RMO-TW - WINDING OHMMETERS Manual - ITM Instruments

RMO-TW WINDING OHMMETERS

Manual

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RMO-TW Contents

M-RXX0TW-201-U-EN 2

Contents

1. Introduction ............................................................................................................................................................. 3 1.1 Safety Instructions ............................................................................................................................................ 3

1.1.1 Safety Terms and Symbols ....................................................................................................................... 3 1.1.2 Terms of Use ............................................................................................................................................ 3 1.1.3 Orderly Practices and Procedures ............................................................................................................ 4 1.1.4 Device Maintenance ................................................................................................................................. 4 1.1.5 Operator Qualifications ............................................................................................................................. 4 1.1.6 Safe Operating Procedures ...................................................................................................................... 4

1.2 Power Supply .................................................................................................................................................... 5 1.3 Measurement Category .................................................................................................................................... 5 1.4 Intended Use ..................................................................................................................................................... 6

2 Description ............................................................................................................................................................... 7 2.1 Front and Rear Panel Components .................................................................................................................. 7

3 Testing .................................................................................................................................................................... 10 3.1 Connecting the RMO-TW to a Test Object ..................................................................................................... 10 3.2 The Current Test ............................................................................................................................................. 11

3.2.1 Setting the Measurement Parameters .................................................................................................... 11 3.2.2 The Measurement Process ..................................................................................................................... 11 3.2.3 Viewing the Test Results ........................................................................................................................ 13

3.3 The Tap Changer Test .................................................................................................................................... 13 3.3.1 Setting the Measurement Parameters .................................................................................................... 14 3.3.2 Tap Changer Test with the RMO-TW ..................................................................................................... 15

3.4 Measurement Parameters .............................................................................................................................. 17 4 Error Messages ...................................................................................................................................................... 18

4.1 Error Message "Open Connection" ................................................................................................................. 18 4.2 Error Messages "Connection CH1-2-3" and "Connection CH1" ..................................................................... 18 4.3 Error Message "Polarity" ................................................................................................................................. 19 4.4 Error Messages "Change Current" and “Overcurrent” .................................................................................... 19 4.5 Error Message "Overheat" .............................................................................................................................. 19 4.6 Error Message "Mains Voltage < 90V" ........................................................................................................... 20 4.7 Error Messages "Error Printer" and "Check Paper" ........................................................................................ 20

5 Troubleshooting ..................................................................................................................................................... 21 5.1 Accuracy Check .............................................................................................................................................. 21 5.2 Open Circuit Voltage Check ........................................................................................................................... 21 5.3 Test Currents Check ....................................................................................................................................... 22 5.4 Voltage Measurement Check ......................................................................................................................... 23 5.5 TestCom Diagnostic Software ........................................................................................................................ 23

6 Customer Service ................................................................................................................................................... 24 7. Packing the Instrument for Shipment ..................................................................................................................... 24 8 Technical Data ....................................................................................................................................................... 25

8.1 Mains Power Supply ....................................................................................................................................... 25 8.2 Output Data ..................................................................................................................................................... 25 8.3 Measurement .................................................................................................................................................. 25 8.4 Environmental Conditions ............................................................................................................................... 25 8.5 Dimensions and Weight .................................................................................................................................. 26 8.6 Applicable Standards ...................................................................................................................................... 26

9 Instrument & Accessories ...................................................................................................................................... 27 Manufacturer Contact Information .................................................................................................................................. 28

Manual Version: M-RXX0TW-201-U-EN

This Manual refers to the firmware version 11.00

Refers to:

RMO10TW, RMO20TW, RMO30TW and RMO50TW models


RMO-TW Introduction

M-RXX0TW-201-U-EN 3

1. Introduction

The purpose of this Manual is to provide helpful instructions on how to use the RMO-TW instruments safely,

properly and efficiently.

The following instructions will help the user avoid unsafe situations, reduce maintenance costs and will ensure

the reliability and durability of the RMO-TW instruments.

The RMO-TW must be used in observance of all existing safety requirements and regulations based on

national/local standards for accident prevention and environmental protection. In addition, the relevant

international standards are listed in paragraph 8.6 of the “Technical data” section of this document.

1.1 Safety Instructions

Safety is the responsibility of the user. Before operating the RMO-TW, please read the following safety

instructions carefully.

It is not recommended that the RMO-TW is used (or even turned on) without careful observation of the

instructions listed in this Manual. The RMO-TW should only be operated by trained and authorized personnel.

1.1.1 Safety Terms and Symbols

Terms in this Manual. The following terms may appear in this manual:

WARNING: Warning statements identify conditions or practices that could result in injury or loss of life.

CAUTION: Caution statements identify conditions or practices that could result in damage to this product or to

other property.

Terms on the Device. The following warning terms used in this document may appear on the device:

WARNING: indicates that potential hazard may occur.

CAUTION: indicates that potential damage may occur to the instrument or to the test object connected to the

instrument.

Symbols on the Product. The following symbols may appear on the device:

Refer to Protective

Manual Earth

Terminal

1.1.2 Terms of Use

• The RMO-TW shall be used only if it is in good technical condition. Its use shall be in accordance with

local safety and industrial regulations. Adequate precautions must be taken to avoid any risks related to

high voltages associated with this equipment and nearby objects.

• The RMO-TW shall be used only for the application purposes specified in the ”Intended Use” section of

this Manual. The manufacturer and distributors are not liable for any damage resulting from wrong

usage. The user bears responsibility in case of not following the instructions defined in this document.

• Do not remove the protective casing of the RMO-TW.

• All service and maintenance work must be performed by qualified personnel only.


RMO-TW Introduction

M-RXX0TW-201-U-EN 4

1.1.3 Orderly Practices and Procedures

• The Manual shall always be available on the site where the RMO-TW is used.

• Before using the RMO-TW, all personnel (even personnel who only occasionally, or less frequently,

work with the RMO-TW) assigned to operate the RMO-TW should read this Manual.

• Do not make any modifications, extensions, or adaptations to the RMO-TW.

• Use the RMO-TW only with the original accessories provided by its manufacturer.

• Use the RMO-TW and its original accessories for the device's intended use only.

1.1.4 Device Maintenance

This device should be kept clean in order to prevent excessive cases of dust or other contaminants affecting its

operation. It should be cleaned with water/isopropyl alcohol after any dirt/contaminants are noticed on its

surfaces.

1.1.5 Operator Qualifications • Testing with the RMO-TW should only be carried out by authorized and qualified personnel.

• Personnel receiving training, instruction or education on the RMO-TW should remain under the constant

supervision of an experienced operator while working with the test set and the test object.

1.1.6 Safe Operating Procedures

• Hazardous voltages of up to 400 V can occur inside the RMO-TW. Therefore, it is not permitted to remove

the protective casing of the RMO-TW.

• Hazardous voltages exist on the terminals of the RMO-TW when the red LED is lit. Never assume that the

connections are safe even if this LED is off. Switch off and unplug the RMO-TW before touching the

connections, particularly if a fault is suspected.

• Before putting the RMO-TW into operation, check the test set for any visible damage.

• Cables between the RMO-TW and other equipment shall be connected and disconnected from the RMO-

TW only while the instrument is switched off.

• Do not operate the RMO-TW under wet or moist conditions (condensation).

• Do not operate the RMO-TW if explosive gas or vapors are present.

• Only the external devices which meet the requirements for SELV equipment according to EN 60950 or IEC

60950 should be connected to the RMO-TW through the serial interface.

• When setting up the RMO-TW, make sure that the air slots of the test set remain unobstructed

• Removing the RMO-TW protective casing by unauthorized persons will void the warranty. Any work inside

the instrument without prior authorization by DV Power will also void the warranty.

• If the RMO-TW seems to be malfunctioning, please contact the DV Power Support Team (refer to the

"Manufacturer Contact Information” section) after previously checking the “Error Messages” section.

• Prior to connecting the RMO-TW, ensure that the transformer (object) to be tested is completely de-

energized and isolated from both the line and the load. Every terminal should be checked and verified

before connecting the RMO-TW. Ground connections may be left in place.

• Do not use the RMO-TW without the extra protective ground cables supplied with the RMO-TW. It must

never be operated in a non-grounded configuration as this may result in an electric shock to the user or


RMO-TW Introduction

M-RXX0TW-201-U-EN 5

damage to the RMO-TW. Always establish this connection as the first step before establishing any other

connections, and remove this connection last.

• Wherever possible, the outer casing of the transformer under test should also be connected to a safety

earth to prevent the risk of shock. Where this cannot be achieved, adequate precautions should be taken

to prevent access to the transformer (e.g. barriers).

Never open the measuring circuit while the test is in progress as dangerous high voltage may

occur.

Never change the De-Energized Tap Changer (DETC) position while the test is in progress.

This can cause excessive voltage arcs within the transformer and on external terminals.

1.2 Power Supply

• Supply the RMO-TW only from a power outlet which is equipped with protective ground.

• Besides supplying the RMO-TW from phase-neutral (L1-N, A-N), it may also be supplied from phase to

phase (e.g., L1-L2; A-B). However, the voltage must not exceed 264 V AC. Please refer to the “Technical

Data” section.

The RMO-TW should be positioned in such a way that it is possible to safely disconnect it from the power

supply at any moment.

WARNING / AVERTISSEMENT

This is a class A product. In a domestic environment this product may cause radio interference in which

case the user may be required to take adequate measures.

Il s'agit d'un produit de classe A. Dans un environnement domestique, ce produit peut provoquer des

interferences radio, auquel cas l'utilisateur peut être amené à prendre des measures adéquates.

1.3 Measurement Category

The RMO-TW is intended to be used for measurements in Measurement Category I (CAT I) for voltages up to

300V. The device is also designed to withstand occasional transient overvoltage of up to 1000Vpk.

WARNING / AVERTISSEMENT

This equipment is classified as measurement category I and must not be used within measurement

category II, III and IV.

Cet équipement est classé dans la I catégorie de mesure, et ne doit pas être utilisé pendant les

catégories de mesure II, III et IV.


RMO-TW Introduction

M-RXX0TW-201-U-EN 6

1.4 Intended Use

The Winding Ohmmeter RMO-TW is a stand-alone or PC-controlled digital instrument designed for detailed

analysis of on-load tap changers and for measuring resistances of inductive test objects used in the electric

power industry or similar industries. It is employed for resistance measurement during the manufacturing,

commissioning and testing of:

transformers,

on-load tap changers,

de-energized tap changers,

generators and electrical motors,

high current busbar joints,

cable splices.

The RMO-TW is also used to create the automatic resistance/temperature measurement for the Heat Run test

together with the DV-Win software.

Any uses of the RMO-TW other than the ones mentioned above are considered improper and will invalidate

warranty claims.


RMO-TW Description

M-RXX0TW-201-U-EN 7

2 Description

2.1 Front and Rear Panel Components

1. Operator Control

Display

Displays the settings during the device test mode selection as well as the measured values during and

after a test operation.

Keyboard

Used to control the device.

• UP/DOWN buttons are used to navigate and set the test parameters.

• ENTER confirms the defined test parameters, language, time and date, and also navigates through

menus. During the test it is used to switch to the measurement of the next phase.

• STOP stops the test, interrupts the alarm buzzer and to return to the previous menu.

• Ω records the resistance value currently displayed on the screen in the RMO-TW instrument internal

memory

• START starts the test.

• SET scrolls between the Current, TapC and Memory menus.

Green LED

• Lights continuously when the RMO-TW is turned on.

• Flashes when the test can be started.

• Flashes alternately with the red LED during the Current and TapC test.

Figure 2-1:

Front panel of the instrument


RMO-TW Description

M-RXX0TW-201-U-EN 8

Red LED

• Lights continuously in case of operational error.

• Lights continuously during a discharging process.

• Flashes alternately with the green LED during the Current and TapC test.

• Flashes shortly during a resistance measurement in the TapC test.

2. USB PC Interface

The USB PC interface enables controlling the instrument from a PC and downloading previously recorded

results from the instrument’s internal memory. A USB cable is provided as an accessory.

3. Discharge LED

The red LED remains lit until the accumulated energy of the measured object is reduced to a harmless

level.

CAUTION

While the discharge LED is lit, the measurement cables must not be disconnected.

CAUTION

While disconnecting cables, do not bridge the circuit with your body parts!

In case of shorting a winding for the DRM test, it should be noted that a very small current may remain

flowing through the shorted winding even when the discharging process has finished. For that reason

a person should use only a single hand when disconnecting the shorting cable, to avoid the other hand

creating a return path if touching a transformer. For maximum safety insulating gloves should also be

used.

4. Voltage sense cables terminals

Terminals for connecting up to two pairs of voltage sense cables.

5. Current cables terminals

Terminals for connecting “+ / red” and “- / black” test current cables.

6. Mains Power Connector

Connects the RMO-TW to the mains power supply with a power cord.

Figure 2-2:

Rear panel of the instrument


RMO-TW Description

M-RXX0TW-201-U-EN 9

7. Power Switch

Power switch – Double pole switch

I - In this position, the RMO-TW is connected to the mains power supply.

0 - In this position, the RMO-TW is separated from the mains power supply.

8. Protective Earth Connector

For protection against parasitic currents or voltages, the RMO-TW earth/ground connector should always

be connected to protective ground (PE). Only the originally provided cable should be used for this purpose.

For safety reasons, this connection should be established as the first one before any other

connections and removed last.


RMO-TW Testing

M-RXX0TW-201-U-EN 10

3 Testing

3.1 Connecting the RMO-TW to a Test Object

Before the RMO-TW has been connected to a test object (e.g. a power transformer), the following steps have

to be taken:

• The test object needs to be disconnected from its circuit in accordance to the national safety regulations

and properly grounded to protective earth.

• The transformer needs to be completely de-energized.

• The RMO-TW itself needs to be properly grounded. To do so, the grounding screw should be connected

to protective earth using the original grounding cable.

• One end of the measured windings needs to be properly grounded. The only exception is in the case of

the YN connection being tested and neutral and earth bonds are mutually connected. In this case, one

side of the measurement circuit should not be earthed because it is not necessary and because it will

incorrectly affect the RMO-TW reading.

Note: Always connect measuring cables to the RMO-TW instrument first and then to the test

object. When disconnecting, always disconnect the cables from the test object first and then

from the RMO-TW.

The grounding wire PE should be disconnected last.

Not following these instructions may cause life-threatening situations.

Figure 3-1: Connecting a test object to the RMO-TW

With the RMO-TW turned off, the RMO-TW needs to be connected to the test object in such a way that the

measuring cables from the "Voltage Sense" sockets are attached as close as possible to the winding and in

between the current feeding cables. That way, the resistance of cables and clamps is almost completely

excluded from the resistance measurement. When connecting the measuring cables, attention should be

paid to polarity.


RMO-TW Testing


To maximize the accuracy and measurement repeatability, all clamps need to have a good connection to the

test object.

CAUTION

For safety reasons, a connection of the device should be always established with the test object in

the way described in this Manual.

The measuring cables should not be connected after the start of the test.

The leads should not be disconnected before the discharge LED and the alarm buzzer are off.

The RMO-TW instrument can perform the following tests:

- Current test

- Tap Changer test.

3.2 The Current Test

3.2.1 Setting the Measurement Parameters

After the initial display, the RMO-TW automatically changes to the Current menu and the green LED lights

up.

3.2.2 The Measurement Process

To start the measuring sequence, the following values need to be selected:

Test current. The following values can be chosen: 5 mA, 10 mA, 50 mA, 100 mA, 500 mA, 1 A, 2 A, 5

A, 10 A, 15 A(*), 20 A(*), 25 A(**), 30 A(**), 40 A(***) and 50 A(***).

* available with the RMO20TW, RMO30TW and RMO50TW models

** available with the RMO30TW and RMO50TW models

*** available with the RMO50TW model

Memory position. This parameter sets the memory position in which the first measurement results will

be saved. Once the test is completed (either due to time expiration or when pressing STOP), the last

measured result will remain registered in the RMO-TW and the memory position is automatically

switched over to the next memory position. The result can be recalled later by selecting that position

number. Positions 000 - 499 can be selected.

Figure 3-2: The Current

menu

Test current

Test duration time

Menu name

Memory

Time and Date


RMO-TW Testing


Test duration time. The following values can be selected: 30 s, 60 s, 90 s, 2 min, 3 min, 4 min, 5 min,

6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 30 min, 60 min, 90 min,

unlimited.

The available values are selected by pressing UP/DOWN. The next parameter is selected by pressing RIGHT.

Once the information has been confirmed by pressing ENTER, the Ready screen will be displayed.

The Ready state displays the selected test current and its defined duration. If one of these values needs to be

changed, press STOP to return to the Current menu.

The flashing green LED indicates that the RMO-TW is now ready to start the test. Pressing START will

run the test. At the start of the test, a cable connection check is done. If an open circuit is detected, the

alarm will be activated and the appropriate error message will be shown on the display.

During the test, both the green and the red LEDs flash alternately. When the current is stabilized, the

RMO-TW starts the measurement of the test object resistance.

The following values are displayed during the test: test current, currently measured resistance values, time

remaining until the end of the test procedure and the active memory position. Two resistance values can be

measured simultaneously.

During the test, it is necessary to wait for the test current stabilization in order to obtain reliable results. The

current stabilization can be tracked by observing the Delta R value on the right side of the screen, or by

observing the resistance values themselves. The Delta R information provided is the deviation of the resistance

Δ which can be used to track the current stabilization process. The closer the Δ is to 0%, the results are more

stable. These values are automatically refreshed every second.

Note: The Current menu is not intended for on-load tap changer testing and the tap changer should not be

operated while testing in this mode. The TapC menu should always be used for tap changer analysis instead.

Pressing Ω will save the measured resistance results in the internal memory of the RMO-TW, and the memory

position is automatically switched over to the next memory position. These results can be recalled later by

selecting that position number.

Figure 3-3: The Ready screen

Figure 3-4: The Charging screen

Figure 3-5: The Current

menu during the test


RMO-TW Testing


The test can be completed in two ways:

- By pressing STOP,

- Automatically, after the selected time has expired.

When the test is finished either because the selected time has expired or the STOP button has been

pressed, the RMO-TW switches to the Results menu and starts the discharging process. During the

discharging, the discharge LED lights and the alarm beeps.

Discharge is completed when the discharge LED and the buzzer are OFF. Also, during that period the

“Discharging” message is shown on the display. During the discharging process it is not possible to start

another measurement.

When the test is stopped, the RMO-TW immediately stops producing output voltage. However, because of the

test object inductivity, the current still flows. Because of the enormous amount of energy that can be stored in a

magnetic field, precautions should be taken before disconnecting the test leads from the tested transformer.

Never remove the leads during the testing process and always allow enough time for the tested transformer to

completely discharge. Large transformers can require several minutes to discharge.

C A U T I O N

DO NOT DISCONNECT LEADS BEFORE THE “DISCHARGING” MESSAGE DISAPPEARS FROM THE

DISPLAY AND THE DISCHARGE LED IS OFF.

A T T E N T I O N

NE PAS DÉBRANCHER LES CONDUCTEURS AVANT QUE LE MESSAGE

''DÉCHARGER/DISCHARGING'' EST DISPARU DE L'ÉCRAN ET QUE LA DIODE DE DÉCHARGE EST

ÉTEINTE.

3.2.3 Viewing the Test Results

Once the test is finished, the RMO-TW automatically changes to the Results menu to display the test results.

3.3 The Tap Changer Test The winding resistance of individual taps of a power transformer’s tap changer can be measured by using the

Tap Changer (TapC) mode of the RMO-TW. There is no need to charge and discharge the transformer

between tap position changes. The inputs of the instrument are protected during the switching process in order

to avoid damage to the instrument in case of a faulty tap changer.

The RMO-TW injects a constant current into the power transformer. The winding resistance is calculated from

this current value and the measured voltage value. An interruption caused by a defective tap changer results in

comparatively high measured values of the current ripple.

Figure 3-6: The Results menu

showing the test results


RMO-TW Testing


3.3.1 Setting the Measurement Parameters

Turn on the RMO-TW with the power switch on the back of the test set. The display shows the

Current menu and the green LED lights up. Press SET to go to the TapC menu.

In the TapC menu, the following values need to be defined:

• Test current. The following values can be selected: 1 A, 2 A, 5 A, 10 A, 15 A(*), 20 A(*).

* available with the RMO20TW, RMO30TW and RMO50TW models

• Memory position. This parameter sets the memory position in which the first measurement results will

be saved. Once the test is completed, the last measured result will remain saved in the RMO-TW, and

the memory position is automatically switched over to the next memory position. The result can be

recalled later by selecting that position number. Positions 000 - 499 can be selected.

The available values are selected by pressing UP/DOWN. The next parameter is selected by pressing RIGHT.

Once the information has been confirmed by pressing ENTER, the Ready screen will be displayed.

The Ready state displays the selected test current and memory location. If one of these values has to be

changed, press STOP to return to the TapC menu.

Note: Only CH1 (the upper channel) is active during the TapC measurement.

Figure 3-7: Connecting a test object to the RMO-TW

Figure 3-8: The TapC

menu

Test current

Memory position

Menu name

Active channel

Figure 3-9:

The Ready screen

Time and Date


RMO-TW Testing


3.3.2 Tap Changer Test with the RMO-TW

The flashing green LED indicates that the RMO-TW is now ready to start the test. Press START to run a

test. At the start of the test, a cable connection check is done. If an open circuit is detected, the alarm is

activated and the error message is shown on the display

During the period of current stabilization, both the green and the red LEDs flash alternately and the

message “PLEASE WAIT CHARGING” is shown on the display.

The following values are displayed during this part of the test: the test current, the effective value of the

measured resistance, and the active memory position. The current stabilization can be tracked by observing

the Delta R value on the right side of the screen, or by observing the resistance values themselves. These

values are automatically refreshed every second.

At the moment the resistance result is stable, the resistance value of the on-load tap changer starting position

can be saved by pressing Ω. The memory position is automatically switched over to the next one and the

device is ready to record the current ripple.

While the resistance value is being saved, the red LED flashes shortly and the beeper sounds in higher

speed intervals.

The RMO-TW detects the change of the test current during the tap position change and measures the

difference between the starting current and the lowest value it reaches during the transition. This value is called

the transition ripple, and it is indicated as a percentage of the starting current value.

The display shows the test current value in the new tap position (here 9.82 A), and the value of the current

ripple which occurred during the change from the previous position to the new one (here 4.7 %). The current

stabilization can be followed on the display. After it has been stabilized, the RMO-TW shows the resistance

Figure 3-12: The TapC menu,

memory location is increased by one

Figure 3-10: The TapC

menu when the test current is stabilized

Figure 3-11: The TapC menu,

“Change tap position” message


RMO-TW Testing


value in the new tap position (here 576.4 mΩ). Pressing Ω will save the resistance and the ripple in the new tap

changer position.

This procedure is repeated until the ripples and resistance values are obtained for all the tap changer positions.

The tap changer test is completed by pressing STOP. The transformer is then automatically discharged.

During the current discharging process, the discharge LED lights and the alarms beep. Discharge is

completed when the discharge LED and the buzzer are OFF. It is not possible to start another

measurement during this process.

C A U T I O N

DO NOT DISCONNECT LEADS BEFORE THE “DISCHARGING” MESSAGE DISAPPEARS FROM

THE DISPLAY AND THE DISCHARGE LED AND BUZZER ARE OFF.

A properly working tap changer differs from a malfunctioning one by the magnitude of the current ripple value.

An open circuit during the transition will result in a much higher current ripple value (99 % or 100 %) than a

properly functioning tap changer.

Note: The current ripple value depends on the construction of the tap changer. It is recommended to compare

current ripple values to the values of other tap transitions in the same measurement. It is also recommended to

compare the current ripple results with the reference results from a previous tap changer test on the same

transformer.

The figure below shows an indication of possible tap changer discontinuity during the tap position change from

one tap position to the next one.

If the current circuit is interrupted during the tap position change, the „Discontinuity“ message will be shown on

the display, the red LED will light and the buzzer will beep continuously. The discharging process will be

initiated.

Figure 3-13: The TapC menu during

discharging

Figure 3-14: The TapC menu

showing a much higher current ripple value

Figure 3-15: The "Discontinuity" message


RMO-TW Testing


3.4 Measurement Parameters

The highest resolution of the reading is always displayed. The resistance range selection is performed

automatically and therefore manual setting by the operator is not necessary.

Table 3.1: Maximum resistances for each test current

Test

Current

Max Test

Voltage

RMO10TW

Max Test

Voltage

RMO20TW

Max Test

Voltage

RMO30TW

Max Test

Voltage

RMO50TW

Max

Resistance

RMO10TW

Max

Resistance

RMO20TW

Max

Resistance

RMO30TW

Max

Resistance

RMO50TW

5 mA 50 V 50 V 50 V 50 V 10 kΩ 10 kΩ 10 kΩ 10 kΩ

10 mA 50 V 50 V 50 V 50 V 5 kΩ 5 kΩ 5 kΩ 5 kΩ

50 mA 50 V 50 V 50 V 50 V 1 kΩ 1 kΩ 1 kΩ 1 kΩ

100 mA 50 V 50 V 50 V 50 V 500 Ω 500 Ω 500 Ω 500 Ω

500 mA 50 V 50 V 50 V 50 V 100 Ω 100 Ω 100 Ω 100 Ω

1 A 50 V 50 V 50 V 50 V 50 Ω 50 Ω 50 Ω 50 Ω

2 A 50 V 50 V 50 V 50 V 25 Ω 25 Ω 25 Ω 25 Ω

5 A 50 V 50 V 50 V 50 V 10 Ω 10 Ω 10 Ω 10 Ω

10 A 50 V 50 V 50 V 50 V 5 Ω 5 Ω 5 Ω 5 Ω

15 A - 50 V 50 V 50 V - 3.33 Ω 3.33 Ω 3.33 Ω

20 A - 37,5 V 42.5 V 50 V - 1.87 Ω 2.125 Ω 2.5 Ω

25 A - - 34 V 40 V - - 1.36 Ω 1.6 Ω

30 A - - 28.33 V 33.3 V - - 944 mΩ 1.11 Ω 40 A - - - 25 V - - - 625 mΩ

50 A - - - 20 V - - - 400 mΩ

Table 3.2: Resolution and full scale for each measuring range

Full scale Resolution

0.1 μΩ – 999.9 μΩ 0.1 μΩ

1.000 mΩ – 9.999 mΩ 1 μΩ

10.00 mΩ – 99.99 mΩ 10 μΩ

100.0 mΩ – 999.9 mΩ 0.1 mΩ

1.000 Ω – 9.999 Ω 1 mΩ

10,00 Ω – 99.99 Ω 10 mΩ

100.0 Ω – 999.9 Ω 0.1 Ω

1.000 kΩ – 9.999 kΩ 1 Ω

Typical accuracy of the RMO-TW instruments is ±(0.1% rdg + 0.1% F.S) for 0.1 μΩ – 1.999 kΩ range, and

±(0.2% rdg + 0.1% F.S) for 2.000 kΩ – 9.999 kΩ range. These accuracies are valid if the maximum possible

current is used. As high current as possible should always be selected, but to avoid the risk of heating the

winding, it is recommended not to exceed from 10 % to 15 % of the transformer nominal current. It is important

to make a good connection between the clamps and the connecting points on the test object to achieve stable

and accurate test results.

The guaranteed accuracy of the RMO-TW instruments is ± (0.2 % rdg + 0.2 % F.S).


RMO-TW Error Messages


4 Error Messages

Any operational error is indicated by a red LED and accompanied by an alarm. Furthermore, the display

indicates an error status message. To stop the alarm buzzer and return to the test menu, the status message

should be removed from the display by pressing STOP.

4.1 Error Message "Open Connection"

The Error message "Open Connection" is displayed if the current path is interrupted.

Figure 4-1: An example of interruption of the current path – a current cable disconnection

4.2 Error Messages "Connection CH1-2-3" and "Connection CH1"

The Error message "Connection CH1-2-3" is displayed if channel 1and channel 2 are all disconnected. This

message is displayed if either + or – voltage sense cable or both are disconnected either on the device side or

on the side of the test object.

The Error message "Connection CH1" is displayed only if CH1 is not connected during the tap changer testing.

This message is displayed if either + or – voltage sense cable or both are disconnected either on the device

side or the side of the test object.

These messages can be displayed only at the beginning of the test.

Figure 4-2: Error message "Open Connection"

Figure 4-3: Error message "Connection"




4.3 Error Message "Polarity"

The Error message "Polarity" is displayed if the voltage sense cables are connected with opposite polarity

either on the side of a device or the side of a test object, and the measured voltage signal is higher than 60

mV. Unlike other error messages, the test will not be interrupted. A “Polarity” warning will be displayed as

shown on the figure below.

Note: Since 60 mV is the signal threshold, the display will show the result with lower accuracy for lower voltage

signal values. If some of the cables are disconnected after starting the test, the error message will not show up

and the received results will be erroneous.

4.4 Error Messages "Change Current" and “Overcurrent”

This message is displayed if the voltage at the test object is too high during the test. In this case the test

current should be reduced and the test repeated.

The error message “Overcurrent” is displayed if the test voltage is lower than 10 V per channel but the test

current is still too high for that resistance. An user should re-start the test with lower test current selected.

4.5 Error Message "Overheat"

This message is displayed when the operating temperature of the RMO-TW rises too high. In this case, it is

necessary to wait for the test set to cool down and repeat the test.

Figure 4-7: Error message "Overheat"

Figure 4-5: Error message "Change Current"

Figure 4-6: Error message "Overcurrent"

Figure 4-4: Error message "Polarity"




4.6 Error Message "Mains Voltage < 90V"

This message is displayed when the RMO-TW mains voltage is below 90 V.

The RMO-TW should be restarted to reset the status message.

4.7 Error Messages "Error Printer" and "Check Paper"

The message "Error printer" is displayed if a hardware error of the printer is detected. The position of the black

shaft should be checked. If it is in proper position and the error keeps occurring repeatedly, please contact DV

Power Support Team (please refer to the ”Manufacturer Contact Information” section of this Manual).

The message "Check paper" is displayed if the printer is out of paper.

The paper roll should be aligned with the paper intake so that there is no horizontal offset, and the central axis

of the paper roll must be parallel to the printer as shown in the Figure 4-10. Also, attention should be paid when

inserting the paper into the printer. It should enter the paper intake from the lower side of a paper roll.

If the paper is not properly aligned, the black shaft should be pulled up to loosen the paper (see the Figure 4-

10). After that, the paper should be aligned and the black shaft pushed down into a proper position.

Figure 4-8: Error message "Mains Voltage < 90V"

Figure 4-10: Paper loading

Figure 4-9: Error messages "Error printer" and "Check paper"


RMO-TW Troubleshooting


5 Troubleshooting

If suspected the device is presenting inaccurate results, the following tests should be performed:

5.1 Accuracy Check

1. Connect the test shunt R1 (1 Ω) and the Voltage Sense cables (VS1 input) as shown in the Figure 5-1.

2. Set the first test current from the Table 5.1 and start the test. Read the resistance value measured with the

Winding Ohmmeter and compare it to the expected value written in the Table 5.1. Repeat this step for all

test currents from the Table 5.1.

3. Connect the test shunt R2 (1 mΩ) and Voltage Sense cables (VS1 input) as shown in the Figure 5-2.

4. Set the first test current listed in Table 5.2 and start the test. Read the resistance value measured with the

Winding Ohmmeter and compare it with the expected value written in the Table 5.1. Repeat this step for all

test currents from the Table 5.2.

5. Connect the Voltage Sense cables to the VS2 input and repeat steps 1-4.

6. If measured results differ from expected values, please proceed to the next step – determining the root

cause of the inaccurate measurements.

Figure 5-1 – Connection diagram

Figure 5-2 – Connection diagram

I [mA] R1 [Ω]

10 0.989 – 1.011

100 0.989 – 1.011

1000 0.989 – 1.011

I [A] R2 [mΩ]

2 0.989 – 1.011

5 0.989 – 1.011

10 0.989 – 1.011

Table 5.1 – Expected results Table 5.2 – Expected results

5.2 Open Circuit Voltage Check

1. Short circuit the Voltage Sense input (VS1) and connect a DC voltmeter directly between current terminals

of the Winding Ohmmeter, as shown in the Figure 5.3.

2. Set the test current of 10 A and start the test. Check if the voltage measured with the voltmeter is in range

55 – 65 VDC.

3. Check if any resistance measurement value is shown on the device display and if the discharge LED is ON.

4. After 120 seconds the device should display the Open connection error.

5. If the measured voltage is not in the range 55 – 65 VDC, please contact the DV Power Support Team.

Otherwise, please proceed to the next step.




Note: Discharge LED should not light during this test. Expected voltage: 55 VDC – 65 VDC

Figure 5.3 – Open circuit voltage check

5.3 Test Currents Check

1. Short circuit Voltage Sense input (VS1) of the device and connect a digital voltmeter in parallel to the R1 (1

Ω) test shunt as shown in the Figure 5.4.

2. Set the first test current listed in the Table 5.3 and start the test. Note the voltage V1 obtained with the

voltmeter and compare it with expected one: 𝑉1 = 𝐼 ∙ 𝑅1. Repeat this step for all test current listed in the

Table 5.3.

3. Short circuit Voltage Sense input (VS1) of the device and connect a digital voltmeter parallel to the R2 (1

mΩ) test shunt as shown in the Figure 5.5.

4. Set the first test current listed in the table 5.4 and start the test. Note the voltage V2 obtained with the

voltmeter and compare it to the expected one: 𝑉2 = 𝐼 ∙ 𝑅2. Repeat this step for all test current listed in Table

5.4.

5. If the measured voltages do not differ significantly from the expected ones, the device is generating the

current correctly. Please proceed to the next step.

Figure 5.4 – Connection diagram


I [mA] V1[mV]

10 9.89 – 10.11

100 98.9 – 101.1

1000 989 – 1011

I [A] R2[mV]

2 1.978 – 2.022

5 4.945 – 5.055

10 9.89 – 10.01





5.4 Voltage Measurement Check

1. Connect the test shunt R1 (1 Ω), Voltage Sense cables (VS1 input) and voltmeter as shown in the Figure

5.6.

2. Set the first test current listed in Table 5.5 and start the test. Note the resistance measured with the device

(R1meas), the voltage V1 measured with the voltmeter, and calculate the resistance: 𝑅1𝑐𝑎𝑙 = 𝑉1

𝐼. Repeat this

step for all test currents listed in Table 4.1.

3. Connect the test shunt R2 (1 mΩ), Voltage Sense cables (VS1 input) and voltmeter as shown in the Figure

5.7.

4. Set the first test current listed in Table 5.6 and start the test. Note the resistance measured with the device

(R2meas), the voltage V2 measured with the voltmeter, and calculate the resistance: 𝑅2𝑐𝑎𝑙 = 𝑉2

𝐼. Repeat this

step for all test currents listed in Table 5.6.

5. Connect the Voltage Sense cables to the VS2 input and repeat steps 1-4.

6. If calculated resistances do not differ significantly from the resistances measured with the RMO-TW device,

the device is measuring correctly.



I [mA] R1meas[Ω] V1[mV]

10 0.989 – 1.011 9.89 – 10.11

100 0.989 – 1.011 98.9 – 101.1

1000 0.989 – 1.011 989 – 1011

I [A] R2meas[mΩ] V2[mV]

2 0.989 – 1.011 1.978 – 2.022

5 0.989 – 1.011 4.945 – 5.055

10 0.989 – 1.011 9.89 – 10.01


5.5 TestCom Diagnostic Software

In case the TestCom diagnostic software is not provided, please contact the DV Power Support Team to

request the latest version.

1. Connect the device to the computer and turn it ON.

2. Run the TestCom.exe file.

3. Click Connect to establish communication between the device and the computer.

4. Click Start and a log file will be generated in the same folder where TestCom.exe is located.

5. Send the log file to DV Power Support Team for analysis.

NOTE: If experiencing problems with running TestCom.exe, please install the Patch.exe, which is

included in the TestCom archive. After the installation, it should be possible to run TestCom.exe.


RMO-TW Customer Service, Packing the Instrument for Shipment


6 Customer Service

Before calling or sending an e-mail to Customer Service for assistance, please perform the following steps:

1. Check all cable connections.

2. Try the test on another instrument, if available.

3. Perform the troubleshoot procedure

4. Have the following information available:

• Instrument serial numbers, hardware configuration, and software revision

• Exact description of the problem, including the test object information, error messages and the

sequence of events before it appeared

• List of solutions that have been tried

The Customer Support Department can be reached at:

Local support (Sweden): +46 8 731 78 24

International support: +46 70 0925 000

E-mail: [email protected]

Note: Email communication is preferred for support issues, since the case is then documented and traceable.

Also, the time zone problems and issues with occupied telephones do not occur.

7. Packing the Instrument for Shipment

If you need to send the instrument to DV Power for servicing, please contact the DV Power Customer Service

for return instructions at:

Local support (Sweden): +46 8 731 78 24

International support: +46 70 0925 000

E-mail: [email protected]

Note: DV Power is not responsible for shipping damage. Please protect each instrument from shipping and

handling hazards carefully. Please ensure protective covers are securely in place. Instruments should be sent

to DV Power freight pre-paid, unless other arrangements have been authorized in advance by DV Power

Customer Service.

To prepare an instrument for shipment, please follow these instructions:

1. Disconnect and remove all external cables. Do not include manuals and cables unless recommended by DV

Power Customer Service.

2. Reuse the original packing material if it is available. If it is not, pack the instrument for shipment according to

the instructions for fragile electronic equipment. It is recommended use two-wall minimum corrugated

cardboard box with a minimum 5 cm (2 inch) thick poly foam padding, or a wooden crate with minimum of 5 cm

(2 inch) thick poly foam padding all around.


mailto:[email protected]


RMO-TW Technical Data, Instrument & Accessories, Manufacturer Contact Information


8 Technical Data

8.1 Mains Power Supply - Connection: according to EN60320-1/C320

- Voltage: 90 V – 264 V AC, 50/60 Hz, Single phase

- Input power 750 VA (RMO10TW model), 1500 VA (RMO20TW model), 2250

VA (RMO30TW and RMO50TW models)

- Fuse 15 A / 250 V, type F, but not user replaceable

8.2 Output Data

- Test current

RMO10TW RMO20TW RMO30TW RMO50TW

5 mA – 10 A DC 5 mA – 20 A DC 5 mA – 30 A DC 5 mA – 50 A DC

- Output power

Instrument RMO10TW RMO20TW RMO30TW RMO50TW

Output power 600 W 750 W 850 W 1 000 W

8.3 Measurement

- Measuring range / Resolution

0.1 µΩ - 999.9 µΩ 0.1 µΩ

1.000 mΩ - 9.999 mΩ 1 µΩ

10.00 mΩ - 99.99 mΩ 10 µΩ

100.0 mΩ - 999.9 mΩ 0.1 mΩ

1.000 Ω - 9.999 Ω 1 mΩ

10,00 Ω - 99.99 Ω 10 mΩ

100.0 Ω - 999.9 Ω 0.1 Ω

1.000 kΩ - 9.999 kΩ 1 Ω

- Typical Accuracy: ± (0.1 % rdg + 0.1 % FS) for 0,1 μΩ – 1,999 kΩ range

± (0.1 % rdg + 0.2 % FS) for 2.000 kΩ – 9,999 kΩ range

- Guaranteed Accuracy ± (0.2 % rdg + 0.2 % FS)

8.4 Environmental Conditions

- Operating temperature -10 oC

- +55

oC / 14

F - +131 F

- Storage temperature -25 oC - +70

oC / -13

F - +158 F

- Humidity range 5 - 95%, non-condensing




8.5 Dimensions and Weight

RMO10TW RMO20TW RMO30TW RMO50TW

Dimensions without

handle (cm) 19.8 x 25.5 x 38 19.8 x 25.5 x 38 19.8 x 25.5 x 38 19.8 x 25.5 x 38

Dimensions without

handle (in) 7.8 x 10 x 15 7.8 x 10 x 15 7.8 x 10 x 15 7.8 x 10 x 15

Weight (kg) 7.5 7.5 8.5 8.5

Weight (lbs) 16.5 16.5 18.7 18.7

8.6 Applicable Standards

- Installation/overvoltage category II

- Pollution degree 2

- Safety UL 61010-1

CAN/CSA-C22.2 No. 61010-1, 2nd edition, including

Amendment 1

- EMC Directive 2004/108/EC (CE Conform)

Standard EN 61326-1 All specifications herein are valid at the ambient temperature of + 23 °C ± 5°C and by using the recommended accessories.

Specifications are subject to change without notice.




9 Instrument & Accessories

Instrument with included accessories Article No

Winding Ohmmeters RMO-TW

- DV-Win PC software including USB cable

- Mains power cable

- Ground (PE) cable

RMOXX0TW-N-00

Recommended accessories Article No

Current cables 2 x 10 m 10 mm2 and Sense cables 2 x 10 m with TTA clamps * CS-10-10LMWC

Current cables 2 x 10 m 2.5 mm2 and Sense cables 2 x 10 m with TTA clamps ** CS-10-02BPWC

Sense cables 2 x 10 m with TTA clamps S2-10-02BPWC

Current connection cable 5 m 6 mm2 with TTA clamps * CX-05-062XWC

Current connection cable 5 m 10 mm2 with TTA clamps ** CX-05-102XWC

Device bag DEVIC-BAG-00

Cable bag CABLE-BAG-00

* recommended for the RMO10TW and RMO20TW models

** recommended for the RMO30TW and RMO50TW models

Optional accessories Article No

Test shunt 1 mΩ (150 A / 150 mV) SHUNT-150-MK

Current cables 2 x 15 m 10 mm2 and Sense cables 2 x 10 m with TTA clamps CS-15-16LMWC

Current cables 2 x 20 m 16 mm2 and Sense cables 2 x 10 m with TTA clamps CS-20-16LMWC

Current cables 2 x 10 m 10 mm2 with TTA clamps C2-10-16LMWC





Current connection cable 12 m 16 mm2 CX-12-162XWC

Thermal printer 80 mm (built-in) PRINT-080-00

Cable plastic case CABLE-CAS-01

Cable plastic case with wheels CABLE-CAS-W1

Transport case HARD-CASE-RT

Bluetooth communication module BLUETOOTH-00




IBEKO Power AB 2014 This Manual is a publication of IBEKO Power AB, 181 50 Lidingö, Sweden. These documents are protected by Swedish Copyright law and international contracts as intellectual property of the IBEKO Power AB. The documents contain confidential information of IBEKO Power AB which is protected by patent, copyright, trademarks or otherwise as inventions, trademarks or creations of IBEKO Power AB. The reproduction, duplication, transmission or use of these documents or its contents is not permitted without express prior written consent of the IBEKO Power AB. IBEKO Power AB shall not be liable for any incidental or consequential damages resulting from the performance or use of this document or its product. This document has undergone extensive technical approval before being released. IBEKO Power AB reviews this document at regular intervals, and includes appropriate amendments in subsequent issues. While every effort has been made to keep the information herein as accurate and up to date as possible, IBEKO Power AB assumes no responsibility for errors or omissions or for damages resulting from the use of the information contained herein. IBEKO Power AB cannot take over liability resulting in any way from the use of this document or parts thereof. The product information, pictures, drawings and all technical data contained within this manual are not contractually binding and IBEKO Power AB reserves the right to make modifications at any time to the technology and/or configuration without prior notice. Insofar as any information, software or documentation is made available, any liability for defects as to quality or title of the information, software and documentation especially in relation to the correctness or absence of defects or the absence of claims or third party rights or in relation to completeness and/or fitness for purpose are excluded except for cases involving willful misconduct or fraud. In case of a disagreement between the translation and the original English version of this Manual, the original English version will prevail.

Manufacturer Contact Information

IBEKO Power AB

Box 1346, 181 25 Lidingö, Sweden Fax: + 46 8 731 77 99

E-Mail: [email protected] Website: http://www.dv-power.com



http://www.dv-power.com/

Documents

RMO-TW - WINDING OHMMETERS Manual - ITM Instruments