuring Bridge is basically service free, as long as the specified environmental conditions are adhered to. As a result, service and maintenance is restricted to cleaning of the equipment and calibration at intervals stipulated by the application for which the instrument is used.

The insulation of all high voltage cables should be periodically checked for damage. If any damage to the insulation is detected then a new measurement cable should be ordered from Tettex Instruments Division.

If the instrument is to remain unused for a long time then it is recommended that steps are taken to prevent ingress of dust inside the housing through air circulation (i.e. wrap or pack the instrument).

If the instrument is to be used in extreme environmental conditions (e.g. unclean, oily air with airborne metal or coal dust, high humidity etc.) then it should be protected by building into a suitable housing with forced air filtering or similar suitable protection. If such protective measures cannot be provided, then the instrument should be periodically checked for contamination and

promptly cleaned with suitable cleanser when required. This kind of service work is particularly important if high voltages are to be measured and should be performed by an authorised service agent.

9.1. Cleaning the Instrument

The instrument should be cleaned with a lint free cloth, slightly moistened using mild household cleanser, alcohol or spirits. Caustic cleansers and solvents (Trio, Chlorothene etc.) should definitely be avoided.

Advice: In particular, the protective glass of the display should be cleaned from time to time with a soft, moist cloth such as used by opticians. Marking of the glass by touching with the fingers should be avoided.

9.2. Instrument Calibration

When delivered new from the factory, the instrument is calibrated in accordance with the calibration report provided. A periodical calibration of the instrument every two years is recommended.

As the calibration process is fairly extensive, the instrument can only be calibrated and, if necessary, adjusted at Tettex Instruments Division’s factory. An updated calibration report will then be issued.

!

Care and Maintenance Bridge 2816, 2818



Bridge 2816, 2818 Trouble Shooting


Operation Manual

Page 89

10. Trouble Shooting

For further information regarding error messages that may appear on the display of the Type 2816 / 2818 measuring instrument see Chapter 18 Appendix C: Locating Faults. If persistent problems or faulty operation should occur then please contact the Customer Support Department of Tettex Instruments Division or your local agent.

The Customer Support Department of Tettex Instruments Division can be reached at the following address:

Customer Service Department

Haefely Test AG

Tettex Instruments Division

Bernstrasse 90, P.O. Box

CH-8953 Dietikon - Zurich

Switzerland

Tel: +41 1 744 74 74

Fax: +41 1 744 74 84

e-mail: sales @tettex.com

In addition, see our Home Page for current information.

Home Page: http://www.tettex.com

Trouble Shooting Bridge 2816, 2818



Bridge 2816, 2818 Instrument Storage


Operation Manual

Page 91

11. Instrument Storage

During day to day use the instrument can be switched off at the mains switch located above the mains socket on the rear panel of the instrument.

If the instrument is to remain unused for any length of time, it is recommended to unplug the mains lead. In addition, it is advisable to protect this high precision instrument from moisture and accumulation of dust and dirt with a suitable covering.

Instrument Storage Bridge 2816, 2818



Bridge 2816, 2818 Packing and Transport


Operation Manual

Page 93

12. Packing and Transport

The packing of the Type 2816 or 2818 C tan δ Measuring Bridge provides satisfactory protection for normal transport conditions. Nevertheless, care should be taken when transporting the instrument. If return of the instrument is necessary, and the original packing is no longer available, then packing of an equivalent standard or better should be used.

Whenever possible, transport the C tan δ measuring bridge in a waterproof container. Protect the instrument from mechanical damage during transport with padding ( min. 5cm ). Mark the container with the pictogram symbols „Fragile“ and „Protect from moisture“.

Figure 37: Pictograms on the transport container

12.1. Taking Delivery

When taking delivery, any possible transport damage should be noted. A written record should be made of any such damage. A suitable remark should be recorded on the delivery documents.

A claim for damage must be reported immediately to the transport company and to the Customer Support Department of Tettex Instruments Division or the local agent. It is essential to retain the damaged packing material until the claim has been settled.

12.2. Proof of Despatch

Check the contents of the shipment for completeness immediately after receipt. If the shipment is incomplete or damaged then this must be reported immediately to the transport company and the Customer Support Department of Tettex Instruments Division or the local agent. Repair or replacement of the instrument can then be organised immediately.

12.3. Scope of Delivery

On receipt, check the instrument and accessories mechanically and for conformance with the delivery documents. Inform the delivery company of any damage and missing parts of the shipment.

Packing and Transport Bridge 2816, 2818



Bridge 2816, 2818 Recycling


Operation Manual

Page 95

13. Recycling

When the instrument reaches the end of its working life it can, if required, be disassembled and recycled. No special instructions are necessary for dismantling.

The instrument is constructed of metal parts (mostly aluminium) and synthetic materials. The various component parts can be separated and recycled, or disposed of in accordance with the associated local rules and regulations.

Recycling Bridge 2816, 2818



Bridge 2816, 2818 Accessories and Options


Operation Manual

Page 97

14. Accessories and Options

This chapter describes the accessories that can be used in conjunction with the type 2816 and 2818 measuring bridges. Contact us directly if you have a special application, as the following list is only a part of the broad range of accessories available.

14.1. Options

The following accessories can be delivered as an option, depending upon the application and the customer’s request:

14.1.1. Measurement and Interface Cables

Type 5991 Interface cable for RS 232C Interface

Type 5992 fibre optic cable for RS 232C interface

Type 5945 interface converter RS 232C/IEEE 488

Type 101 WK cable to test object Cx: single pole, single shielded with connecting box, standard lengths 2, 5, 10, 20 m

Type 101 W cable to standard capacitor CN: single pole, single shielded with right-angle connector, standard lengths 2, 5, 10, 20 m

Nr. 4-16343-00 Nr. 4-16351-00 Nr. 4-16399-00

earthing cable, 16 mm²: Length 5m earthing cable, 16 mm²: Length 10m earthing cable, 16 mm²: Length 20m

Nr. 4-16430-00 Nr. 4-16431-00 Nr. 4-16432-00

v – supply cable, 10 mm²: Length 5m v – supply cable, 10 mm²: Length 10m v – supply cable, 10 mm²: Length 20m

14.1.2. External Standard Capacitor

3320 series Air standard capacitor

Type 3370 Nk/1000/30 Pressurized gas standard capacitor 1000 pF/30 kV

Type 3370NK/100/100 Pressurized gas standard capacitor 100 pF/100 kV

3370 series Pressurized gas standard capacitor 200 kV - 1200kV

14.1.3. Current Comparators for Range Extension

Type 4762 Maximum primary current: 400A



Accessories and Options Bridge 2816, 2818



14.1.4. High Voltage Supplies

5270 series High voltage supplies to requested specification

Type 5251 Resonant supply max. 2000V

Type 5285 High voltage supply 0...12kV/2.4kVA, with built-in standard capacitor 100pF/12kV

Type 5286 Additional supply for type 5283 and 5284 100V/10A (specially for inductance measurement)

Type 5288 Resonant supply for type 5283 and 5284 for increased test current up to max. 4.4A

14.1.5. Measurement Cells

Measurement cells for liquid insulants:

Type 2903

Type 2905

Heatable to 150 °C max. 2000V

Test cell max. 1000V

Measurement cells for solid insulants:

Type 2914

Heatable to 300 °C max. 2000V

Type 2967 Heating equipment for measurement cells type 2903 and type2914

14.1.6. Software

SWSEQ Software „Sequence“ for data collection and test report generation

Bridge 2816, 2818 Revisions and Corrections


Operation Manual

Page 99

15. Revisions and Corrections

Nr. Date Description

1 22.12.99 Extended description of Chapter 5.2.5.2 Activating the measurement RUN on page 35

2 5 April 2001

Addition of chapter 20.2 Views of the Type 2816/5284 Measuring Bridge and Accessories

3 11. April 2002

Wiring diagram of chapter “17.10.1 RS-232 Computer Interface“ changed.

4

5

6

7

8

9

10

Revisions and Corrections Bridge 2816, 2818



Bridge 2816, 2818 Appendix A: Test Circuit Examples


Operation Manual

Page 101

16. Appendix A: Test Circuit Examples

16.1. Introduction

This chapter is intended to demonstrate to the user the versatility of the Type 2818 and 2818 Measuring Bridge. The following test circuits illustrate various applications. These circuits serve simply as examples and may be adapted for special applications by the user.

Various types of documents containing background information are available to customers, on request from Tettex Instruments Division, regarding further applications:

Application Solution for a particular measurement problem; application of a standard test method to energy apparatus by means of a Tettex equipment family.

Solution Tettex solution to a particular customer problem by application of one or more test methods to energy apparatus (= engineering project).

Information Theoretical discourse regarding the use of an equipment family / test method in a specific area.

Procedure Short description of a test method on a (group of) test object(s) with an instrument / system according to a standard.

Appendix A: Test Circuit Examples Bridge 2816, 2818



16.2. Measurements on a Machine with 2 pole Externally Configurable Winding System

With this test setup it must be ensured that that stator is earthed. The following test setup is also suitable for stator windings on high power motors U > 10 kV, P>10MW.

Figure 38: Example of test circuit for a machine with 2 pole externally configurable winding system

*....... Open windings must be short circuited and connected to v. Connection to earth would result in the measurement of additional stray capacitance.

UTest HighVoltage

HV GROUND

INPUT A

INPUT B

Test object Cx



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16.3. Measurement of Short Circuit Impedance in Accordance with IEC 76-5

Figure 39: Measurement of short circuit inductances

16.3.1. Measurement Procedure

If a complete measurement system type 2816/5284U or 2818/5283 is available, then these measurements can be simply performed by using the „Current Booster“ type 5286. The „Current Booster“ is an additional supply that delivers currents up to 10A at low voltage (10V/100V) and can be directly plugged into and operated from the control unit.

When measuring short-circuit impedance it is essential to calculate the equivalent series inductance. Press the „OPT“ key on the measuring bridge and then „5“ (see Chapter 5.2.5.3.6.5 OPT 5; Conversion between series / parallel equivalent circuits - C serie).

16.3.2. Interpretation of Results

The measurement of short-circuit inductance of transformers doesn’t just give information about the stray inductance of the coil itself. Percentage changes in inductivity, compared to earlier measurements or manufacturer’s specifications, can indicate changes in geometry.

Changes of between 2…4% in ZX generally mean a change in coil geometry or coil compression. Values between 4…6% and over indicated damage to the winding. The phase symmetry of multi-phase transformers should always be checked.

L XP

G

TEST OBJECT

HV GROUND

INPUT A or B

HighVoltage

Transformator case (Tank)

Low voltage side

HV side

L XS




16.4. C tan δ testing of High Voltage Cables

vCX CNext

G

P

Type 2816 Type 2818

N1 N2

NI

CN

UTest

u

CX

Cable termination

HV Supply

µ

Input A or B

~

Figure 40: Circuit for C tan δ measurement of high voltage cables

Select test mode UST A.



Operation Manual

Page 105

16.5. Measurement of High Voltage Bushings

HIGH VOLTAGE

TO TEST OBJECT

INPUT A

INPUT B

HV GND

Type 2818/5283

Test ModeMeasured

UST A

UST B

C

- -

D

capacitance

G

CD

Type 2816/5284U

Figure 41: Circuit for measurement of bushings




16.6. Dissipation Factor Measurement on Single-phase Shunt Reactors4

Type 2816a or 2818aCnvCxACxB

Standard CapacitorTest object

Current comparator

K

L

l

k

HV Power Supply~

Figure 42: Block schematic diagram for measurement of single-phase shunt reactors

The following measurement values can be measured and reported using the type 2816 and 2818 measuring bridges:

− Test voltage Utest − Parallel and series inductance Lx

− Test frequency f − Quality factor QF

− Dissipation factor tan δ

− Power factor PF cos ϕ

− Magnetization current Im − Reactive power Q

− Iron loss current Ife − Real power P

− Test current Ix − Apparent power S

Practically all of these values can be used according to IEC 289. The following values are of particular importance for this application:

Utest, f, tan δ, LX, IX

4 ......A shunt reactor is connected in parallel to compensate for capacitive currents (reactive current) of a system (e.g. HV

busbars). See IEC 289 “Reactors“



Operation Manual

Page 107

16.7. Power Loss Measurements on Three-phase Shunt Reactors with External Terminals

2816a or 2818aCnvCxACxB

StandardCapacitor

Test object

Current comparator

Power supply

K

L

l

k

Neutral

Neutral

Neutral

Phase A B C

~

Figure 43: Block schematic diagram for measurement of three-phase shunt reactors

In order to measure other phases, the current comparator and the standard capacitor CX must be connected to the appropriate circuit. All three phases must be supplied with current in order to achieve normal operating conditions, but the measurement is performed per single phase.




Bridge 2816, 2818 Appendix B: Interfaces


Operation Manual

Page 109

17. Appendix B: Interfaces

17.1. Remote Control via IEEE 488 or RS232 Interfaces

The instrument can be completely remote controlled. All possible front panel settings can also be made via remote control (except interface configuration and print functions). In addition, all measurement data that can be displayed on the screen is also retrievable.

17.2. Introduction

This appendix described the command set used by the instrument. The syntax is according to the IEEE 488.2 standard.

Note that the programming required will vary in depth, depending upon the master computer and the application. It is therefore highly recommended that an overview of the remote functions be gained before proceeding with programming.

The instrument can be placed in local or remote control condition. Switching of the status is achieved by the appropriate command.

17.3. IEEE 488 Bus Structure

IEEE 488 - 1978 is an internationally accepted specification that defines the mechanical and electrical connections between all IEEE 488 compatible instruments. The standard describes a standard format for data and commands without specifying the instrument-specific programming, i.e. without specifying how an instrument should react to a specific command. Physically, the IEEE bus consists of 16 bi-directional passive conductors or wires, which can be connected to up to 15 instruments (including controller). The 16 wires can be divided into 3 groups: − 8 data lines − 5 control lines − 3 handshake lines

Appendix B: Interfaces Bridge 2816, 2818



Figure 44: Diagram of interfaces between three different instruments and IEEE bus

Every instrument within an IEEE 488 bus system must be IEEE operable in one or more ways.

17.3.1. Controller:

Addresses the other instruments as LISTENER or TALKER. It contains a system dependent program that organizes the measurement sequence and data exchange of the individual instruments.

17.3.2. Talker:

An instrument that can only send data on the bus and cannot receive data.

17.3.3. Listener:

An instrument that can only receive data and can’t send data on the bus (e.g. printer). The simplest example of an IEEE 488 bus system is a two component system that consists of a test instrument and a connected printer.

17.4. Setting the IEEE Address

The IEEE address can be set on the IEEE interface board of the type 2816 /2818. The factory default address setting is 8. If it is required to change the address, then the front panel must be

Device 1

talkerlistenercontroller

e.g. HP-85

Device 2

talkerlistener

Type 2793

Device 3

listener

e.g. Printer

e.g.

ser. 5970

Data Bus(8 signal lines)

Data 1 to 8

DAVNRFDNDACIFCATNSRQRENEOI

transfer control bus (handshake)3 signals lines

management bus3 signals lines



Operation Manual

Page 111

opened (as described in Chapter 6.2) and the DIL switch set on the IEEE board according to the following diagram. The instrument will operate in TALK and LISTEN MODE.

Figure 45: Setting the address of the IEEE interface

17.5. Concept for Commands and Responses

All the commands that the instrument can interpret consist of three characters. The first character can be:

? to query something from the instrument (e.g. CN value, TEST MODE etc.) S (Set) to enter a value (e.g. CN value, external current comparator ratio etc.) C (Change) to alter a setting (e.g. Disp MODE, Ref int to Ref ext etc.) V (Voltage) to control the high voltage (2818 only together with type 5283). X to send test to the dot matrix D4 and to activate the internal beeper. H High Interference Suppression

The second and third characters define the function. All messages that the instrument sends on the IEEE bus consist of an outgoing code with a following response so that they can be simply worked with by computer. All commands are acknowledged by a response.

17.6. Additional Command Set for RS-232

The IEEE-488 interface does not require a command for communication as it is clear from the address which instrument is being communicated with.

If the measurement system is to be used via the RS-232 interface, then the instrument must be set to remote or local condition.

IEEE Parameter

ON

OFF

IEEE Adresse

Talk and Listen

(e.g. 8)

12345678

22 03




Function characters

Meaning

REM Sets the measuring bridge to remote condition

LOC Sets the measuring bridge to manual or local condition

17.7. Command Set

Possible 1st character

Function character

Meaning

? AA Query the number for average calculation

? or S AC Query how many or sets the number of measurement values, from which the average is to be calculated

S A0 Sets the number for average calculation to zero (start averaging from new)

C or S or ? CE Change to CN EXT or set the CN EXT value or request the CN EXT value

C or ? CI Change to CN INT or request the CN INT value

? CN Query which CN is active (INT or EXT)

? CX Query the test object capacitance in pF

? CL Query if the test object is inductive or capacitive

? LX Query the test object inductance (in H)

? DM Which DISP MODE is active?

C

C

C

C

C

C

C

D1

D2

D3

D4

D5

D6

D7

Change to DISP MODE apparent power S

Change to DISP MODE real power P

Change to DISP MODE reactive power Q

Change to DISP MODE frequency F

Change to DISP MODE magnetization current Im

Change to DISP MODE Quality factor QF

Change to DISP MODE iron loss current IFe



Operation Manual

Page 113


Function character

Meaning

? FQ Query measurement frequency in Hz

? IX Query test object current in A

? IM Query magnetization current in A

? IF Query iron loss current in A

C or ? TD Query tan δ or change to tan δ display

C or ? PF Query power factor PF or change to PF display

? QF Query Quality factor QF

? PS Query apparent power S in VA

? PQ Query reactive power Q in Var

? PP Query real power in W

? UT Query test voltage in kV

? RS Query measurement result CX or LX, tan δ or PF, test voltage Utest

? RF Query which reference is active (INT or EXT)

C RI Change to internal reference

C RE Change to external reference

? S RT Query or set the conversion ration of an external current comparator

S R1 Set the conversion ratio of the external current comparator to 1

? TM Which TEST MODE is selected?

C

C

C

C

C

C

C

T1

T2

T3

T4

T5

T6

T7

Change to TEST MODE UST A

Change to TEST MODE UST B

Change to TEST MODE UST A + B

Change to TEST MODE GST A + B

Change to TEST MODE GSTg A

Change to TEST MODE GSTg B

Change to TEST MODE GSTg A + B

S SG Activate interference suppression and coarse balance

S SM Save the internal settings in preparation for the fine balance

S SF Fine balance





Function character

Meaning

S SQ Quit the balance (coarse and fine)

S SE Switch off interference suppression

H QM Activate HQ interference suppression (without reporting results)

H QP Activate HQ interference suppression (with reporting of results)

H QC Deactivate HQ interference suppression

C PC Change to switched polarity

C PS Change to normal polarity

V ON High voltage ON

V OF High voltage OFF

V UP * Raise high voltage

V DN * Lower high voltage

V SP * Stop raising or lowering of the high voltage

S HV * The high voltage will alter independently to the defined value XX.X (in kV). The voltage value XX.X follows directly after the command

X DM * * All characters that follow this instruction will be shown on the dot matrix display, without interrupting the test procedure.

X DE The dot matrix display is released once again for system messages

X BH The instrument emits a high beep tone

X BL The instrument emits a low beep tone

* .......These commands are only possible for the 2818 measuring bridge together with the 5283 high voltage supply

* *.....The dot matrix display consists of two lines of 16 characters. The change of line is normally performed automatically. If it is desired to switch line during a text message then this can be achieved by inserting the character #. Example: The # character in the string “Hello#How is it going?“ has the result that the word “Hello“ will appear on line 1 and the following characters “How is it going?” will appear on line 2.



Operation Manual

Page 115

17.8. Error Messages via the Interface

Message Cause Help

*0! OK ! Everything is alright, the last command sent was performed

*1! TOO LONG STATEMENT

The character chain sent is greater than 40 characters (e.g. CN with more than 40 positions)

*2! NOT POSSIBLE WITH CN- OR REF EXTERNAL !

It is not possible to work with the internal high voltage supply, if CNext or REF/EXT is selected

Select CNint and REF/INT

*3! SYNTAX ERROR ! The instrument did not understand the last command

Send correct command

*4! WRITE PROTECTED VALUE !

An attempt was made to change the CNint value

See Chapter 6 The Microprocessor System to remove the write protection

*5! INCORRECT CN-VALUE !

The value of CN EXT sent was < 10 pF or the old CN EXT value is not sensible

Enter the correct CN value

*6! 2818 IS NOT IN REMOTE STATE !

The instrument has received a software reset during remote operation (e.g. from a flashover)

Re-initialize the interface (CLEAR...) and restart remote control

*7! GROUND IS OFF ! An attempt was made to switch the high voltage on (VON) but there is no earth connection

Mains earth AND HV GND must be at earth

*8! SAFETY SWITCH IS OPEN !

The VON command was sent, but the safety switch is open

Depress the safety switch

*9! HIGH VOLTAGE IS OFF !

The VUP command or VDN command was sent, but the high voltage is not yet switched on

Check the test setup and switch the high voltage on (VON)




Message Cause Help

*10! TEST-OBJECT IS INDUCTIVE !

The test object capacitance was queried, (?CX), but the test object is an inductance

Query inductance (?LX)

*11! TEST-OBJECT IS CAPACITIVE !

The test object inductance was queried (?LX), but the test object is a capacitance

Query capacitance (?CX)

*12! TEST-VOLTAGE TOO LOW !

The test voltage (high voltage) is too low to achieve an accurate test result

Raise the test voltage

*13! AVERAGING IS NOT ACTIVE !

The average value was queried (?AA or ?AC), but averaging is not activated

Activate averaging (SAC)

*14! NOT POSSIBLE WITH REFERENCE EXTERNAL

Interference suppression can only be activated if internal reference is selected

Select REF-INTERNAL (CRI)

*15! TOO HIGH INTER- FERENCE

Extreme interference being experienced or interference suppression is defective

• Move the test system to a location where less interference is expected (e.g. in a laboratory)

• Replace the BOOSTER board

*16! INTERFERENCE SUPPRESSION IS NOT ACTIVE

Fine balance or saving settings is only possible after coarse balance and at least on measurement

Activate with SSG

*17! FIRST MEMORIZE THE SETTINGS

The internal settings must be saved before fine balance

Activate with SSM

*18! WORKING ON

SUPPRESSION

The interference suppression balance is in progress

Wait until the interference suppression has finished balancing or quit the balance with the command SSQ

*19! DURING HQ-MODE ONLY HQC ALLOWED

The interference suppression is already active and the process must be allowed to complete or interrupted with the HQC command.

Send the HQC command to interrupt the interference suppression process



Operation Manual

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Message Cause help

*20! HQ-MODE CANCELLED BY RELEASING SAFETY SWITCH

The HQ interference suppression process was interrupted as the safety switch was not depressed.

Keep the Safety Switch depressed during the entire interference suppression procedure

*21! NO OR OLD CONTROL-UNIT, HQ-MODE NOT POSSIBLE

The control unit of the 5383 high voltage supply is too old or not available.

Contact the factory regarding extension possibilities of your test system

*22! HQ-MODE ALREADY ACTIVE AND BUSY

HQ interference suppression was started when it was already active.

*23! TOO MANY CYCLES

The value entered for averaging lies outside the limits.

Enter a value between 0 and 99.

*24 ONLY AVAILABLE WITH TETTEX TYPE 2818

The command entered is only available in conjunction with the 2818 measuring bridge.

See the commands marked with a star * in Chapter 17.7 Command Set.




17.9. The RS-232 Interfaces

The measuring bridge is equipped with two built-in RS-232 interfaces as standard. One RS-232 interface is used as the printer interface and the second is used for remote control using a computer, whereupon the interface is converted to a GPIB socket using a special adapter cable.

As an option, the measuring bridge can be fitted with an IEEE-488 interface for remote control instead of an RS-232. It must be considered, regarding the RS-232 interface, that both types of interface cannot be built-in at the same time.

17.9.1. Communications Parameters

The communications parameters are identical for both of the RS-232 interfaces.

2400 Baud 8 Data bits No Parity

17.9.2. Interface and Technical Data

The interface (Bu 12) consists of a 25 pole standard socket (male). In order to avoid earth loops, there is no galvanic connection to the rest of the instrument as the data signal is fed via an opto-coupler.

17.9.2.1. Bu 12 pin-out: RS-232 interface (printer) Pin Signal name

1 Protective earth (from printer) 2 TxD (data output to printer) 3, 4, 5, 6 Not used 7 Signal earth 18 + 5V DC 8 ... 25 Not used

17.9.2.2. Bu 12 pin-out: RS-232 interface (computer) Pin Signal name

1 Protective earth 2 TxD 3 RxD 3, 4, 5, 6 Not used 7 Signal earth 18 + 5V DC 8 ... 25 Not used



Operation Manual

Page 119

17.10. PRINTER Wiring and Pin-out

Figure 46: Pin-out of printer socket (male) on the instrument rear panel

PIN SIGNAL SIGNAL FUNCTION

1 SCR Screen Shield

2 TxD Transmit Data Send line

3 Not used

4 Not used

5 Not used

6 Not used

7 GND Ground Signal earth

8 Not used

9 Not used

10 Not used

11 Not used

12 Not used

13 Not used

14 Not used

15 Not used

16 Not used

17 Not used

18 +5V +5V Supply for external opto-coupler

19 Not used

20 Not used

21 Not used

22 Not used

23 Not used

24 Not used

25 Not used

13121110987654321

252423222120191817161514




17.10.1. RS-232 Computer Interface

The measuring bridge is equipped as standard with an RS232 interface for remote control. However the connection is made via the INTERFACE IEEE 488 socket. A special adapter cable is supplied as standard (Nr. 020219-00 IEEE 488 / RS232). This adapter cable consists of a GPIB socket at one end and a 25-pole RS232 socket at the other.

The connector on the back of the measurement bridge is always a IEEE-connector independent of the interface (RS232 or IEEE 488) equipped. If the measurement bridge is equipped with a RS232 interface the RS232 cable must be connected to the adapter cable which is connected to the INTERFACE IEEE 488 socket at the bridge.

If the bridge is equipped with an IEEE 488 interface a standard IEEE cable is required for the connection between computer and bridge. Then the also connector INTERFACE IEEE 488 has to be used.

For remote control an RS232 interface cable is required, which must be wired as follows:

Figure 47: RS232 interface wiring measuring bridge - computer

RS 232 Cable

Computer

COM

123456789

Type 2816

Sockets / BuchsenPins / Sifte

RS 232 Kabel

DCDRxDTxDDTRGNDDSRRTSCTSRI

2818

12345678910111213141516171819202122232425

123456789101112131415161718192021222324

RS 232

Adapter cableRS 232 to IEEE

IEEE 488 ConnectorIEEE 488 Stecker

RS 232 connectorRS 232 Stecker

RS 232 connectorRS 232 Stecker



Operation Manual

Page 121

17.11. IEEE 488 Interface

Figure 48: Pin-out of GPIB socket on instrument rear panel

PIN SIGNAL SIGNAL FUNCTION

1 DIO1 Data Input/Output 1 Data line 1




5 EOI End Or Identify End or identification

6 DAV Data Valid Data valid

7 NRFD Not Ready For Data Not ready to receive

8 NDAC No Data Accepted Not accepted

9 IFC Interface Clear Interface system reset

10 SRQ Service Request Call for service

11 ATN Attention Warning

12 Shield Shield Screen





17 REN Remote Enable Released for operation

18 GND Ground Earth

19 GND Ground Earth

20 GND Ground Earth

21 GND Ground Earth

22 GND Ground Earth

23 GND Ground Earth

24 GND Ground Earth

12

24

11

23

10

22

9

21

8

20

7

19

6

18

5

17

4

16

3

15

2

14

1

13




Bridge 2816, 2818 Appendix C: Troubleshooting


Operation Manual

Page 123

18. Appendix C: Troubleshooting

If errors or faulty operation occur, then please report this with the firmware version number. Apparent problems can often be resolved by studying the operating instructions. It may also be possible that a newer firmware version is already available and instrument upgrades should always be under consideration.

18.1. Error Messages on the Display

Nr. Error message Possible causes Help

1 SORRY! TOO HIGH INTERFERENCE

Extreme interference conditions that can no longer be compensated for, or defective interference suppression.

• Move the test system to a location where less interference is expected (e.g. in a laboratory)

• Replace the DACO board

2 IMPOSSIBLE WHILE NOT MEASURING

The interference suppression fine balance was started but there are no measurement values available

• Perform a measurement by switching on the high voltage (HV ON) and pressing the RUN key.

3 IMPOSSIBLE INPUT TRY AGAIN

Date and / or time input incorrect • Enter the correct date and time

4 PROTECTED VALUE Attempted to change CN INT value when write protection was active

• Remove write protection (see Chapter 6.2)

5 YOUR INPUT VALUE IS OUT OF RANGE

Entered value of CN EXT is <10 pF or

CN INT is <90 pF or >110 pF or a temperature was entered for which there is no correction factor

• Use a CN EXT > 10 pF and enter the value.

• CN int must be 100 pF ± 10 pF otherwise call service

6 SORRY! THERE IS NO INPUT SIGNAL

REF EXT was selected but no high voltage is applied

• Check the test circuit and switch on the high voltage

7 THERE ARE NO VALUES TO PRINT

The PRINT key was pressed before a measurement was performed

• Perform a measurement

8 PRINTER IS STILL BUSY The PRINT key was pressed while the printer was already printing

• Wait until the printer has finished printing before pressing the PRINT key

9 PLEASE: RED KEY! TRY AGAIN!

No red key was chosen for TEST MODE • Press a red key to select the TEST MODE

10 WRONG! TRY A BLUE KEY!

No blue key was chosen for DISP MODE

• Press a blue key to select the DISP MODE

11 PLEASE REPROTECT MY MEMORY

Write protection is inactive • Re-enable the write protection (see Chapter 6 The Microprocessor System

Appendix C: Troubleshooting Bridge 2816, 2818



Nr. Error message Possible causes Help

12 THERE ARE NO MORE OIL TABLES

A non-existent oil table was selected • Only select a conversion table which has already been entered

13 NO FREE MEMORY FIRST DELETE ONE

An attempt was made to enter an eighth conversion table

• Only seven tables are possible. A table must be deleted.

14 SORRY, I HAVE A DAMAGE

IC XX ON I SGERF IS DEAD

The DATA READY signal of the A/D converter is missing

• If switching off and on again with the POWER button (= general reset) doesn’t help , then call service (probably the SIGERF card is faulty).

15 FREQUENCY TOO HI ERROR CODE 44

or

FREQUENCY TOO LOW ERROR CODE 89

The PLL for system synchronization is not functioning or not functioning correctly.

Measurement frequency > 65 Hz or < 30 Hz

Switched to REF EXT but the high voltage is missing

• Check the test circuit and switch on the high voltage or switch to REF INT. If not OK then call service.

16 SORRY, I LOST A PART OF MEMORY

Important data are no longer available for the microprocessor

• Re-enter the most important data such as CN EXT, TEST MODE, DISP MODE, USER SETUP etc.

17 CONSTANT-MEMORY SUPPLY IS EMPTY

NEED URGENT SERVICE

The non-volatile memory (NVRAM) battery has run out.

• After each switch-on the system parameters and, if required, conversion tables must be re-entered, in order to be able to perform measurements without the battery.

→ Order a new battery from Tettex (type. Nr. 7-017557-00-0)

18.2. Hardware Errors during the Measurement

Occurring error Cause / possible solution

Measurement of a negative dissipation factor tan δ

The standard capacitor connected to the CN socket has a worse dissipation factor than the test object connected to the CX socket:

• Check that the standard capacitor and test object are properly connected to the correct sockets.

• Check the standard capacitor. It could be defective.

• Large stray capacitance of the test object to the screen. Check the screening of the test object.

Measurement values are displayed, although nothing is connected to the instrument or no test voltage has been applied.

The instrument is probably running in demo mode with simulated measurement values:

Switch the instrument off and on again to restart the internal microcomputer.

The instrument will not start up, although the 30-second initialization time has passed.

• Is the mains cable connected?

• Check the built-in fuses.

Bridge 2816, 2818 Schematic Diagram


Operation Manual

Page 125

19. Schematic Diagram

Figure 49: Block schematic diagram of the entire measurement system

Schematic Diagram Bridge 2816, 2818



Bridge 2816, 2818 Instrument Photographs


Operation Manual

Page 127

20. Instrument Photographs

20.1. Views of the Type 2816 Measuring Bridge and Accessories

Figure 50: Photo of 2816; front view

Figure 51: Photo of 2816; rear view

Instrument Photographs Bridge 2816, 2818



Figure 52: Complete 3 part measuring system 2816/5284U consisting of measuring bridge, control unit and high voltage supply 12kV / 200mA



Operation Manual

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20.2. Views of the Type 2816/5284 Measuring Bridge and Accessories

Figure 53: Complete 2 part measuring system 2816/5284 consisting of measuring bridge, control unit with high voltage supply 12kV / 200mA




Figure 54: Photo of 5284 control unit, front view

Figure 55: Power supply type 5284, Connection part



Operation Manual

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20.3. Views of the Type 2818 Measuring Bridge and Accessories

Figure 56: Photo of 2818, front view

Figure 57: Photo of 2818, rear view




Figure 58: Complete 3 part measuring system 2818/5283 consisting of measuring bridge, control unit and high voltage supply 12kV / 200mA

Bridge 2816, 2818 Catalogue of Literature


Operation Manual

Page 133

21. Catalogue of Literature

[1] IEC 289 Reactors

[2] IEC 76-3-1 (1987) Power transformers, Part 3: Insulation levels and dielectric tests, External clearances in air.

[3] ANSI/IEEE C57.12.90-1993 American National Standard test code for liquid-immersed distribution power, and regulating transformers and guide for short-circuit testing of distribution and power transformers

[4] Die Prüfung von Leistungstransformatoren. 1983 Buchverlag «Elektrotechnik», Walter Liechti. Autoren: D. J. Kraaij / G. S. Schemel / F. M. Wegschneider

[5] Tettex Applikation TA 509, Dielektrische Messungen (C tan δ) an rotierenden Maschinen (TA 509d - 10-2.91).

[6] Tettex Information No. 26: „Dielectric Measurement of high - voltage apparatus in the interference field of a substation“ von K. Fischer

[7] Tettex Information No. 22: „Accuracy of capacitance and dissipation factor tan δ measuring bridges“

[8] Tettex Applikation TA 515, Dielektrische Messungen (C / tan δ) an elektrischen Hochspannungsapparaten mit dem automatischen Isolationsprüfsystem Type 2818/5283 (TA 515d - 15-3.92 - Nr. 095015-D0-0.D).

[9] Tettex Procedure 0015, Feldmessung von Kurzschlussimpedanzen an Leistungstransformatoren

Catalogue of Literature Bridge 2816, 2818



Bridge 2816, 2818 Index


Operation Manual

Page 135

22. Index

A accessories and options ...................................................99 accuracy conditions...........................................................4 accuracy considerations with comparator........................79 ANSI/IEEE standard C57.12.90 -1993 ...........................53 averaging, enter number of measurement values, OPT 1 45

B battery for the non-volatile memory................................63 brief operation guide .......................................................84 bus structure IEEE 488 .................................................112

C C tan δ measurement ..................see functional description calibration .......................................................................89 capacitance measurement ...........see functional description capacitor

parallel equivalent circuit ...........................................20 series equivalent circuit ..............................................20 vector diagram of a real capacitance...........................11

coarse balance .................................................................41 comparator ....................................................47, 58, 76, 99 conditions for accuracy specifications...............................3 connections

high voltage................................................................26 interfaces ....................................................................28 mains connection........................................................25 measurement connections...........................................27 system earth HV ground.............................................27

conversion of tan δ referenced to 20°C ..........................52 conversion to 10kV, OPT 3.............................................46 current comparator ..............................................47, 58, 76

D data

general ..........................................................................5 mechanical....................................................................5 technical .......................................................................4

display.............................................................................31 capacitance / inductance.............................................31 dissipation factor / power factor .................................31 impedance Z, OPT 7...................................................49 test voltage / current ...................................................32

dissipation factor tan δ difference to cos ϕ ......................................................11 what is it? ...................................................................10

dot matrix display............................................................32 dynamic averaging, OPT 1..............................................45

E earth connection.............................................................. 27 earth connections ............................................................ 18 earth protection................................................................. 8 earth terminal.................................................................. 27 earthing........................................................................... 18 EPROM .......................................................................... 61 equivalent circuit ...................................................... 19, 48 equivalent circuit calculation, OPT 5 ............................. 48

F fine balance..................................................................... 42 firmware............................................................................ 1 functional description

C tan δ measurement.................................................. 20 dynamic averaging ..................................................... 24

fuse ................................................................................... 8

G general data.............................................................see data getting started ................................................................. 81 Getting Started................................................................ 81

H hardware ........................................................................... 1 high voltage bushings ................................................... 107 high voltage supply................................................. 15, 100

I IDENT INPUT ..................See measurement identification impedance Z, OPT 7....................................................... 49 inductance measurement......................................... 23, 105 insulation measurement

theory of....................................................................... 9 interface

IEEE .......................................................................... 28 printer ........................................................................ 29 RS232 ........................................................................ 28

interface command set .................................. 114, 115, 116 interfaces

IEEE address setting..................................................... 113 pin-out................................................................. 123

PRINTER pin-out................................................................. 121

interference suppression .. 41. See interference suppression High Quality Mode .................................................... 43

Index Bridge 2816, 2818



L literature ....................................................................... 135 location of the instrument............................................... 65 loss factor

what is it? .................................................................. 10

M mains connection............................................................ 25 mains plug ........................................................................ 8 mains power connection................................................. 17 mains supply connection .................................................. 6 maintenance.................................................................... 89 measurement connections............................................... 27 measurement identification IDENT INPUT ................... 37 measurement location entry, IDENT INPUT 4 .............. 40 measurement of capacitance ........................................... 20 measuring cable.............................................................. 16 mechanical data .....................................................See Data menu structure (brief operation guide) ........................... 84 microprocessor ........................................................... 1, 61 microprocessor system ................................................... 61

N numerical keys................................................................ 33

O object, IDENT INPUT 2 .......................................... 38, 40 oil factor tables ............................................................... 50 options OPT ................................................................... 45

P power

apparent power .......................................................... 12 reactive power ........................................................... 12 real power .................................................................. 12

power factor cos ϕ .......................................................... 11 precautions, safety............................................................ 7 printer ............................................................................. 54 printer selection → int. Printer, OPT 6 .......................... 49

R recycling......................................................................... 97 reference conditions ......................................................... 3 resonant suppy.............................................................. 100 revisions and corrections.............................................. 101

S safety ................................................................................ 7 saving the measurement values ..................... See RUN key scope of delivery ............................................................ 95 serial number, IDENT INPUT 1............................... 38, 40

service .............................................................................89 set time, IDENT INPUT 3 ..............................................39 SETUP............................................see start-up parameters software.............................................................................2 standard capacitor CN

determination of .........................................................19 what is a .....................................................................15

standard capacitor CN................................................36, 99 start-up parameters, SETUP OPT 2 ................................46 storage.............................................................................93 system earth

connection to..............................................................65 system parameters ...........................................................61 system reference EXT/INT .............................................37

T technical data ......................................................... see data temperature correction factors.........................................53 test cells ........................................................................100 test circuit .......................................................................65

dissipation factor measurements on single-phase shunt reactors ................................................................108

dissipation factor measurements on three-phase shunt reactors ................................................................109

inductance measurement according to IEC 76-5......105 machine with externally configurable winding system

............................................................................104 measurements on high voltage bushings ..................107 measurements on high voltage cables ......................106 measurements on transformer with tertiary winding ..67 measuring a single-phase autotransformer with tertirary

winding .................................................................72 measuring a transformer with two windings ..............73 measuring a Yn-∆ three-phase transformer ................75 measuring Yn-Yn three-phase transformers...............74 standard test circuit principle diagram .......................69 test current extension with external comparator.........78

test current maximum ...................................................................18

test mode.............................................................33, 66, 67 test object ........................................................................17 test report ........................................................................55 test report printing PRINT ..............................................54 test results

evaluation of ..............................................................13 test setup .........................................................................65 test voltage

maximum ...................................................................18 minimum....................................................................18

time entry, IDENT INPUT 3...........................................39 trouble shooting ..............................................................91 troubleshooting .............................................................125

V vectorvoltmeter principle ................................................20 voltage ........................................................see test voltage

Bridge 2816, 2818 Notes


Operation Manual

Page 137

23. Notes

Documents

Manual_2816-2818 Obratiti Paznju