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OPERATING INSTRUCTION

FOR

AUTOMATIC VOLTAGE

REGULATOR

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PROJECT : O P JINDAL STPPPROJECT : O P JINDAL STPPPROJECT : O P JINDAL STPPPROJECT : O P JINDAL STPP

CUSTOMER : JINDAL POWER LTD.CUSTOMER : JINDAL POWER LTD.CUSTOMER : JINDAL POWER LTD.CUSTOMER : JINDAL POWER LTD.

W B S Nos. : CE/0228W B S Nos. : CE/0228W B S Nos. : CE/0228W B S Nos. : CE/0228----SH1SH1SH1SH1----48484848----01 01 01 01

TOTOTOTO

CE/0228CE/0228CE/0228CE/0228----SH4SH4SH4SH4----48484848----01010101

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Manufacturing Year : 2006Manufacturing Year : 2006Manufacturing Year : 2006Manufacturing Year : 2006----07070707

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T A B L E O F C O N T E N T S

1.1.1.1. General Information

1.1 Purpose of the Operating Instructions

1.2 Mechanical Structure

1.3 Design and Schematic Representation

1.3.1 Type Designations for DVR Equipment

1.3.2 Explanatory Notes on the Schematic Diagram

1.4 Brief Description of the Excitation System

2. Power Supply System

2.1 Principle of primary power supply

2.2 Power Supply Distribution System

3. Digital Voltage Regulator, DVR

3.1 Principle of Operation of the Regulator AVR

3.2 Basic Structure of the Processor Systems

3.3 Operation of the AUTOMATIC Channel

3.3.1 General Information

3.3.2 Voltage Set-Point

3.3.3 Regulator Tracking / Follow up

3.3.4 Ug/f Limiter

3.3.5 --NA--

3.3.6 Field Current Maximum Limiter

3.3.7 Inductive Stator Current Limiter

3.3.8 Capacitive Stator Current Limiter

3.3.9 Load Angle Limiter

3.3.10 Power System Stabilizer

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3,4 Gate control unit

4. Pulse Section

5. Thyristor converter

6. Field Current Circuit

6.1 Field Circuit-Breaker

6.2 De-excitation

7. Monitoring and Protection

7.1 Excitation Monitoring

7.1.1 General Information

7.1.2 Over current Alarms

7.1.3 Storage of Alarm Status

7.1.4 Actual Value Monitoring

8. Binary Controls

8.1 Operation for Fundamentals

8.2 Program Example

9. Operating Instructions

9.1 Operation from the Control Room

9.1.1 Field circuit breaker ON/OFF

9.1.2 Excitation ON/OFF

9.1.3 Channel I / Channel II ON

9.1.4 Channels “ RAISE “ / “LOWER”

9.1.5 Indicator Instruments

9.1.6 Alarms

9.1.7 Check-List for Operating Staff

9.2 Local Operator’s Panel, Exciter Cubicle

9.3 Micro-Terminal

9.3.1 Summary

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9.3.2 Selection of Addresses

9.3.3 Addresses with Variable Value (Parameters)

9.3.4 Processor Systems with Fixed Functional Modules

9.3.5 Binary Controls

9.3.6 Temporary Switch-over to Values Scaled in Percentages

9.3.7 Printer Output

10. Preventive Maintenance and Operational Malfunctions

10.1 Overview

10.2 Preventive Maintenance and Care

10.3 Operational Malfunctions and Functional Tests

10.3.1 General Information

10.3.2 Malfunctions in the Electronic Control

10.3.3 Functional Test at Standstill

10.3.4 Interpretation of the Alarm Displays

10.3.5 Alarm Indications

10.3.6 Other Malfunctions

11 Installation and Commissioning

11.1 Installation Site

11.2 Ambient Air

11.3 Commissioning

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1. General Information

1.1 Purpose of the Operating Instructions

These Operating Instructions (OI) for the excitation system describe the most essential functions of the excitation system and provide instructions for its correct operation, installation, and preventive maintenance. They are directed at trained operating staff who have a basic familiarity with electronics.

The description basically describes the specific principle of operation of the system supplied. Additional equipment, specially designated as “optional equipment”, has not necessarily been included in the unit at hand. In such cases one can find out from the schematic diagram and/or the test and commissioning report whether or not and how, the optional equipment in question has been provided with the unit supplied. The data sheets for the components and modules are standard descriptions that generally describe all variants and optional equipment, even though only a portion thereof has been included, specifically configured for the given installation.

In case of malfunctions, the Operating Instructions aid in quick and directed pinpointing of the fault. Whenever the fault lies within a printed electronic circuit board or another interchangeable module, remove the defective component and replace it with a spare. Troubleshooting and repair within the module itself requires special know-how and the use of special procedures that can only be ensured by the manufacturer.

The Operating Instructions also contain suggestions and recommendations for the installation and operation of the unit. They provide recommendations for the basic procedures and the rough scope of testing for initial commissioning. These instructions are, however, not a commissionin g manual and are based on the assumption that the commissioning staf f possesses special know-how and experience.

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1.2 Mechanical Structure

The excitation equipment comprises of Regulation cubicle REG, Field Supression Cubicle FS & Thyristor Cubicles TY1 & TY2. (Refer overall General Arrangement drg.)

The swing frame A containing the electronic tiers (refer to Scheme /YD101) is mounted on the front of the regulator cubicle REG. Other components of the open and closed-loop controls are mounted on the two side walls and the back wall. Essentially these include UNC 4661 and UNC 4662 binary input and output modules, two UNC 4660 analog input module, transformers, relays, protective switches, signal converters, etc.

The converter units TY1 & TY2 contain the thyristor bridges and their auxiliary components. These are firing pulse transformers, thyristor circuits, thyristor fuses,synchronizing transformers, reactors and current flow measurement coils for monitoring thyristor current.

The Field Supression cubicle unit FS contains components of the field circuit including the field circuit-breaker, the De- excitation resistor, transformers.

The binary control and signal connections between Regulation and Field Suppression/Thyristor Cubicles are made mainly across the UNC 4661/UNC 4662 input and output modules (with screw terminals). The signals without galvanic separation and the power supply connections from the electronic racks to the components within the system are made directly with FASTON or screw terminal connections.

On the back of tiers AA , AB & AF there are bus circuit boards in the upper portion for the standard connections for DVR modules(power supply units, data bus, etc.). Other signal connections specific to the given application are installed in the lower portion of these tiers, using WIRE-WRAP technology. 9- or 21-conductor (plug-in) system cables are used to interconnect the tiers. Tiers AG, AP have MAXI-TERMI-POINT connections. The view of swing frame (refer to the Scheme /YD101) shows the physical arrangement of the electronic equipment.

AUTO CHANNEL I is on the right in tier AA . The left half of the tier AA comprises of modules for AUTO CHANNEL II . Similarly MANUAL CHANNEL I is on the right in tier AF. The left half of tier AF comprises of modules for MANUAL CHANNEL – II.

The binary controls and alarm signaling have been placed in Tier AB at the left. Tier AD provides the local operator’s control and display panel (refer to scheme sht. No. /YD101).It contains the control/indicator unit with the command push buttons and status indication at the center, and space at the right for the portable Micro-Terminal. Excitation monitoring is at the right of tier AB . Firing pulses are processed in Tier AP which include final pulse (amplifier) stages and the power supply for the Final Pulse Stages. The power supply units of Tier AG supply the control voltage, Ucontr and the trip voltage, Utrip.

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1.3 Design and Schematic Representation

1.3.1 Type Designations for DVR Equipment

All apparatuses in swing frame A have a type designation that has been shown on the schematic diagram for the excitation equipment and marked on the module itself. Always use this designation when ordering or making inquiries. The following example (Micro-Terminal UNS 2660) will explain the coding system:

DVR (Name: Equipment System) • Type of Module A: Cubicle C: Chassis K: Tier L: Power part S: Special Unit None: Plugs into tier • Series of Numerals • Revision Status IMPORTANT: “b,c,...” supersedes “a”, but not vice-versa (=upward compatibility) - Sub-classification, Type of Unit: E: Electronic Unit in general G: Casing without Circuit Boards installed P: Plug-in Module Z: Casing with Boards installed • Variable Equipment i.e., special equipment of the module for a given standard function (“Spec.” -> adaptation as described in the test/commissioning report IMPORTANT: The variant number on the module used must always be the same as the variant number in the schematic diagram

Components other than modules such as switches, relays, transformers, etc., have designations and data of their own. The data for ordering these components can be obtained from the list of components for the schematic diagram (/YL001 ...).

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1.3.21.3.21.3.21.3.2 Explanatory Notes on theExplanatory Notes on theExplanatory Notes on theExplanatory Notes on the Schematic DiagramSchematic DiagramSchematic DiagramSchematic Diagram

The schematic diagram shows all essential functions of the hardware and software and all electrical connections of the components, including the interconnections for the given excitation system. For purposes of clarity for practical use, all unessential information has been deliberately omitted from the schematic diagram. Such details, generally needed only in special cases, can be obtained from the data sheets for the modules in question. Plant-specific hardware and software settings can be obtained from the test-/ commissioning report.

The schematic diagram comprises the following sections:

List of symbols used /YA006,/YA007

Cable list /YD002

Views of the swing frame /YD101,../YD115

Lists of components /YL001, ...

Block diagrams for the system

hardware /YU100, /YU103

Block diagrams for the system /YU105,../YU110

software

Lists of connections AU010,AU020, ..

Measurement circuits in general CE...

Hardware and software for the DE...

regulator channels

Hardware and software for the

alarm circuits/operator commands

and operation messages EG...

Hardware and software for

monitoring the electronics EW...

Hardware and software for

protection of the excitation EY...

Hardware and software, field circuit-

breaker and field flashing circuit GS...

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Hardware and software for power

supply in general GW...

Hardware and software for the

excitation monitoring and for

the converters, including converter

controls GX...

The view of the swing frame /YD101 shows not only the names of the modules but also, usually, a cross-reference to the page of the schematic diagram on which the pertinent connections for the module are to be found. The UN 0662 modules for the (freely programmable) binary controls (AB21 ... AB57) are an exception here. These are equipped but not specifically assigned to given pages of the diagram. For that reason, no cross-reference is made to the schematic diagram for these modules. Locations where no entry is made for the type of module but where a cross-reference to the schematic diagram appears are locations left open for standard optional equipment.

The organization of the schematic diagram, the designations for signals, and cross-references to the schematic diagram all confirm to the Kraftwerks-Kennzeichen-System (Power Plant Identification Code), KKS. As seen from the examples below, every signal has a signal designation and a diagram cross-reference. The signal designation gives the signal a specific and unambiguous name made up of the name of the functional group (e.g., GS020) and the signal code (e.g., XU12). The cross-reference to the diagram indicates the page in the schematic diagram on which the associated signal source, or sink, can be found. The signals are also described in plain text where that is helpful.

This plain text provides the user with information on the functional characteristics of the signal in question (it is not an identification of the signal!). Different text can be used to designate the same signal at the output and the input. There are often different texts at the signal branching points as well, to explain their specific functions at the signal sinks.

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Signal output from the binary Controls (1) Schematic diagram number

For identification, filing, and reordering the set of schematic diagrams pertinent to this installation

(2) Name of the functional group

All the components and functioning parts shown on the given page of the Schematic Diagram are functional components of this group. The listing for a “functional group” can be comprised of one page or several pages.

(3) Page Number

The pages for a given functional group are numbered in ascending order, starting with /YS.... Sheets showing functions of the binary controls start with /YS5.. .

(4) Designation of Location

Designation of the physical location common to the components or connections shown on the Schematic Diagram page. Example “AB”: Swing frame A, Tier B.

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(5) Assignment of connection for the signal

Together with (4) above identifies the plug-in location and connection (pin) for the signal (inputs at the left, outputs at the right on the schematic diagram). In the present example, “AB-X49:2b27” means:Tier AB location 49,2nd half of plug(lower position) pin row “:b” (or “a” or “c”), Pin No. 27.

NOTE:- For input or output signals generated or used internally (in the swing frame) this entry is the full identification of the hardware employed. Detailed information on these standard interfaces can be obtained from Data Sheets 692 .03 . NB1AA (UN 0662).

Generally, the entry for this hardware assignment is needed only for the factory tests. Hardware connections from pin to pin within a tier are made with WIRE-WRAP wires and identified with a “w”. Connections between the tiers (without the “w”) are via 9- or 21-conductor system cables, some of which are plugged onto the same pins (refer to the Cable List, Schematic Diagram /YD002).

(6) Processing priority

Processing cycle in the processor for the functional block in question. Functions with the 1st priority (“1.”)are processed at intervals of 20 ms. Functions with the 2nd and 3rd priorities (“2.”, “3.”) at programmable multiples of this 20 ms interval.

(7) Internal address

The value of the signal (for binary signals: the status) is stored under this address (RAM). This information is needed to program the function and for functional analysis via the Micro-Terminal (refer to Sect. 3.3).

(8) Output address to UN 0665 (without an “Assignme nt of Connection”)

The appropriate LED on a UN0665 signaling unit responds whenever the signal output is set at logical “1”. In the example “F74”: LED 16 (= HEX F) of the UN 0665 display unit with the “house address” HEX 740. This information is needed to program the function.

(9) Output address, binary or analog (with an “Assi gnment of Connection”)

This information defines the software address for the output, which depends on the “house address” selected and the pin number on the input/output module. (“Assignment of Connection”). In the example “35E”: Unit is 3 (= Output 4, refer to Data Sheet of UN 0662, the input/output module)and “house address” is HEX 5E0. This information is needed to program the function.

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(10) KKS designation for the signal

This consists of the functional group name (e.g.,GS020) and the signal code (e.g., XU12). For output signals, the functional group name is normally identical to the designation in the page heading (2). There is a different signal code for each signal within any given functional group. Naturally, the outputs for signal branching (as in the present example) have identical signal codes.

(11) Signal cross-reference

Designation of the sheet for the signal sink

(12) Plain text

Optional description of the function of the signal.

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Signal Input for the Binary Controls (Example): (1) Plain text

Optional description of the origin and signal meanings.

(2) KKS signal designation.

Consists of the name of the functional group which the signal is coming from and the signal name

(3) Signal cross-reference

Designation of the sheet for the signal sources.

(4) Input address, binary or analog (with an “Assig nment of Connection”)

This information defines the software address for the input, which depends on the” house address” selected and the pin number on the input/output module. In the example “02E”: Unit 0 (= Input 1, refer to Data Sheet of UN 0662) of the UN 0662 input/output module and “house address” HEX 2E0. This information is needed to program the function and for a functional analysis via the Micro-Terminal (refer to Sect. 3.3)

(5) Internal address

The same address number as the signal source. Used to program the function and for a functional analysis via the Micro-Terminal.

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(6) Input address, binary or analog (without an “As signment of

Connection”)

This input (address) is already being used at another location (Page). (The hardware assigned can be found there.)

Direct hardware signals on modules (Example):

(1) Location of the module

Together with the designation of location in the page heading (in this example, “AA”), this tells where the module is placed (In this example, “AA-29” means swing frame A, Tier A, Location 29).

(2) WIRE-WRAP Connection

The connections marked with a “w” are WIRE-WRAP connections. All connections in Tiers AA, AB without a “w” are connections made via system cables (refer to the Cable List, Schematic Diagram /YD002).

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1.4 Brief Description of the Excitation System

The Automatic Voltage Regulator regulates the voltage (and/or the flow of reactive power during parallel operation) from the synchronous machine (generator) by direct control of the Main exciter field current using (static) thyristor converters.

The voltage regulator is intended for the excitation control of generator equipped with an AC exciter employing rotating non controlled rectifiers. The excitation equipment of the generator and its interconnections with the voltage regulator is shown in the block diagram above. The PMG (permanent magnet generator )of the rotating system normally provides supply to the thyristor sets.

There are three main parts of voltage regulator euipment. They are Regulator, Thyristor, Field supression. Regulation is having 2 Automatic channels for controlling Generator voltage and 2 Manual channels for controlling Exciter Field current.. Each channel is provided with separate sensing unit, power supply unit and gate control unit.

Excitation of the generator is started by closing the field circuit-breaker –Q2. and by switching on Excitation which leads to releasing of pulses to thyristor gates. Field discharge is initiated on shutdown of the generator or in fault situations by the generator protection equipment. Field discharge commands drive the thyristor set/sets into the inversion mode. In addition to this, a tripping command is given to the Exciter Field Breaker. Field breaker while opening connects a discharge resistor R2 across the field of main exciter for effective field suppression.

The converter TY has been broken down for this purpose into two autonomous converter blocks TY1 & TY2 . Each converter block can cater 100% of the system requirement. Thus when both the converters are in operation 2X100%

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of system requirement is available. Each thyristor bridge consists of 6 devices working as three phase full wave fully controlled bridge. Each thyristor is protected by arm fuse and RC snubber circuit. Conduction of each arm of a thyristor bridge is monitored using conduction monitoring.

Channel 1 and Channel 2 (the AUTOMATIC channels) are built as voltage regulators and either of them can be ON during normal operation. In addition to the voltage regulator, which has a PID control algorithm, these AUTOMATIC channels also contain various limiters and adaptive power system stabilisers and corrective control circuits to ensure the use and stable operation of the synchronous machine up to its operating limits. Each of these channels possesses a Gate Control Unit with a subsequent Intermediate Pulse Stage to generate the firing pulses for the thyristor converter. During normal operation , the Intermediate Pulse Stage of the Channel in operation is active and transmits the firing pulses galvanically separated to the common pulse bus at the input to the Final Pulse Stage. Various monitoring functions of the channels initiate in case of a malfunction an automatic switch-over to hot stand by channel.

Channel 3 and Channel 4 (the MANUAL Channels) are built as simple field current regulators with a PI control algorithm. They serve as back-up channels in case of malfunction in Channel-1 and Channel-2. During normal operation in channel -I, the output pulses from Intermediate Pulse Stage of the Channel-2, 3 & 4 are blocked from reaching the pulse bus.

All the channels are equipped with tracking equipment so that the inactive channels always generate the same control variable as the active channel during steady-state operation. This ensures smooth switch-over from one channel to other . To ensure that the stand-by channel will, in a switch-over initiated by a malfunction, take over the operating point of the machine as it was prior to the problem, the response of the tracking is set relatively slow.

The excitation system has an autonomous Excitation Monitoring. As one of its functions, this equipment monitors for field currents that exceed acceptable maximum limits. It initiates an emergency switch-over to the stand by AUTO channel whenever the field current exceeds the preset limit. The most important measuring inputs for the excitation system (I

f, U

g, U

syn )are redundant

(2-fold). The Excitation Monitoring checks these measuring inputs for discrepancy and plausibility. An alarm is always initiated in case of malfunction. In certain cases, a switch-over to stand by AUTO channel is also initiated.

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2. Power Supply System

2.1 Principle of primary power supply (/YU101)

In Brushless excitation system here, the PMG provides the power supply for the converter.

A station battery supply is absolutely necessary for the control of the field circuit breaker. It is the power source for the electronic devices. In addition to this, 220V DC is also derived from the PMG Supply. The PMG supply is stepped down in transformer T5. This DC supply is paralleled with Station DC supply in UNC4664. The four synchronous voltages Usyn for CHANNEL-1 /CHANNEL-3 and CHANNEL-2/CHANNEL-4 are supplied separately across transformers T3 and T4. The Gate Control Units need these voltages to enable them to issue the pulses at a given firing angle relative to the input voltage of the converter.

For testing, the synchronous voltages and the AC power supply to the electronic equipment can be switched over to an auxiliary power supply while the generator is at a standstill (T2,T3,T4)with no voltage using switch -S20. The electronic equipment and the ignition circuits can then be tested while at standstill..

2.2 Power Supply Distribution System refer to block diagram (/YU101)

The electronic equipment is supplied redundantly from the 3-phase PMG supply and station battery. Transformer –T5 supplies the UNC 4664 power supply unit (GW030) with an AC voltage matched to the battery voltage. This module rectifies the AC voltage and connects it to the diode-decoupled battery voltage. The two voltages, brought together in this way, supply a common DC bus across an interference suppression filter. The power supplied is then distributed across protective circuit-breakers.

The electronic modules for the AUTOMATIC channel -1 (AA37), AUTOMATIC channel -2 (AA01), MANUAL channel-1 (AF37), MANUAL channel-2 (AF01), the binary controls and Excitation Monitoring (AB01) are each supplied autonomously from their own UN 0664 DC/DC power supply unit. These units isolate the secondary voltages needed (for power supply to the electronic equipment) galvanically from the primary voltage, and can work within a range from 75 to 140% of the nominal input voltage. There is a protective circuit breaker provided at the input to each power supply unit.

Two KX 9180 power supply units supply the voltages Ucontr and Utrip. The

control voltage Ucontr is used to supply the contact inputs (UNC 4661) oriented

to the system periphery and the contact outputs (UNC 4662). The voltage Utrip

supplies all other control circuits galvanically isolated from the electronic equipment. These include mainly all contact outputs wired to the field circuit-breaker trip relays (protective trip mechanisms) and UNC 4661/62 contact input/outputs for system-internal inputs or outputs of the electronic equipment.

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The KX 9180 power supply units also operate in a wide range of input voltages from 70 to 130%. Their input and output voltages are likewise isolated galvanically from one another. All power supply units have current limiters (short-circuit strength) and minimum voltage monitoring of their outputs. If one of the power supply units malfunctions, the output voltages are switched off. The malfunction is stored in the module, and an alarm is given.

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3. Digital Voltage Regulator, DVR

3.1 Principle of Operation of the Regulator AVR

To regulate the voltage and the reactive power of a synchronous machine, the field voltage must be adjusted quickly to the changes in the operating conditions (with a response time that does not exceed a few ms). To accomplish this, analog control systems include amplifiers which make continuous comparison of the actual values against the reference values and vary the control variable to the converter with almost no delay. Most of the delay that occurs originates in the converter, since the firing pulses for changing the rectifier phase angle are only issued periodically (every 2.8 or 3.3 ms).

The DVR digital voltage regulator calculates the control variable from the measured and reference data in very short time intervals. This results outwardly in a quasi-continuous behavior with a negligible delay time (as in an analog regulator).

The calculations are made in the binary number system. Analog measurement signals, such as those for generator voltage and generator current, are converted into binary signals in analog/digital converters. The set-points and limit values have already been defined in digital (binary) form.

An understanding of the actual computation processes in the digital voltage regulator is not necessary for either operation, preventive maintenance or troubleshooting. Like the operator of a pocket calculator or a personal computer, all the operator needs is to know how to operate the instrument and the programming for this working tool.

For that reason, we will explain below only the principle division of work among the various modules and the flow of data processing. The purpose is, above all, to make clear how the processor system has been integrated into the rest of the power electronics system.

3.2 Basic Structure of the Processor Systems refer to block diagram (/YD101)

The digital voltage regulator is broken down into several autonomous microprocessor systems. Two AUTOMATIC channels (Auto-1 & Auto-2), the programmable controls and the Excitation Monitoring each consist of the central UN 0660 microprocessor module and binary and analog input/output modules. Each of these processor systems has a common bus circuit board including the power supply bus, the address lines, the two data lines to the input and output, and the control lines. There is a specific range of addresses assigned to each processor working on the bus (a house address that can be adjusted using a switch). Whenever addresses from this range are called up, the signal processing module can exchange data with the microprocessor card across the two data lines.

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The inputs and outputs of the processor systems are directed across voltage-isolating peripheral units (wall-mounted units).

The two AUTOMATIC channels, each have their own UN 0664 power supply units. Signals are exchanged among these processor systems via hardwired connections or multi-conductor cables. Binary and analog input/output modules (UN 0662, UN 0610, and UN 0611) handle signal input and output. The signal processors themselves contain a limited number of hardware inputs and outputs with fixed equipment assignments.

The actual values measured from the two AUTOMATIC channels and two MANUAL channels are processed across a separate UNC 4660 peripheral unit for each channel. These peripheral units are used for preprocessing signals from external measurement circuits, i.e., for galvanic isolation and adaptation to the electronics level. The most important input parameters to the AUTOMATIC channel are the generator voltage Ug, the generator current Ig, the field current

If, and the synchronous voltage Usyn. From the UNC 4660 peripheral unit, Ug,

Ig, and Usyn are sent to the UN 0661 Interrupt Generator (plug-in module on

the processor bus) for filtering and further processing.

The UN 0661 Interrupt Generator also uses the 3-phase Ug signal to generate

the 12 interrupts per period to trigger the cycles for processing actual values in the AUTOMATIC channel processor. Synchronized with these interrupts (i.e., with the phase positions of generator voltage U

g) this processor measures the

generator current Ig, and then calculates the reactive current (I . sin φ) and the

active current (I . cos φ). With these two results, the processor is then able to derive further operating parameters, such as the load angle, the active power, etc.

The functions of all microprocessor systems other than the programmable controls have been accomplished in firmware. The non-varying standard function modules can be configured to the design desired, for plant-specific purposes, using software switches(K-Flags).Thus, for example, the stored status of a K-Flag determines whether or not a limiter is active, and whether the de-excitation or the excitation limiters take precedence. Because these K-flags determine the software Scope of Supply for the installation, they cannot be changed permanently via the Micro-Terminal. In this way, they differ from such setting data as the values of the parameters for the PID filter of the voltage regulator or the set-points for the limiters. These values can be permanently changed using the Micro-Terminal. Communication is possible with each of the UN 0660 processor systems via the Micro-Terminal by plugging on the connecting cable. In this way, signals within the processor and setting parameters can be viewed, analog signals can be issued, and the set parameters can be altered temporarily (F... range) or permanently (C... range).

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Unlike the other processor systems, the programmable controls (refer to Sect. 8) do not include any firmware for realization of the functions. They have been designed so that the designer (or the commissioning engineer) can himself adapt and change their functions easily using the “Functional Block Programming Language P10” (BHEL- standard). Digital and analog functions can be implemented in practically any degree of complexity desired using the P10 functional blocks.

The control variables of the voltage regulator (the two AUTOMATIC channels) are each processed in a UN 0663 Gate Control Unit and formed into a chain of pulses at the appropriate firing angle. The pulses of the active channel are directed to the pulse bus via the associated UN 0096 Intermediate Pulse Stage. The pulses for each converter block are amplified sufficiently in UN0809 Final Pulse Stage to fire the thyristors.

3.3 Operation of the AUTOMATIC Channels refer to block diagram (/YU105)

There are two operating Auto channels Auto-1 and Auto-2. These two channels are identical in all respect from the point of operation used.

3.3.1 General Information

The functions of the automatic voltage regulator AVR are:

• to regulate the generator voltage

• to regulate the effect of the reactive and/or active current on the voltage (droops)

• to limit Volt/Hz

• to limit max. field current

• to limit inductive stator current

• to limit capacitive stator current

• to limit the load angle

• to stabilize the power system

• to regulate Cosφ

Block Diagram /YU105 shows the software structure of the AUTOMATIC channels (Auto-1 & Auto-2). The generator limiters not provided for the installation in question (optional equipment) are identified in this overview as “Not Supplied.” The parameter values, signal values, and software switches (flags) marked with addresses (hexadecimal numbers) can be viewed and altered via the Micro-Terminal (refer also to Sect. 9.3). The values selected are displayed in %, sec, p.u., Hz, etc. and can, where necessary, be changed

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directly in these formats. The plant-specific settings of the variables and the flags can be obtained from the Test and Commissioning Report.

This block diagram provides the information about the important functions and possible settings of the AUTOMATIC channel. For the sake of clarity, no detailed presentation has been given of special functions such as tracking circuits, initializations, etc. The page heading cross-refers this overview to the various sheets of the schematic diagram. Binary signals are shown in broken lines, analog signals in solid lines. The corresponding text designations in the schematic diagram can be used for identification of the input signals (hardware inputs). The only analog output signal from the automatic voltage regulator, control variable U

contr, is sent via the data bus (CRU bus) to the Gate Control

Unit (refer to Data Sheet). Most of the binary messages (outputs) from the AVR are of no interest functionally and they have been omitted for the sake of clarity.

The basic structure of the digital voltage regulator and the limiters is simple. This is necessary in order that the behavior of the regulators/limiters will remain calculable and understandable in all operating situations and that there will be no problem in adjusting and optimizing them. The central PID filter in the digital voltage regulator defines the dynamic response of the closed-loop controls both in the voltage regulator mode and after limiters have intervened. The “control deviation” at the input to the PID filter is either the control deviation for voltage, the control deviation of a de-excitation limiter (the value determined by minimum value selection), or the control deviation of an excitation limiter (the value determined by maximum value selection). Flag F730 (“PRIOR”) is used to determine whether the exciting (Min. value) or the de-exciting signal takes precedence on the min/max value limiter (normally: F730 = 1111, i.e., the de-exciting signal takes precedence).

With the exception of the Minimum Field Current Limiter, all other limiters have variable factoring multipliers of the signal outputs so that they can be adjusted individually together with the common PID filter, which has been optimized for voltage regulation. The setting parameters for this PID filter are as follows:

Vo = K

R Static amplification

1 Ta = ---- Integration time constant

Tc1

Vp Proportional amplification

1 Tb = ---- Differential time constant

Tc2

V∞ Amplification of high frequencies

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The BODE diagram below shows the assignment of settings in accordance with DIN/IEC standards based on a typical example:

The PID filter amplifications Vo, Vp, and V∞ can be adjusted in p.u. values. But the “ceiling factor” Vpl must be adjusted correctly with parameter F310 if the total amplification (circuit amplification) of the control circuit is actually to conform to this p.u. setting. This factor must agree with the “external” amplification, i.e., with the ceiling value of the transformer-/ converter circuit:

Ufmax

Vpl = _______ Ufo

in which Ufmax = ceiling field voltage Ufo = no-load field voltage

To attain a suitable response of the AVR when starting excitation (“EXCITER ON”), it may be necessary to change the proportional amplification of the regulator during this phase. Vp2 (transiently activated) and Vp1 (permanently activated) can be adjusted for this purpose. For example, the value of Vp2 takes effect immediately once the excitation is switched on and remains effective for a period as set at F30C. Once the period F30C (e.g., 5 sec) has expired, Vp shifts over to Vp1 (becomes the steady-state Vp) at the rate of change set on F30E.

The standard operating mode for the PID filter is voltage regulation, for which the discrepancy between the voltage set-point (F270) and the current value for generator voltage Ug (F90A) (the control deviation) is supplied at the input. To compensate for the voltage drop in the block transformer, or whenever several generators are operating to the same distributing bus, the generator voltage must be varied in proportion to the measured generator current (droop influence). To accomplish this, the voltage set-point is varied as a function of the measured reactive current IX and/or active current IR. Flag F712 enables

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the IX droop, Flag F710 the IR droop. The desired compensation is set in F282 and F286 respectively. Flags F284 and F288 are used to select whether this droop influence is to increase the voltage or to reduce it (compensation). Combined influence of the active and reactive currents is attained by enabling both droops, IX and IR.

Flag F716 activates a so-called “Soft-Start” at the starting of excitation. This “Soft-Start” ensures that the voltage set-point integrates from 0% to 100% within the time set on F290 when the excitation is switched on (“EXCITER ON”). A “smooth” excitation of the generator can be achieved in this way whenever there is no demand for a quick excitation.

3.3.23.3.23.3.23.3.2 Voltage SetVoltage SetVoltage SetVoltage Set----PointPointPointPoint

Various signals and settings control and limit the voltage set-point F270. For example, the values of F254 and F252 define the normal operating range possible for set-point adjustment (e.g., 90 ... 110%) using external control commands (control room, local operator’s panel, superposed control system). The effective set-point adjustment rate is governed by parameters F258/F25A. The set-point can be set at the values of F250 and F256 by activating appropriate control commands (“SET” input). Enabling Flag F71A and activating a binary input prior to switching on the excitation (“EXCITER OFF”) sets the U

g set-point at the value of UAUX. This makes it possible, for example,

to ensure that the generator voltage will agree exactly with the network voltage after the voltage build-up. An external value with variable amplification (F250) can be added to the U

g set-point by enabling F724 (for example, for stability

tests).

3.3.33.3.33.3.33.3.3 Regulator Tracking / Follow upRegulator Tracking / Follow upRegulator Tracking / Follow upRegulator Tracking / Follow up

A follow up control logic ensures that a smooth switch over to the stand by Auto channel will always be possible from the operating Auto channel. To track, the voltage set point is shifted by means of RAISE / LOWER pulses, so that control variable U

c at the output from PID filter is held steady and identical to

the control variable Uc

from the CHANNEL IN OPERATION. This tracking acts

slowly as the resultant transient control deviations resulting from amplification in the PID filter might cause severe interference with control variable U

c .

3.3.4 Ug/f Limiter

At under frequency, the Ug/f Limiter reduces the generator voltage so as to prevent saturation effects in the supply and measuring transformers. To adjust this limiter, the max. permissible generator voltage at rated frequency is defined and set using parameter F280. When any under-frequency occurs, the generator voltage is thus reduced in proportion to that setting. An appropriate adjustment on parameter F28E is used to achieve a delayed intervention of the Ug/f Limiter.

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3.3.5 Field Current Minimum Limiter ( Not applicable for this project )

The Field Current Minimum Limiter maintains the field current at a preset minimum level. Normally that minimum level is defined by the minimum current of the converter(Holding current of thyristors). Parameter F410 defines the adjusted minimum value. F758 is the enable flag for this limiter function.

3.3.6 Field Current Maximum Limiter

The Field Current Maximum Limiter is provided to protect the generator rotor from overcurrents occurring in steady-state and transient operation. High field currents are normally the result of a sharp drop in network voltage, or of an improper raising of the voltage set-point by the operating staff. The field current is held steady at the value TH1, i.e., at the maximum thermal value permissible for the excitation circuit and the rotor. In order that the generator can support the power network with its transient overload capacity during brief collapses in voltage, a temporary switch-over is made to the transient overcurrent limit MAX1 (a higher setting). When the generator or the converter is operating at a reduced capacity. These limits TH1/MAX1 can be switched over to the lower settings TH2/MAX2 by activating the corresponding binary signals.The switch-over from the thermal limit TH1/2 to the transient overcurrent limit MAX1/2 can be configured in one of three ways:

a) Depending on the overcurrent, with -dU/dt ENABLE

Flag programming: F418 = any setting desired ; F41A = 0000.

This variant enables the transient over current value MAX1/2 whenever a collapse of voltage in the network is detected. The ENABLE time is fixed, and can be set using parameter F408. Parameter F40C defines the limiting gradient for detection of the collapse -dU/dt. The example below shows the typical behavior of the limiter configured in this way:

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b) Dependent on the overcurrent time integral, with -dU/dt ENABLE:

Flag programming: F418 = inactive; F41A = 1111.

This variant likewise enables the transient overcurrent value only when a collapse of network voltage has been detected. However, the switch-back to the thermal limit is not made dependent upon the time itself, but on the calculated time integral ∫i²dt of the over current. Parameter F416 can be used to set the maximum ∫i²dt for the overcurrent in p.u. The setting on Parameter F414 in s/p.u. takes into account the time the rotor needs to cool down, i.e., the rate of temperature change in the case of intermittent over current operation. The example below shows how the timing of the switch-back to the thermal limit depends on the present value for over current ∫i²dt:

The over current time integral is based on the formula:

= ∫ i2 dt = - If 2 . t

0.9 IfTh

Example: The setting of =i²dt equivalent to Version a (F416) at a constant 1.6 times the nominal field current for 10 seconds (with TH1/2 = 105%) is:

1.6 / (0.9 * 1.05) 2 - 1 * 10 = 18.7 p.u.

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c) Dependent on the overcurrent time integral, without any preconditions

Flag programming :F418 = 1111 ; F41A = 1111

In this variant, the transient overcurrent becomes available without any prior conditions (without a -dU/dt ENABLE) with the time integral ∫i²dt.

3.3.7 Inductive Stator Current Limiter

The Inductive Stator Current Limiter holds the stator current Ig within permissible limits while the generator is in the “over-excited” operating range by reducing the field current accordingly. The setting TH (thermal limit) provides the limit against stationary over currents that might occur. To take advantage of the generator’s transient overload capacity, a switch-over is made to the higher setting MAX. The principle of operation of this switch-over to the value MAX, permissible only transiently, is identical to that employed for the field current limiter (refer to the description above).

When the drive output from the turbine is very high, stator current may exceed permissible limits even while inductive loading of the generator is low. In this case, if the stator current limiter is not kept from influencing the field current, the control circuit will oscillate back and forth between the Inductive Stator

Current Limiter (de-exciting) and the Capacitive Stator Current Limiter (exciting). Parameter F43C is used to set a function which will block the stator current limiter when the reactive current I× is low. The output signal of that function then dominates the control variable of the Ig-dependent limiter via a maximum value selection.

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3.3.8 Capacitive Stator Current Limiter

The Capacitive Stator Current Limiter holds the stator current Ig within permissible limits while the generator is in the “under-excited” operating range by increasing the field current as required. The positive behavior of this limiter (build-up of excitation) is due to the way in which the synchronous generator behaves in the under-excited operating range. In order to reduce the generator current Ig (less -Ix), the generator calls for an increase in the field current (refer also below: “Power Chart”). To prevent fluctuations when the reactive current Ix is low (as described above with regard to the Inductive Stator Current Limiter), this limiter also possesses a function that can influence the Ig-dependent control variable. This adjusted value for this function (F43C) is the same as that for the inductive stator current limiter.

3.3.9 Load Angle Limiter

The Load Angle Limiter prevents the synchronous machine from slipping out of phase due to slippage of the rotor. The load angle δ, the difference in phase between the rotor and the stator rotating field, results mainly from the driving torque (active power P) acting on the generator and the level of rotor current (field current). If the driving torque remains constant, a increase in the field current reduces the load angle δ. The current load angle δ at any moment is obtained from the generator current and generator voltage based on a simplified model of the generator. Whenever this calculated load angle δ (F886) exceeds the preset limit angle (F4A0), the limiter increases the field current until the load angle has dropped back to its permissible value. The quadrature reactance Xq of the generator (F4A4) and the network reactance Xe (F4A6) during normal operation must be adjusted on the regulator in order to obtain the load angle δ.

The graph below shows the Power Chart for a salient-pole machine with typical limiter characteristics:

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3.3.10 Power System Stabilizer (Optional Equipment)

The purpose of a Power System Stabilizer is to use the generator excitation to damp electromechanical oscillations between the network and the generator. Depending on the design of the generator and the requirements imposed for network stability, its main function will be either to damp the oscillations originating in the machine or those from the network.

A synchronous generator working in a combined power network is, in principle, an oscillating structure. In order to produce a torque, the magnetic field of the rotor and the stator must form a given angle (referred to as the rotor displacement or load angle δ). The electrical torque ME increases as the angle δ increases, just as with a torsion spring. Because the ME of the generator and the mechanical driving torque MA from the turbine are in equilibrium during steady-state operation, the angle δ remains in a given position. Whenever this state of equilibrium between MA and ME is disturbed, the load angle slips of this rest position, and changes thereby the electrical torque ME. The torque attempts to restore the load angle to a stationary position. Due to the mass inertia of the turbine/generator rotor, however, this can only take place a-periodically. It does so in the form of more or less effectively damped oscillations (again similar to the effect of mass inertia on a torsion spring).

In order to damp the oscillations, there must be a damping torque produced depending not on the electrical torque ME associated with the angle, but on the difference in frequency (Df) between the rotor and the stator rotating field, i.e., on the slippage. This torque is produced mainly by the so-called damper winding in the rotor, but the dimensioning of this is subject to limits imposed by considerations of design and economy. Some further action is therefore needed to increase the damping effect.

The following drastically simplified formula shows the parameters upon which the amount of active power PE supplied by the generator depends:

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PE = active power

If

.

Ug

If

= field current

PE = --------- sin δ Ug

= terminal voltage

Xd Xd = direct-axis reactance δ = load angle

It can be seen from the above relationship that the active power that the generator transfers depends not only on the load angle δ, but also on the field current If. That means that a transient change can be made in the active power PE and with that in the effective electrical torque ME by varying the field current.

The principle of operation of the DVR Power System Stabilizer becomes clear from a consideration of the oscillations in power output and frequency (∆PE, ∆f) and the vector diagram:

If it is assumed, that oscillations in the network frequency generates load oscillations with the mass inertia of the rotor, then the active load of the generator (e.g. MW-measured ) is influenced with a sinusoidal value -∆PE (ME-MA = -∆PE). By inversion of -∆PE, one obtains the fluctuation in power provided by the rotor, +∆PE. As is known, the slip signal ∆f follows +∆PE with a phase delayed by 90°. The +ME produced by the perio dic changes in the load angle δ is in phase with +∆PE. A good damping is attained if ME is varied in phase with the slip ∆f. However, this signal must also be advanced somewhat to compensate for the time constants in the excitation circuit and the generator.

As mentioned above, the electrical torque ME can be influenced by varying the field current. To accomplish this, a suitable control signal, referred to as a variable disturbance compensation, must be imposed upon the voltage set-point or the converter control variable Ucontr.

As can be seen from the vector diagram, by applying proper weighting factors

(K1, K2), and then adding together the signals -∆PE and ∆f, an overall stabilization signal can be produced that rotates in advance of the Df signal by any angle desired between 0° and 90°. Because the a mplitude of -DPE remains proportional to the amplitude of ∆f, a constant angle in advance of ∆f results for the compensation of the time constants referred to above.

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The optimum weighting factors K1 and K2 for a synchronous generator working to a power network depend on its operating point at any moment and the external reactance of the network. Normally, the selection of a compromise setting is good enough to attain stability in all operating points and for all external reactance. For special demands, these settings must be parameterized as a function of the external reactance (which means, optional equipment: Xe-Identification). The BHEL-EDN computer program HE038 is used to calculate optimum values for K1 and K2 based on the generator data and the network reactance.

The Power System Stabilizer PSS is a section of the AVR computer program (see Block Diagram /YU105 ) and is processed once per network cycle. The voltage at the generator terminals and the generator current are measured in order to define the signals ∆PE and ∆f. The calculated signals for P (=PE) and ∆f are then sent across DC filters “D” (real differentiators) that transmit only the dynamic portion of the signals. The ∆PE and ∆f signals obtained in this way are then weighted (multiplied by) with the factors K1 (F336) and K2 (F352) and sent to the summing point of the voltage regulator.

To satisfy BHEL-EDN computer program HE038 for calculating the parameters K1 and K2, the polarity of the ∆f signal is selected automatically according to the status of Flag F732 (The digital voltage regulator has a non-inverting PID filter instead of inverting PID filter of analog controllers).

The PSS stabilization signal is imposed on the automatic voltage regulator only if the following prerequisites are met:

• Generator on line

• Generator power output > the value F338

• Generator voltage in a range between F33C and F33A

The stabilization signal is limited at the output from the PSS to the lower and upper limits of F336/F334. Flag F732 defines whether the stabilization signal is introduced before or after the PID filter (usually before the filter). Because the PID filter, as noted above (refer to Sect. 3.3.1) already takes the ceiling factor Vp1 into account, the PSS signal needs to be multiplied by Vp1 if it is added to the voltage regulator following the PID filter (divider at the input to the min/max limiter).

If the signal “MECH LOAD” (from the turbine) is available, this parameter can be imposed on the electrical load signal P by activating Flag F736. This precaution prevents the DC filter “D” in the P-channel from producing an unnecessary “stabilization” effect in the case of rapid changes in turbine load. As an alternative for the AVR’s Power System Stabilizer, a stabilization signal from an outside system can be imposed by activating the binary input “PSS-SIGN.EXT.” Flag F340 can be used to select between an analog and a 12-bit signal, and F33E to select the polarity desired for that signal.

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3.4 GATE CONTROL UNIT (refer to Data Sheet)

The generation of firing pulses, has been implemented in a electronic module, the UN 0663 Gate Control Unit. The control variable Ucontr of voltage

regulator is used as the reference value for generating firing pulses on the principle, known as “ramp control” (Comparison of Ucontr with Usyn-

synchronous sawtooth signal).

For further processing in the UN 0096 Intermediate Pulse Stage, the Gate Control Unit supplies six firing pulses at its output whose phase position with respect to the synchronous voltage Usyn is in accordance with control variable

Ucontr. An internal linearization ensures that the field voltage produced via the

firing pulses remains proportional to the control variable Ucontr throughout the

entire range. As a result, the circuit amplification of the control remains constant over the entire range.

The UN 0663 Gate Control Unit can be re-configured ( by pre-selection with a switch ) for purposes of testing to act as a purely firing pulse control. In this case, the control variable Ucontr is adjusted directly using the RAISE/LOWER

push buttons on the front of the module. In this way, for example, the relationship between the phase position of the firing pulses and the control variable Ucontr can be checked easily.

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4. Pulse Section

4.1 Pulse Generation and Amplification refer to block diagram (/YU101

The UN 0663 Gate Control Units of the AUTOMATIC and MANUALchannels supply six firing pulses for operating the 6-pulse thyristor bridges. The low-power pulse signals from these Gate Control Units are amplified in the UN 0096. Intermediate Pulse Stage, galvanically isolated, and then sent to the common pulse bus. On the output end, the Intermediate Pulse Stage of the non-active channel is always blocked. The pulses from common pulse bus is transmitted to Thyristor Gate circuit via the pulse final stage UN0809.

The Gate Control Units generate the pulses based on microprocessor control. The reference voltage used for the firing pulse phase location is the output voltage from the synchronising transformer (Usyn1, Usyn2, Usyn3 & Usyn4). The commutation spikes of the synchronous voltage caused by the converter are calculated prior to use of the voltage as a reference value and are deliberately filtered out.

The lower limit for the firing pulses( double pulses), which are offset from one another by 60°, is defined by the limit rectifier p osition (αmin) and the upper limit by the limit inverter position (αmax) for the firing angle. αmin and αmax can be adjusted on the Gate Control Units using DIL switches. αmin ensures that the firing pulses will not be issued (premature firing) until there is sufficient positive phase voltage on the thyristor involved. αmax prevents a dangerous “tipping” of the thyristor bridge into the rectifier mode if the firing angle α is too large (“late firing”). The critical factors determining αmax are the overlap time ümax (max. commutation time) and the “recovery time” of the thyristors (αmax < 180° - ümax - γ ).

The pulse signals are galvanically separated at the outputs from the UN 0096 Intermediate Pulse Stage (with pulse transmitters) and are then directed to the common pulse bus. This transmission of the pulse signals to the pulse bus via passive transmitters ensures a high degree of active channel autonomy. Practically no possible malfunctions on the inactive channel (including, for example, sustained pulses) affect the active channel.

An external control signal can force the firing pulses into their inverter limit position. Other binary inputs can block or direct the firing pulses of the Gate Control Units so as to produce freewheeling on the thyristor bridge. During freewheeling, the firing pulses for the thyristor pair R and S are blocked and the pulse signals T+/T- are engaged with chains of pulses.

Gate Control Units contain a field current monitor that blocks the firing pulses immediately whenever the current exceeds a preset threshold level. In this case tripping is also initiated. The purpose of these provisions is to prevent damage to thyristors and thyristor fuses in case of a slip-ring short-circuit, or to keep any damage that does occur to a minimum.

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The UN0809 is having a continuous pulse monitor which interrupts the input to the pulse transformers incase of a continuous pulse on the input or increase of a short circuit of the output transistors.

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5 Thyristor Converter

Fully controlled thyristor sets in three-phase bridge connection are used. Each of the 6 bridge arms is fitted with a thyristor and an arm fuse. The thyristors are generously dimensioned with respect to voltage and current so that the failure rate is very low.

Each thyristor bridge arm is equipped with current flow monitoring CT’s. The absense of conduction in any arm is identified by a Current flow monitoring module and alarm is given.

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6. Field Current Circuit

6.1 Field Circuit-Breaker refer to block diagram (/YU101)

The circuit-breaker in the field circuit is used to isolate the field circuit from the converter. It is capable of switching off the synchronous machine from full load under the maximum conditions of a 3-phase short-circuit.

In addition to its main contacts, the field circuit-breaker also has a de-excitation contact with which the field energy stored in the field can be dissipated across the de-excitation resistor. The de-excitation contact closes shortly before the main contacts open so as to ensure proper commutation of the field current from the main contacts to the de-excitation contact when the breaker is switched off.

The field circuit-breaker is switched on by electromagnetic force and is kept switched on by a mechanical latch. When the latch is released by a trip coil, the circuit-breaker is thrown. The circuit-breaker also has auxiliary contacts that report its status.

6.2 De-excitation refer to block diagram (/YU101)

When malfunctions occur, the stored field energy must be dissipated as quickly and safely as possible to protect the generator. This is done by the converter, the field circuit-breaker, and the de-excitation ( discharge ) resistor.

De-excitation (with opening of the field circuit-breaker) takes place in the following stages:

• The converter, driver to its inverter limit position (negative ceiling voltage), recovers a portion of the field energy into the network. A trip command is given to the field circuit-breaker.

• The de-excitation contact closes, diverting the field voltage to the de-excitation resistor.

• Then, immediately, the main contacts open, building voltage. The field voltage commutates to the de-excitation resistor.

• The current diminishes at a given time constant TE:

Lf

(with linear resistance: TE = -----------)

Rf + Re

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Due to the reversal of the field voltage by the converter, the field current commutates from the main contacts of the field circuit-breaker to the de-excitation resistor in a very early phase. This reversal of the field voltage prevents burn-off on the main contacts and provides effective protection for the field circuit-breaker.

Depending on the operating policy, an operational shut-down of the excitation can also be effected with the field circuit-breaker closed. This method is useful mainly when the excitation is switched on and off frequently. In this case, the converter is merely driven into the inverter limit position so that the field energy is recovered into the network. The converter then blocks since it is supplying positive current only.

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7. Monitoring and Protection

7.1 Excitation Monitoring

7.1.1 General Information refer to block diagram (/YU106, /YU107)

The main goal of Excitation Monitoring is to make optimum use of the redundancies provided in the excitation system and to give alarm whenever a malfunction makes these redundancies unavailable. For this purpose, preference for processing is given to the more plausible of two redundant measurements. The field current is monitored to see that it does not exceed a maximum level and, if necessary, a switch-over to the hot Stand by AUTO channel is initiated. In addition, the criterion for switching off the field flashing is generated. The Excitation Monitoring consists of an autonomous processor system (GX000) supplied with power from the same source as the Sequence Logic Control.

7.1.2 Overcurrent Alarms refer to block diagram (/YU106)

In the Excitation Monitoring, the limits for overcurrent are set at higher levels than the settings on the Field Current Maximum Limiter (refer to Sect. 3.3). Whenever the current exceeds 110% of the nominal field current, contact R1 and the binary output associated with it are activated immediately. If fieldcurrent remains > 110%, then, after a preset inverse-time has lapsed, relay R2 and - after a further delay (F21A) - relay R0 and the binary outputs associated with them are activated.

Parameters F212/F214 match the measurements for If1 and If2 to the nominal value for field current so that the internal values can be processed and read as p.u. values. Parameter F218 can be used to falsify the actual value of the field current If (to raise it) so as to cause a response from the overcurrent alarm limits for purposes of testing. The processed If signal (F022) is always taken from on the active channel (K1 or K2 ON).

As long as the field current If is above the threshold value 1.1 . Ifn, its peak value is measured. This is stored (until RESET) and can be read at any time on the Micro-Terminal (F40D).

Once the overcurrent value of If exceeds 1.1 . Ifn, integration of this overcurrent value starts. Whenever the integrated time-current value (∫i²dt) exceeds the preselected reference value , the alarm OVERCURRENT INVERSE-TIME is set off and a command is simultaneously issued to switch over to the hot Stand by AUTO channel (refer to Sect. 3.4).

Software switch F758 enables the three overcurrent alarm functions (R0, R1, R2) and selects one of three possible inverse-time curves T1, T2, or T3. Within the characteristic curve (T1, T2, T3) selected, the desired limit curve for response is set using the factor F216.

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7.1.3 Storage of Alarm Status refer to block diagram (/YU106, /YU107)

The outputs of the overcurrent alarms (R1, R2, R0) and the messages NO FAILURE MONITORING/ PARAMETERS CHANGED are stored (not shown on the Block Diagram). Stored messages can be erased by activating the input “GENERAL RESET” or by using the RESET button on the front of the module. Erasure with the input “GENERAL RESET” is effective only if the situation causing the alarm or the malfunction is no longer present. Whenever the self-diagnosis equipment in the UN 0660 processor detects a malfunction, the output NO FAILURE MONITORING is set at “logical 0” (= alarm). The alarm “PARAMETERS CHANGED” is activated whenever parameters or settings of software switches have been changed via the Micro-Terminal.

7.1.4 Actual Value Monitoring refer to block diagram (/YU107)

The actual values for generator voltage Ug, synchronous voltage Usyn, and field current If are monitored for malfunctions (plausibility). This monitoring is active regardless of whether or not the generator is in operation. Essentially, when the generator is in operation, the measurements are monitored by comparing the signals (the smaller signal reading is detected as incorrect). When the generator is not in operation, the measured data are monitored for extreme values.

The percentage of deviation permissible in the measurement signals being compared (Ug1&Usyn1, Ug1&Ug2, Ug2&Usyn2, If1&If2) is defined by parameters F208 and F20A. If the Thyristors are being supplied from a PMG power source (no shunt operation), the values of Ug and Usyn will be different in some operational conditions. In that case, Flag F75A can be used to deactivate comparative measurements Ug1 Usyn1 and Ug2 Usyn2.

The “primary monitoring” compares Ug1 with Ug2 and generates the messages that Channel 1 or Channel 2 has suffered a malfunction. Whenever Ug1 < Ug2 and the binary message from CH1 reports no malfunction, a malfunction on Measurement Channel 1 is reported (Ug1/Usyn1 FAILURE). A similar malfunction is also present whenever the binary message CH1 DISTURBANCE is reported and a discrepancy is detected between Ug1&Ug2. The generation of the alarm “Ug2 / Usyn2 FAILURE” is analogous to that for Channel 1.

The “secondary monitoring” compares Ug1/2 with Usyn1/2. This is enabled whenever the binary message of the comparison channel reports a malfunction, or whenever both binary messages report no malfunction - but both secondary monitors report a malfunction. As long as the secondary monitoring is blocked, the differences Ug1≠Usyn1 or Ug2≠Usyn2 trigger malfunction signals for the measurement channel involved (suspicion that there is a corresponding error in Usyn).

The measurement channel malfunctions are enabled operationally whenever, after excitation has been switched on, generator voltage Ug exceeds the value set on F204. The voltages Ug1 and Ug2 are checked 16 seconds after the excitation is switched off to see that they do not exceed the limit value F210

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that applies to both of them ( > remanence voltage). At the same time, Ug1/Ug2/Usyn1/Usyn2 are checked for extreme values (> or < the operating range). Monitoring for extreme values is likewise enabled during normal operation ( Excitation ON and Ug > F204 ). Flag F754 is used to enable or block the malfunction signals to the binary outputs.

Basically, the monitoring of the actual values for If1/If2 functions like that of the Ug1/Ug2 monitoring (refer above).

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8. Binary Controls

8.1 Fundamentals on Operation

The Binary Controls of the excitation system, which employ computer-

supported digital technology, form the link between the outside world and the voltage regulator. The Binary Controls receive commands from the control room or signals from transmitters and process them in the UN 0660 processor unit (Location AB/13). The functions are processed cyclically.

The inputs for commands from the control room or signals from transmitters are received via the UNC 4661 input interface and converted into potentially separate digital 24 V signals. These are supplied to the UN 0662 input /output module, which converts the input signals into a binary form and feeds them to the processor across the input lead (CRU-IN).

Once processed, the data are reissued via the UN 0662 module. From there, the output signals travel via the UNC 4662 output interface and the output relays to the control components, such as relays, circuit-breakers, etc., and to such external equipment as alarm records, control room warning lights, etc.

UN 0662 input/output modules are also used to exchange the binary signals with other processor systems such as, for example, the AVR, but the exchange takes place via nonisolated 24 V signals.

The software for the Binary Controls differs from the software of the other computer systems such as, for example, the AVR. The software for the AVR remains approximately the same for all its applications. That for the Binary Controls, on the other hand, depends to a great extent on the specific installation in question. The Binary Controls have been so conceived that the project planner himself can easily program them using BHEL-EDN’s Functional Block Programming Language P10. Both digital and analog signals can be processed in the programming language P10.

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The function of the Binary Controls are represented on the Schematic Diagram with DIN symbols. An identification code has been assigned to each symbol or function. To generate the program, this identification code is written into the first line of the program. The pertinent instructions are written into the subsequent lines of the program. These include information such as, for example, which memory addresses are to be assigned as inputs and which as outputs, what delay time is required for the function, etc. Each instruction consists of 4 hexadecimal characters, the first of which is referred to as the prefix. The prefix defines the nature of the instruction, e.g.: “2YYY” = true input from memory address YYY, “AZZZ” = output for internal memory address ZZZ.

8.2 PROGRAM EXAMPLE

Every input/output module has what is known as its “house address” for inputs and its “house address” for outputs. After the prefix, instructions for input and output signals contain the code for the input or output channel (1 character) and the “house address” (2 characters) of the corresponding input/output module. The example below shows the functional diagram with the functional blocks and the instruction code:

As described in Sect. 1.3.2, the functional representation illustration with Functional Blocks in the schematic diagrams generally include textual

descriptions of incoming and outgoing signals. Together with these supplementary texts, the functional representations on the schematic diagram provide the complete description of the functions of the Binary Controls.

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9. Operating Instructions

9.1 Operation from the Control Room

The control room has available a number of command push buttons, operating and malfunction signal lights, and instruments for operating the excitation equipment. These operating control units enable the operating staff to run the excitation equipment for the generator in either of the automatic modes (AUTOMATIC channel I or II ) depending on changes in operating conditions. Control room commands are enabled whenever the command input on the local operating panel is set at “REMOTE” (refer to Sect. 9.2).

9.1.1 Field Circuit-Breaker ON/OFF Commands with Status

Pressing the ON button closes the field circuit-breaker unless the blocking criteria shown in the functional representation in schematic diagram GS020/YS501 are present. Whenever this command is wired parallel to the command “EXCITATION ON” (refer to schematic diagram AU020/YB001), excitation is switched on at the same time as the field circuit-breaker (refer to the next section).

Pressing the OFF button switches off the field circuit-breaker and the excitation, which deenergizes the generator across the converter and the de-excitation resistor (refer to Sect. 6.3).

9.1.2 Excitation ON/OFF Commands with Status

Depending on the operating control philosophy for the installation in question, these commands can be issued together with the commands FIELD CIRCUIT-BREAKER ON/OFF as described above (refer to the input wiring in schematic diagram AU020/YB001). If the commands FIELD CIRCUIT-BREAKER ON/OFF and EXCITATION ON/OFF can be operated separately, the excitation can be switched on and off without having to activate the field circuit-breaker every time. This prevents undue stressing of the field circuit-breaker in cases where the excitation must be switched on and off frequently.

If the logic is so designed then the field circuit-breaker must be in the ON position before the excitation can be switched on. Provided there are no other blocking criteria present as shown in functional representations on schematic diagram GS021 /YS501, pressing the “EXCITATION ON” button switches the excitation system on, i.e., the enable is given for the firing pulses to the converter and for the field flashing equipment (refer to Sect. 6.2).

Pressing the OFF button switches off the excitation, i.e., the converter is directed to inverter operation, deenergizing the generator. If the excitation transformer has an auxiliary power source (with an AC breaker), it may also be necessary to open this breaker so as to remove the voltage from the converter.

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9.1.3 Channel I / Channel II ON Commands with Status

Basically, a shift can be made from one channel to the other at any time because the inactive channel is always matched automatically to the active channel. Whenever a malfunction is detected on the channel I , a switch-over to the channel II is forced, and it is no longer possible to switch back to the channel I , while the malfunction is not removed. The switch-over from channel I to II is not possible, too, when the latter is faulty. When both the channels are faulty trip command is issued. Normally, the control room has Balance voltmeter to monitor the differences between the two control variables Ucontr Channel I & Ucontr Channel II (refer to Sect. 9.1.6).

9.1.4 Channels “RAISE” / “LOWER” Commands with Status MIN/MAX

These “RAISE”/”LOWER” push buttons are used to adjust the set-point of the generator voltage. When the generator is operating under no load, this adjustment changes the generator voltage; in operation under load, it changes the reactive power output. When the operating limits of the rotor and the generator are being exploited to the full, appropriate limiters intervene and disable the “RAISE”/”LOWER” commands in the direction limited (refer to Sect. 3.3 for the limiters).

Warning signals light up whenever the generator voltage set-point is at its minimum or maximum value. If both the “RAISE” and “LOWER” commands are issued simultaneously, no adjustment is made in the set-point. The generator voltage set-point is set automatically at its nominal value whenever the excitation is switched on if preselect option is chosen.

9.1.5 Indicating Instruments

Usually the exciter current If, the generator voltage Ug, and the difference ∆V between the control variables of the two regulator channels are displayed in the control room. The ∆V indicator shows the voltage by which the regulator control variable of the channel-II differs from that of the channel -I.

The non operating channel is automatically matched to operating channel. This tracking is set to be relatively slow-acting: any switch-over from one channel to the other necessitated by a malfunction will be made to the steady-state value present prior to the malfunction. The generator can be operated in the AUTOMATIC mode up to the limits set in generator capability diagram. During “normal” steady-state operation of the generator, the ∆V Balance meter must always be at null position.

9.1.6 Alarms

The alarm messages in the control room are general messages grouped according to the information needed by the operating staff. The cause of the malfunction can be seen in detail on the malfunction indicator in the excitation

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cubicle. A detailed analysis of the malfunction can be undertaken using the Micro-Terminal (refer to Sect. 9.3).

EXCITATION LOW is displayed whenever an “exciting”limiter has intervened (refer to Sect. 3.3) to increase the field current. Response: If permissible in view of the generator’s reactive power output at the moment, raise the voltage set-point.

EXCITATION HIGH is displayed whenever a “de-exciting”limiter has intervened (refer to Sect. 3.3) to reduce the field current so as to dominate the voltage regulator. Response: If permissible in view of the generator’s reactive power output at the moment, lower the voltage set-point.

COMMON ALARM is displayed whenever an alarm (either high or low priority) has been given. Response: Do not start the unit. If it is in operation, find out the cause of the malfunction from the local alarm indicators at the excitation cubicle and proceed as called for in the List of Alarms in Sect. 10.3.4.

PROTECTIVE CHANGE-OVER is displayed whenever a switch-over has been made from operating channel to the standby channel due to a malfunction on the operating channel response. Find out the cause of the malfunction from the local alarm indicators at the excitation cubicle and proceed as called for in the List of Alarms in Sect. 10.3.4.

EXCITATION TRIP is displayed whenever the excitation and the generator have been tripped by a critical malfunction of the excitation system. Response: Find out the exact cause at the local alarm indicator on the exciter cubicle. In the case of a system malfunction, call for Service. In the case of a justifiable protective operating trip, acknowledge the malfunction signal and restart the unit (refer to the List of Alarms in Sect. 10.3.4).

9.1.7 Check-List for Operating Staff

Check for the following periodically during operation:

a) In the control room:

• Neither an “over-excitation” nor an “under-excitation” limiter has intervened.

• Set-points for the channels are not in their limit positions.

• The reading for channel tracking (DV) is steady in the middle of the dial.

• The field current, generator voltage, and reactive power output are stable.

• Test the indication / alarm LED’s.

Various monitors check the standby channel continuously to ensure that it is functional. Nevertheless, we recommend that a brief switch-over to the other channel be made periodically, e.g., after a start-up, to test its functional readiness.

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b) On the exciter cubicles:

• Regulator cubicle REG does not contain any active alarms (red LED’s).

• There are no unusual noises.

9.2 Local Operator’s Panel, Exciter Cubicle refer to block diagram (/YD115 )

The operator’s control tier contains command push buttons with status displays and three analog indicators for the most important, excitation-specific operating parameters. In addition, space has been provided for the portable Micro-Terminal (refer to the next Section). Whenever LOCAL operation has been selected, the command push buttons in the operator’s control panel have the same functions as the control room push buttons described in Sect. 9.1.1 to 9.1.4.

This operator’s control panel contains four additional command push buttons not among those in the control room:

REMOTE control, LOCAL control, to disable the push buttons in the operator’s control panel or in the control room

LAMP TEST, to check all LED displays in the operator’s control panel and the UN 0665 malfunction displays (AB61,AB65).

ACKNOWLEDGE/RESET, to acknowledge malfunction displays from the UN 0665 modules. Upon acknowledgment, malfunctions that are still present switch from flashing LED to steady LED. If the malfunctions are no longer present, the flashing or steady LED goes out.

RELEASE/RESET, to enable important commands with a 2-button command input, including the ON/OFF push buttons for the field circuit-breaker and the excitation, and the push buttons for channel switch-over.

ACKNOWLEDGE/RESET and RELEASE/RESET together reset high priority alarm messages such as overcurrent alarms, overcurrent trips, converter block malfunctions, pulse monitoring malfunctions, etc.

Note:- Malfunctions of the UN 0660 processor units, require acknowledgment with the RESET button on the fronts of the modules. Acknowledgment of the UN 0660 processor modules restarts the processing programs involved, e.g., stored values, processing information, and temporary changes made in the RAM storage (via the Micro-Terminal) are overwritten.

9.3 Micro-Terminal refer to block diagram (/YD115)

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9.3.1 Summary

The Micro-Terminal can be used to view parameters and signal values of the processor system (UN 0660) and to change stored values within certain address ranges. To do this, the Micro-Terminal must be connected to the UN 0660 processor in question by plugging a system cable in on its front side. This system cable also supplies the power to the Micro-Terminal. The Micro-Terminal has a 4-line LCD display in which 4 addresses (lines) appear simultaneously. The address appears at the left of these lines and the value for these addresses at the right. The four values displayed can be measured or recorded at the four measurement sockets provided below the LCD display.

9.3.2 Selection of Addresses

To select a given address on the display, the cursor must first be moved to the beginning of the line desired. Then the new address must be typed on the keyboard, and this address entered using the “RETURN” key. This causes the value for the newly selected address to be displayed at the right. The Micro-Terminal automatically translates a number of the addresses into easily interpreted alphanumeric values. For example, the actual value for generator voltage is at address F90A in the processor system for the AUTOMATIC channel. Whenever this address is selected, the term “Uact” appears in the address column, and the signal value, for example, 102.3% appears in alphanumeric form.

A new address can also be selected by moving the cursor to a given address in the address column and “paging through” the addresses with incremental commands (push buttons: INC / DEC). Because the addresses that can be selected via the Micro-Terminal are always even-numbered, the Micro-Terminal rounds up to the next even-numbered address.

9.3.3 Addresses with Variable Value (Parameters)

The processor systems contain EEPROMs and RAMs as storage spaces for variable parameters. When the processor is initialized, the RAM storages take over the content from the EEPROM storages. The values stored in the RAM are used for processing the functions in the processor. The Micro-Terminal can make changes in either the RAM storage or in the EEPROM storage. Changes in the RAM storage are temporary: they are canceled again the next time the process is initialized (The value in the EEPROM storage is taken over again). Changes in the RAM storage are therefore suitable mainly for test purposes. Changes in the EEPROM storage, on the other hand, are permanent. The address range for the EEPROM storage is from HEX C000 to HEX C7FE. The corresponding addresses in the RAM range are exactly HEX 3000 higher. For example, the RAM address F250 corresponds to the EEPROM address C250.

Changes in value in the RAM range are made by moving the cursor under the value to be changed, typing in the new value, and entering it with the “RET” key. As an alternative, a steady change in value can also be made by pressing the “INC”/”DEC” keys while the cursor is located under the value that is to be changed.

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Changes in value in the EEPROM range are made by pressing not the “RET” key alone, but the keys “SHIFT”, “WRITE”, and “RET”, in that sequence. The changed value in the EEPROM range then appears on the display, but is not yet functionally effective: The processor is still performing calculations using the “old” RAM storage value. The new value is not taken over into the RAM storage until the RAM storage is reinitialized, for example, by pressing the RESET button on the front of the UN 0660 processor involved.

The alarm, “PARAMETERS CHANGED,” is issued whenever values in the RAM or the EEPROM range have been changed. This alarm can only be acknowledged by pressing the RESET button on the front of the processor involved.

Note:- The address which generates the indication of the difference can be found via the micro-terminal:

Add. FB00 : 1111 - k-flag difference

Add. FB02 : XXXX - corresponding address

Add. FB04 : 1111 - EEPROM-RAM

Add. FB06 : XXXX - corresponding address

9.3.4 Processor Systems with Fixed Functional Modul es

The processor systems of the Channels I , II & the Excitation Monitoring contain software in the form of unalterable standard functional modules (firmware). The plant-specific overall function depends on the settings of the software switches, referred to as “configuration flags” (K-Flags). Because these K-Flags define the Scope of Supply for the plant software, they cannot be changed in the EEPROM range. The range of addresses for the K Flags in the RAM storage includes the addresses from F702 to F7FF.

The parameters of these processor systems as reference values, limit values, amplification factors, etc. can be altered and adjusted using the Micro-Terminal. There are usually max. permissible ranges of adjustment assigned to these parameter values. Whenever settings are selected beyond this range of adjustments, they are limited in the RAM range (functionally relevant) to the maximum value permitted for the range of adjustment. The values in the EEPROM range (C...) are marked with an asterisk (*) on the display as a reference for the individual using the Micro-Terminal.

In the processor system for the AUTOMATIC channel, the values of 12 signals can be selected directly using specific keys on the Micro-Terminal (without typing in an address). The list below shows these signal values and their essential characteristics:

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Display HEX Value Voltage microtermi Designation Add. in on Mic-terminal Dec Uref % U

g set point (without F270 2866 + 7V

droop) Uact % Actual generator voltage F90A 2866 + 7V I

fac % Actual rotor current F910 1228 + 3V

IGac % Actual stator current F91C 2866 + 7V (Apparent current) IR % Actual active current F906 ±1433 ± 7V IX % Actual reactive current F902 ±1433 ± 7V P % Active power output FA80 ±1002 ± 5V Q % Reactive power output FA82 ±1002 ± 5V Dact Deg Actual load angle (1p.u.= F886 1024 + 3V 1 rad = 360°/2p = 57.3°) C

Phi ind Power factor (-1024 ..0.. F842 ±1024 ±10V

\cap +1024 = 0 cap...1...0ind) U

contr Deg Control variable F992 0 ... ±10V

(input gate control unit) 4095 (0: α=180°;4095: α=0°) Uaux % Auxiliary voltage F91A 2866 + 7V

9.3.5 Binary Controls

Unlike the processor systems discussed in Sect. 9.3.4, the Binary Controls do not contain any standardized firmware. Thus, the Binary Control functions can be programmed to adapt to plant-specific situations. The programming is done on a programming device in the P10 block language. The values of parameters and signals and the source listing for the P10 user program can be viewed and parameters can be adjusted using the Micro-Terminal (refer to Sect. 8).

A distinction must be made between the following ranges of addresses when using the Micro-Terminal:

• Program addresses : 8000 ... 9FFE

• Parameter Range I : C400 ... C4FE

• Parameter Range II : C5AC ... C670:

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: F5AC ... F670

• Signal internal values: E000 ... EFFD

• Signal input values : F000 ... F5AA

: F672 ... FFFE

In the range of program addresses, the current programming of the user program can be viewed (in the P10 block language). To do this, add HEX 8000 to the HEX number for the desired program line (line in the program listing), and type the result in. The lines preceding and following the program line selected can then be called up by entering pulses with the “INC”/”DEC” keys. Sustained pressing of the “INC”/”DEC” keys causes a paging through of the addresses at a progressively changing frequency.

In parameter ranges I and II, preset parameters can be viewed and changed as has already been described for the parameters in Sect.3.3.3. In the case of parameter range I, however, it should be noted that no temporary change can be made in these values (no RAM range). Like other addresses in the EEPROM range, these addresses do not take effect until after a re-initialization of the processor. Unless a special command is issued via the Micro-Terminal (refer to Sect. 9.3.6), the values for parameters ranges I and II are displayed on the indicator in HEX format.

The signal internal values and signal input values can merely be viewed. To call up a value internal to a signal, type in an “E”, followed by the desired address as shown in the schematic diagram. To call up a signal input value, type in an “F”, followed by the desired address raised by HEX 60 (For example, for input address “231,” type in “F291”). When no special command is issued via the Micro-Terminal, these values are likewise displayed in HEX format.

A distinction must be made between analog and binary signal values (to be interpreted in accordance with the schematic diagram). Analog values are shown in 4-digit displays, binary values in 2x2 digit displays. In the binary signals, the two digits at the left of the value displayed correspond to the (even-numbered) line address; the two at the right to the next-higher (odd-numbered) address. A “logical 0” is displayed as “00”, a “logical 1” as “FF”.

Most signals in the “binary” controls are binary. For the few analog values included, a distinction must be made between percentage values, time values, and factors. These analog values appear on the display in HEX format, without a scale.

Whenever percentage values are to be read, there are these three possibilities available:

� conversion of the HEX display or the setting values using a pocket calculator that calculates hexadecimally

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� reading from an instrument plugged into the appropriate measurement socket on the Micro-Terminal

� temporary switch-over to display on a percentage scale as described in Sect. 9.3.6

The values in the percentage format for the Binary Controls are proportioned as follows:

% value Measurement Socket Display D-input +200% + 10 V ..0FFF - +100% + 5 V 07FF D7FF +0%/-0% ± 0 V 0000 D000/DFFF -100% - 5 V F801 D801 -200% - 10 V F000 -

Whenever values in the percentage format are entered as “direct input” using the “PREFIX” “D...” (refer to Sect. 8), it should be noted that the percentage value must be entered in a 3-digit instead of in a 4-digit form. The complete range that can be adjusted with HEX 000 ... FFF is limited to D200%. In order that negative values can also be realized with direct input, the max. adjustable positive range has therefore been limited to (D)7FF = + 100%. A negative range of 100% thus also becomes available. The HEX values in the negative range result from the “two’s-complement” of the corresponding positive value.

For example:

• 10% -> 2’s-compl. (+10% = 0CC) = 1000 - 0CC = F34 .

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The following table can be used to convert the time values (T) and the factors (K):

Z1 Z2 Z3

decimal + decimal + decimal

T K T K T K

0 0 8 0 0 0 0 0 0

256 8 9 16 0.5 1 1 0.0313 1

512 16 A 32 1.0 2 2 0.0625 2

768 24 B 48 1.5 3 3 0.0938 3

1024 32 C 64 2.0 4 4 0.125 4

1280 40 D 80 2.5 5 5 0.156 5

1536 48 E 96 3.0 6 6 0.188 6

1792 56 F 112 3.5 7 7 0.219 7

2048 64 0 128 4.0 8 8 0.250 8

2304 72 1 144 4.5 9 9 0.281 9

2560 80 2 160 5.0 A 10 0.313 A

2816 88 3 176 5.5 B 11 0.344 B

3072 96 4 192 6.0 C 12 0.375 C

3328 104 5 208 6.5 D 13 0.406 D

3584 112 6 224 7.0 E 14 0.438 E

3840 120 7 140 7.5 F 15 0.469 F

HEX HEX HEX

a b c

Example 1: (Value for a short-time functional block)

T = 1 sec => ∑Z = 1 sec/20 ms = 50 ∑Z = 50 => 0 (Z1) + 48 (Z2) + 2 (Z3) Zabc => 8 3 2

Hexadecimal value = HEX 0832

Example 2: (Value for a long-time functional block)

T = 40 sec => ∑ Z = 40 sec/ 1 sec = 40 ∑Z = 40 => 0 (Z1) + 32 (Z2) + 8 (Z3) Zabc = 8 2 8

hexadecimal value = HEX 0828

Example 3: (Value for factor)

K = 9.7 õZ = 9.7 => 8 (Z1) + 1.5 (Z2) + 0.2 (Z3) Zabc => 9 3 6

Hexadecimal value = HEX 0936

The procedure for finding scaled time values or factors from displayed hexadecimal values is the same as shown in the examples above, but in the reverse order.

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9.3.6 Temporary Switch-over to Values Scaled in Per centages

Values displayed in hexadecimal on the Micro-Terminal can be issued in the Binary Controls scaled in percentages. This switch-over to display in percentage values is activated by special push button commands via the Micro-Terminal. After a switch-over to percentage values, all output values, including the binary status, are reported in percentage format.

In the percentage mode (percentage format), individual lines in the display can be switched back specifically to hexadecimal display. The values named in Sect. 9.3.5 as belonging to parameter ranges I and II can be adjusted directly in the percentage format when operating in the percentage mode. A “conversion device: HEX format <-> percentage format” can be realized by selecting a non-used address in the parameter range, setting values, and changing the display mode.

To switch temporarily to the percentage mode (a permanent switch-over is not recommended):

� Connect the Micro-Terminal to the processor for the Binary Controls.

� Change address F700 from HEX 2222 to HEX DDDD.

� Press keys RET, SHIFT, 0, 1 in that sequence. All values now appear in a percentage format.

A line-by-line switch-over can now be made from the percentage format to the HEX format and back by moving the cursor under the value and then entering “D -> H” or “H -> D”.

The binary signals that appear in HEX format as 00 or FF now appear in percentage format as follows, line by line:

BINARY STATUS DISPLAY Address displayed Following address 0 0 0.0% 1 0 - 12.5% 0 1 + 12.5% 1 1 - 0.0%

To switch back to HEX format:

� Switch the value of address F700 to HEX format.

� Change the address F700 from HEX DDDD to HEX 2222

� Press keys RET, SHIFT, 0, 1 in that order, or

� Press processor RESET and disconnect the plug-in connector to the Micro-Terminal briefly.

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9.3.7 Printer Output

A printer can be connected to the plug-in connection “OUT” on the Micro-Terminal. This makes possible a documented check of the settings and the current program (listing) of the Binary Control. If the Micro-Terminal is connected to control channel 1, the most important measured data can also be printed out on call-up.

The following printer functions can be activated on the Micro-Terminal:

KEYBOARD INPUT Function SHIFT 1 0 Print screen SHIFT 1 1 Print out list of parameters SHIFT 1 2 Print actual values of the voltage regulator SHIFT 1 3 Print out User’s Program for binary controls SHIFT 1 A Adjust printer page length SHIFT 1 B Select “Elite” font

The special functions SHIFT 1 A and SHIFT 1 B do not normally have to be called up.

SHIFT 1 0, Print Screen:

The four values displayed on the screen are printed out as follows:

1st line of display 2nd line of display

3rd line of display 4th line of display

The display format (HEX or decimal) in the print-out is the same as that on the screen.

SHIFT 1 1, Print out List of Parameters:

In a processor system with firmware modules, e.g., the AUTOMATIC channel, all scaled values can be printed out. These include all preset values, the settings of the software switches (K-Flags), and the actual values of the signals.

SHIFT 1 2, Print Actual Values of the Voltage Regulator:

The Micro-Terminal must be connected to the AUTOMATIC channel. The scaled values of all signals at the given moment are printed out.

SHIFT 1 3, Print out User Program of the Binary Controls:

The Micro-Terminal must be connected to the processor for the Binary Controls. The P10 functional program in printed out, including address and program lines.

SHIFT 1 A, Adjust Printer Page Length:

This function sets an IBM-compatible printer as follows:

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Page length 12 inches: ESC C 0 12

Skip over performation: ESC N 12

This function can be called up to print out long lists of parameters that have not already been organized accordingly in the scaling table.

SHIFT 1 B, Select “Elite” font:

This function sets an IBM-compatible printer as follows:

Print pitch 12 characters per inch: ESC:

Connection of a Printer to the Micro-Terminal:

Connect the UNS 2660 serial interface (OUT) of the Micro-Terminal either to the parallel Centronics interface using an interface adapter SP100, or directly to the serial interface RS232 on the printer.

The following connections on the RS232 interface of the Micro-Terminal are needed:

Pin Designation Function

2 TXD Transmit data (Out)

5 CTS Clear to send (In)

7 GND Ground

The RS232 interface is defined as follows:

9600 Baud

8 Data bits

1 Stop bit

Even parity

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10. Preventive Maintenance and Operational Malfunct ions

10.1 Overview

While electronic components themselves do not suffer from aging and show only insignificant wear, the excitation equipment includes a number of such electro-mechanical elements as circuit-breakers, contactors, and fans, all of which are subject to a certain amount of wear.

If, even so, a malfunction should ever occur in the electronic section, there are various monitors and corresponding annunciation displays available. Certain functional parts, however, are difficult to monitor and must therefore be inspected periodically.

Fouling builds up as a result of the natural draft air cooling of the electronic equipment and the forced air cooling of the converter. Some of the screw-terminal connections can work themselves loose due to vibrations.

High voltages and currents (DC!) occur in the exciter circuit. Here, spots in the insulation that have become dirty present a risk of major damage from voltage flash-over. Periodic preventive maintenance on the installation reduces this risk greatly.

10.2 Preventive Maintenance and Care

We recommend the following preventive maintenance and care for the installation:

a) Every 3 months, with the turbine / generator group in operation

• Check for unusual converter fan noise. The fan bearings cannot be re-lubricated. The bearings must be replaced after approx. 20,000 service hours.

• Check for blocking of the vents in the cubicles. These may be washed out using a suitable cleaning fluid, or with a blower.

• Check the current distribution among the converter blocks and current conductance of the thyristors.

• If the converter blocks have measurement shunts or current display instruments, compare the present distribution of block currents based on those measurements.

• Check that the CHANNEL-II tracks properly the CHANNEL-I , and works properly when activated. For these tests, it is necessary to switch over to LOCAL operator control (Refer to Sect. 9.2) and to interfere with the tracking of the channel -II during channel -I operation by activating the “RAISE”/”LOWER” push buttons of CHANNEL-II . The automatic tracking is working correctly if the CHANNEL-II is slowly brought back

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equal to CHANNEL-I once the “RAISE”/”LOWER” buttons are released, so that the ∆V-Balance voltmeter on the operator’s panel returns to the middle. Then, check that the CHANNEL-II is working properly by switching over briefly to that channel. If there should be a significant change in the field current If (instrument on the operator’s panel), switch

back immediately to the CHANNEL-I and notify Service.

• Check that the important measured values are correct. To do this, read the measurements on the Micro-Terminal and compare them with the values on the instruments in the control room. Check at least the following values on the two channels: generator voltage F09A, stator current F91C, field current F910, and active power output FA80.

b) Once a year, with the turbine/generator group at a standstill

• Check for burn-off on the contacts of the field circuit-breaker and the field flashing switch.

• Check for dust deposits in the converter. If it is severely fouled, clean it, particularly the cooling elements, using dry, oil-free compressed air.

• Check for fouling of the plug-in modules (printed circuit boards and devices) in the swing frame. Only if necessary: blow the dirty components out with a dry, low-pressure air jet. In circuit boards or devices with gold-plated contacts (Tiers AG,AH, & AJ ) clean the contacts carefully using White Spirit or a contact cleaning fluid of proven quality. If the printed circuit boards are severely blocked (cannot be cleaned out with an air jet), use special cleaning procedures and then neutralize and dry them. Be very careful in taking the circuit boards out and putting them back in, and take the “Electrostatic Discharge” precautions indicated in Sect. 10.3.2 below.

• Check that all screw connections are firmly seated.

• Check all protective equipment in the trip and the signalization circuits.

• Perform a functional test on the complete electronic system as described in Sect. 10.3.3 below.

10.3 Operational Malfunctions and Functional Tests

10.3.1 General Information

Basically, malfunctions in the excitation system itself can cause temporary or sustained deviations of the exciter current, i.e., can cause over-excitation or under-excitation of the synchronous machine. There are generally standby circuits available when individual circuits fail (redundance) so as to avoid a trip due to the response of protective equipment.

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Malfunctions in the Binary Controls make themselves felt in a failure to respond normally to the control commands or in unintended trips or channel switch-over.

The operating staff must familiarize themselves with the details of how the excitation system works and with its operating controls well enough to enable them to evaluate the situation correctly in the case of a malfunction based on the readings of the instruments and the malfunction signals received. Always avoid precipitous action.

Most operational malfunctions in the functioning of the excitation system are detected correctly by the extensive monitoring and protection equipment and are annunciated at the signalizing devices (AB61, AB65) as a stored alarm. A Plain text description of these alarms has been provided close to the indicators. The various alarms are described and interpreted in more detail in Sect. 10.3.4 below.

The cause of the malfunction must be known before any general acknowledgment of the system is made. If it is not, determine and record the detailed “malfunction symptoms” as given in the List of Alarms in Sect.10.3.4.

If an electronic circuit board should become defective, we strongly recommend against attempting to repair it. Replace it with a spare part, which must then be set as shown on the Test and Commissioning Report and handled as described in the Section below.

10.3.2 Malfunctions in the Electronic Control

Cyclic self-test routines monitor for malfunctions of the digital electronics of the DVR system. A processor malfunction is announced on the front plate of the defective module by a “FAIL” LED, and is signaled to the alarm display UN 0665. In case of a malfunction on the channel-I, an automatic switch-over to channel-II is made. The defective module can thus be removed from the channel-I and replaced with a spare part while the generator is in operation.

The various power packs have voltage monitors of their own. They switch off automatically whenever the monitor responds and signal the malfunction in the alarm display UN 0665.

For circuit boards in Tiers AA , AB & AE switch off the protective circuit-breaker at the input of the corresponding UN 0664 module before taking out and replacing the electronic modules. The voltage must be OFF before attempting to replace them! The circuit boards in tiers AG,AP may in general not be replaced while the power supply is ON. In cases the module supply cannot be switched off selectively, the module must be pulled out and inserted “decisively” (with no hesitation).Before inserting the replacement module, make all the adjustments on it, such as switch settings, bridges, special equipment, etc. as described on the Test and Commissioning Report. (Also compare it with the “old” module!). In the case of the UN 0660 microprocessor circuit boards, also make certain that the correct operating program PROM (correct HIER No.) is installed in Location A735 and the correct user’s program PROM is installed in Location A736. Whenever the parameter values on the replacement circuit

EDN 07-657-008 61

board are not being preset via the Micro-Terminal (refer to Sect. 9.3), then the EEPROM in Location A738 must also be changed from the “old” module. The “old” settings of potentiometers R23 (U1), R24 (U2), R25 (UR), R26 (US), and R28 (UT) must be carried over on the UN 0661 “Interrupt generator” module.

Caution!

Most of the electronics modules contain CMOS elements that are highly sensitive to electrostatic discharge (ESD). Whenever these modules have to be handled, follow the “Guidelines for Handling ESD-Sensitive Electronic Components.

10.3.3 Functional Test at Standstill

Periodical functional testing is performed in order to increase the reliability of a system. It should be performed once a year, best of all during an overhaul of the turbogroup, i.e., while the machine is at standstill.

The main activities here involve:

• Testing the electronics equipment.

• Testing the power supplies and measurement circuits.

• Testing pulse generation and amplification.

• Testing the monitors.

• Checking the connections (cables, wires, connectors).

• Checking for wear on the mechanical parts (e.g., relays, switches).

• Checking the general condition of the installation (cleanness, oxidation, etc.).

For a functional test while the machine is at standstill set Q3-open first, switch -S12 at “TEST”.& MCB F74 on. The AC power supply for the electronics and the synchronous voltages Usyn are then obtained from an auxiliary network . For regularising the connection for normal operation first set the switch –S12 to service position; switch off mcb F74 and then close isolator Q3. Please note here that even though the firing circuit UN0663 (position AA65 and AE65) is designed for 400Hz operation, it can be operated on 50 Hz for testing AVR at stand still condition. (Refer to scheme sht. no. Appendix /YU101).

The digital control electronics have their own test routines that run cyclically and check during operation to make sure that the hardware is functional. For

EDN 07-657-008 62

that reason, the functions implemented in the processor do not have to be checked in routine controls. Either all the functions of a processor system function properly, or none of them do. The latter is accompanied by an alarm signal from the processor.

However, the measured data must be checked carefully. To do this, apply the associated 100% values for voltage and current at the input terminals using a 3-phase Variac or an electronic function generator.

To check that the conversion in the peripheral input modules and in the A/D transducer of the processor system is correct, compare the values applied with the display on the Micro-Terminal (refer also to Sect. 9.3). The addresses for the measured data in the three processor systems are as follows:

Measurement AUTOMATIC Monitoring channel (AA49) (AB73) Generator voltage F90A F844/F846 Stator current F91C - Field current F910 F840/F842

The values displayed in % on the Micro-Terminal correspond to the values in p.u. Compare them with the data in the Test and Commissioning Report.

The monitoring system likewise measures the two synchronous voltages Usyn1 and Usyn2 with the addresses F848/F84A. Because the synchronous voltages have now been switched over with testing switch -S12 to an auxiliary voltage of a different value, these displays deviate correspondingly from their 100% value.

The other data measured on the AUTOMATIC channel, such as active and reactive power output, load angle, etc., are derived by calculation from Ug and Ig and do not need to be checked in routine inspections.

If possible, however, check the correctness of the above-mentioned measurements, including that for effective power output FA80 (AA49) even before shutting down the group. If this checking produces proper results, no further rechecking of the actual values is necessary during the routine inspections.

The power supply units have a voltage monitor built into them. To test this monitor, open the protective circuit-breaker assigned to the power supply unit. Proper functioning of the monitor is signaled on the alarm display panel and/or on the module itself.

As a further check, measure the output voltages from the power supply units and compare them with the data in the Test and Commissioning Report.

To check pulse generation, connect up a 2-channel oscilloscope or a suitable recording instrument as follows:

1st channel: Synchronous voltage Usyn, phases UR-0V/US-0V/ UT-0V,

measured at the test sockets provided on the front plate of the UN0663 control unit

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2nd channel: Pulses R+ ... S- to 0 V, measured at the test sockets provided on the front plate of the UN 0663 control unit.

Triggering of Channel 1:

Perform the following tests:

� Set Q3-open, switch -S12 in the cubicle at “TEST” and close MCB F74.

� With regard to their phase-assigned synchronous voltage, the pulses must be in the preset limit position for inverter operation.

� The double pulses must be separated by 60°el. ± 5° el.

� Compare the shape of the pulses with the data on the Data Sheet for the UN 0663 .

Test both the AUTO-1 (AA65) and AUTO-2 channel (AE65).

To test the Intermediate Pulse Stage UN 0096, switch to channel-1 operation and view or record all output pulses at measurement sockets R+ ... S- to 0 V. Then switch to the channel-2 and view or record all output pulses at measurement sockets R+ ... S- on module. Compare the shape of these pulses with the data in the relevant Data Sheet.

To test the Pulse Final Stages UN 0809 check all output pulses at measurement sockets R+ ...S- to 0 V. Compare the shape of these pulses with the data in the data sheet .

Next measure the pulses on the thyristors themselves, i.e., downstream from the pulse transmitters. The pulse amplitude is still approx. 2 to 5 V. If there are firing pulses at all thyristors, the entire pulse path is OK.

To check channel switch-over, make another comparison of the output pulses from an Intermediate Pulse Stage with the associated synchronous voltage. Set the limit position for inverter operation at 120° o n one of the Gate Control Units and at 170° on the other. Then, when changing chann els, a shift in the pulse location from 120° to 170°, or vice versa, must be detected. (On completion of this test, restore all inverter operation limit positions to their original settings!)

During major overhauls, it is a good idea to test the inputs and outputs of the open-loop controls. The hardware and software for the associated signal processor are monitored continuously by built-in test routines, so that no testing is regarded in that regard.

To test the inputs, locate the sources of the messages using the schematic diagram and simulate a response of the annunciation contact. The corresponding LED on the UNC 4661 peripheral unit must then light up.

EDN 07-657-008 64

The outputs include the commands for the field circuit-breaker and the field flashing breaker. Since the OFF commands for the field circuit- breaker are in redundant circuits, they must be tested individually.

Work carefully when testing the protective equipment. To check the protective trips for over current, simulate a field current I

f equal to 105% I

fn at the isolating

terminals. Then change the following settings temporarily, one after the other, producing an exciter trip each time:

� the UN 0663 for the channel - I (AA65): S853 to “1”, causing an immediate trip;

� the UN 0663 for the channel - II (AE65): S853 to “1”, causing an immediate trip;

Simulate an overheating of the excitation transformer by disconnecting the measuring sensor at one of the input terminals .

For all trip simulations, always make certain that the trip coil of the field circuit-breaker pulls in and that a generator trip is initiated.

10.3.4 Interpretation of the Alarm Displays

Refer to the appropriate Data Sheets for an interpretation of the operating and malfunction displays (LED’s) on the fronts of the various modules.

The alarm displays on the UN 0665 modules (AB61,AB65...) and the other alarm and operating displays on the fronts of modules are used for quick pin-pointing of malfunctions. System malfunctions are signaled on the UN 0665 annunciation modules by LED’s. The Plain text descriptions of these alarms can be found on a sheet affixed to the inside of the cubicle.

When a malfunction is present, the corresponding LED flashes. The alarm can be acknowledged using the reset button “ACKNOWLEDGE/RESET” located in the local operator’s panel. The flashing light then shifts to a steady light until the command initiating is no longer present. Brief malfunctions are stored in memory and annunciated with a flashing light. The flashing light goes out once these temporary malfunctions have been acknowledged.

Chapter 10.3.5 describes all alarm indications in tabular form, telling how to interpret them and analyze the malfunction, and what operational actions are indicated. The purpose of the “List of Alarms” is to enable the Service staff and the trained operating staff to obtain a quick overall idea of the nature and the impact of a malfunction based on the malfunction signals. The List includes instructions as how to make a rough analysis of the malfunction and document it for more detailed investigation at a later time. Neither detailed knowledge of the excitation system nor time-consuming failure analyses based on the other plant documentation are required for this. In addition, the List of Alarms provides instructions as to what the reasonable operational response should be once a given malfunction has occurred.

EDN 07-657-008 65

For various disturbances the malfunctions indication is not only lit for the source itself, but also for the secondary malfunctions . In such cases, it is often difficult to identify the actual root of the problem quickly. In order that the cause of the malfunction can later (calmly) be traced down clearly, check and record the “Detailed Malfunction Symptoms” as shown in the List of Alarms for all alarm indications (AB61,AB65...) before restarting the installation and returning it to normal operation.

The location of non-signaled malfunctions requires a more detailed knowledge of the excitation system and a systematic procedure based on the plant documents (e.g., the schematic diagram).

Note the following when using the List of Alarms th at follows :

� “More Detailed Symptoms of the Malfunction”:

� “M-T → XYNN” means:

� Connect the Micro-Terminal to processor location designated by XYNN.

� The following general procedure always applies even though not expressly stated in the List:

� Note down all alarm indications that flash.

� Press the ACKNOWLEDGE/RESET button (without RELEASE/RESET!):

� Those malfunctions that are still present are now shown with a steady light.

� Check the symptoms listed for the malfunction indications that are still present and note them down.

� Press the ACKNOWLEDGE/RESET and the RELEASE/RESET buttons:

� The system is restarted.

“Further Procedure”:

Carry out the instructions step-by-step in the order shown. Once one step has proven successful (the malfunction has been located and/or eliminated), the steps that follow are no longer necessary.

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10.3.5 Alarm Indications

Alarm display: AB61 V01

CHANNEL-1 FAILURE

1. Possible Causes:

⇒ Ug actual value failure from monitoring

⇒ PT fuse failure CHANNEL-1

⇒ Synchronising supply MCB CHANNEL-1 tripped

⇒ CHANNEL-1 blocked

⇒ Loss of power supply CHANNEL-1

⇒ CPU failure CHANNEL-1

⇒ Interrupt failure CHANNEL-1

⇒ Over current inverse time

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to stand by CHANNEL

2.2 Manually

⇒ None

3. Further Procedure :

⇒ Check which fault has initiated CHANNEL-1 failure. Clear & reset the fault indication before switching back to channel-1

4. Documents:

Schematic drawing sheet ref - EW010/YS505

- AU020/YB002

- GX000/YS302

- DE010/YS503, /YS701

- EG040/YS403

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Alarm display: AB61 V02

LOSS OF POWER SUPPLY CHANNEL-1

1. Possible Causes:

⇒ Power supply unit AA37 failure

⇒ MCB F51 tripped

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to stand by CHANNEL

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check power supply unit. Reset the fault indication before switching back to CHANNEL-1.

4. Documents:

Schematic drawing sheet ref - DE010/YS503

- DE010/YS710

EDN 07-657-008 68

Alarm display: AB61 V03

UN0660 (CPU) CHANNEL-1 FAILURE

1. Possible Causes:

⇒ Computing unit UN0660 (AA49) failed.

⇒ Synchronising supply for CHANNEL-1 failed.

⇒ MCB F72/F74 tripped.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to stand by CHANNEL

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check computing unit. Reset the fault indication before switching back to CHANNEL-1.)

4. Documents:

Schematic drawing sheet ref - DE010/YS503

- DE010/YS710

EDN 07-657-008 69

Alarm display: AB61 V04

ASYNCHRONOUS INTERRUPT CHANNEL-1

1. Possible Causes:

⇒ Interrupt generator module UN 0661 (AA53) failed

⇒ Frequency out of range.

⇒ Missing generator voltage or generator voltage out of range.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to standby CHANNEL

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check interrupt generator unit and generator voltage settings. Reset the indication before switching back to channel- 1.

4. Documents:

Schematic drawing sheet ref - DE010/YS701

- EW010/YS505

EDN 07-657-008 70

Alarm display: AB61 V05

SYNCHRONOUS SUPPLY CHANNEL-1

1. Possible Causes:

⇒ Synchronising supply MCB F72/F74 tripped.

2. Immediate actions

2.1 Through excitation equipment

⇒ Emergency change over to stand by CHANNEL.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Switch on tripped MCB F72 /F74. Reset the fault indication before switching back to channel-1.

4. Documents

Schematic drawing sheet ref - CE100/YS601

- EW010/YS505

- EW030/YS505

- GX000/YS801

EDN 07-657-008 71

Alarm display: AB61 V06

UG ACTUAL VALUE FAILURE CHANNEL -1

1. Possible Causes:

⇒ AVR PT for CHANNEL –1 fuse failure .

⇒ Improper calibration of PT signal in UN0661(AA53).

2. Immediate actions

2.1 Through excitation equipment

⇒ Emergency change over to standby CHANNEL.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check which fault had caused loss of Ug actual value failure. Clear & reset the fault indication before switching back to channel-1.

4. Documents

Schematic drawing sheet ref - EW010/YS505

- AU020/YB002

- GX000/YS302

EDN 07-657-008 72

Alarm display: AB61 V07

IF ACTUAL VALUE FAILURE CHANNEL-1

1. Possible Causes:

⇒ Measured value of field current If is improper.

⇒ Current transformer in measuring circuit is defective.

⇒ Improper calibration of If signal .

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check which fault had caused loss of If actual value. Clear & reset the fault indication.

4. Documents:

Schematic drawing sheet ref - CE100/YS601

- DE010/YS602

- DE010/YS704

- GX000/YS302

EDN 07-657-008 73

Alarm display: AB61 V09

CHANNEL-1 FOLLOW-UP FAULTY

1. Possible Causes:

⇒ Faulty gate control circuit UN0663 (AA65).

⇒ Faulty digital I/O Module ( AA61).

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

⇒ Manual change over to Channel-1 blocked.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Ascertain the reason for the alarm indication.

4. Documents:

Schematic drawing sheet ref - DE010/YS703

- DE000/YS506

- DE010/YS704

- DE000/YS497

- DE010/YS711

EDN 07-657-008 74

Alarm display: AB61 V10

CHANNEL-2 FAILURE

1. Possible Causes:

⇒ Ug actual value failure from monitoring

⇒ PT fuse failure CHANNEL-2

⇒ Synchronising supply MCB CHANNEL-2 tripped

⇒ CHANNEL-2 blocked

⇒ Loss of power supply CHANNEL-2

⇒ CPU failure CHANNEL-2

⇒ Interrupt failure CHANNEL-2

⇒ Over current inverse time

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to stand by CHANNEL

2.2 Manually

⇒ None

3. Further Procedure :

⇒ Check which fault has initiated CHANNEL-2 failure. Clear & reset the fault indication before switching back to channel-2

4. Documents:

Schematic drawing sheet ref - EW020/YS505

- AU020/YB002

- GX000/YS302

- DE020/YS503, /YS701

- EG040/YS403

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Alarm display: AB61 V11

LOSS OF POWER SUPPLY CHANNEL-2

1. Possible Causes:

⇒ Power supply unit AA01 failure

⇒ MCB F52 tripped

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to stand by CHANNEL

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check power supply unit. Reset the fault indication before switching back to CHANNEL-2

4. Documents:

Schematic drawing sheet ref - DE020/YS503

- DE020/YS710

EDN 07-657-008 76

Alarm display: AB61 V12

UN0660 (CPU) CHANNEL-2 FAILURE

1. Possible Causes:

⇒ Computing unit UN0660 (AA13) failed.

⇒ Synchronising supply for CHANNEL-2 failed.

⇒ MCB F73/F75 tripped.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to stand by CHANNEL

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check computing unit. Reset the fault indication before switching back to CHANNEL-2)

4. Documents:

Schematic drawing sheet ref - DE020/YS503

- DE020/YS710

EDN 07-657-008 77

Alarm display: AB61 V13

ASYNCHRONOUS INTERRUPT CHANNEL-2

1. Possible Causes:

⇒ Interrupt generator module UN 0661 (AA17) failed

⇒ Frequency out of range.

⇒ Missing generator voltage or generator voltage out of range.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to standby CHANNEL

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check interrupt generator unit and generator voltage settings. Reset the indication before switching back to channel- 2.

4. Documents:

Schematic drawing sheet ref - DE020/YS701

- EW020/YS505

EDN 07-657-008 78

Alarm display: AB61 V14

SYNCHRONOUS SUPPLY CHANNEL-2

1. Possible Causes:

⇒ Synchronising supply MCB F73/F75 tripped.

2. Immediate actions

2.1 Through excitation equipment

⇒ Emergency change over to stand by CHANNEL.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Switch on tripped MCB F73 /F75. Reset the fault indication before switching back to channel-1.

4. Documents

Schematic drawing sheet ref - CE100/YS601

- EW020/YS505

EDN 07-657-008 79

Alarm display: AB61 V15

UG ACTUAL VALUE FAILURE CHANNEL -2

1. Possible Causes:

⇒ AVR PT for CHANNEL –2 fuse failure .

⇒ Improper calibration of PT signal in UN0661(AA17).

2. Immediate actions

2.1 Through excitation equipment

⇒ Emergency change over to standby CHANNEL.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check which fault had caused loss of Ug actual value failure. Clear & reset the fault indication before switching back to channel-2.

4. Documents

Schematic drawing sheet ref - EW020/YS505

- AU020/YB002

- GX000/YS302

EDN 07-657-008 80

Alarm display: AB61 V16

IF ACTUAL VALUE FAILURE CHANNEL-2

1. Possible Causes:

⇒ Measured value of field current If is improper.

⇒ Current transformer in measuring circuit is defective.

⇒ Improper calibration of If signal .

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check which fault had caused loss of If actual value. Clear & reset the fault indication.

4. Documents:

Schematic drawing sheet ref - CE100/YS601

- DE020/YS602

- DE020/YS704

- GX000/YS302

EDN 07-657-008 81

Alarm display: AB61 V18

CHANNEL-2 FOLLOW-UP FAULTY

1. Possible Causes:

⇒ Faulty gate control circuit UN0663 (AA29).

⇒ Faulty digital I/O Module ( AA25).

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

⇒ Manual change over to Channel-1 blocked.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Ascertain the reason for the alarm indication.

4. Documents:

Schematic drawing sheet ref - DE020/YS703

- DE000/YS506

- DE020/YS704

- DE000/YS498

- DE020/YS711

EDN 07-657-008 82

Alarm display: AB61 V19

CHANNEL-3 FAILURE

1. Possible Causes:

⇒ If actual value failure

⇒ Synchronising supply MCB CHANNEL-3 tripped

⇒ CHANNEL-3 blocked

⇒ Loss of power supply CHANNEL-3

⇒ Pulse generating module failure CHANNEL-3

⇒ MCB F82/F74 tripped

⇒ MCB F58 tripped

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-4 when AVR is in operation with CHANNEL-3

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-4 has already failed.

2.2 Manually

⇒ None

3. Further Procedure :

⇒ Check which fault has initiated CHANNEL-3 failure. Clear & reset the fault indication before switching back to channel-3

4. Documents:

Schematic drawing sheet ref - EW030/YS505

- GX000/YS501

- DE040/YS704, /YS710

- EG040/YS403

EDN 07-657-008 83

Alarm display: AB61 V20

LOSS OF POWER SUPPLY CHANNEL-3

1. Possible Causes:

⇒ Power supply unit AF37 failure

⇒ MCB F58 tripped

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-4 when AVR is in operation with CHANNEL-3

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-4 has already failed

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check power supply unit. Reset the fault indication before switching back to CHANNEL-3

4. Documents:

Schematic drawing sheet ref - DE040/YS704

- DE040/YS710

- EW030/YS505

EDN 07-657-008 84

Alarm display: AB61 V21

UN0663 CHANNEL-3 FAILURE

1. Possible Causes:

⇒ Failure of CHANNEL-3 pulse generating unit UN0663(AF65).

⇒ Improper / missing synchronising voltage for CHANNEL-3

2. Immediate actions

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-4 when AVR is in operation with CHANNEL-3

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-4 has already failed

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Reset the fault indication before switching back to channel-1.

4. Documents

Schematic drawing sheet ref - CE100/YS601

- EW030/YS505

- DE040/YS704

- GX000/YS801

EDN 07-657-008 85

Alarm display: AB61 V22

SYNCHRONOUS SUPPLY CHANNEL-3

1. Possible Causes:

⇒ Synchronising supply MCB F82 tripped.

⇒ Improper /missing synchronizing voltage for CHANNEL-3

2. Immediate actions

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-4 when AVR is in operation with CHANNEL-3

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-4 has already failed

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Switch on tripped MCB. Reset the fault indication before switching back to channel-3

4. Documents

Schematic drawing sheet ref - CE100/YS601

- EW030/YS505

- GX000/YS801

EDN 07-657-008 86

Alarm display: AB61 V23

IF ACTUAL VALUE FAILURE CHANNEL-3

1. Possible Causes:

⇒ Measured value of field current If is improper.

⇒ Current transformer in measuring circuit is defective.

⇒ Improper calibration of If signal.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-4 when AVR is in operation with CHANNEL-3

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-4 has already failed

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check which fault had caused loss of If actual value. Clear & reset the fault indication before switching back to channel-3.

4. Documents:

Schematic drawing sheet ref - CE100/YS601

- DE040/YS602

- GX000/YS501

EDN 07-657-008 87

Alarm display: AB61 V24

CHANNEL-3 FOLLOW-UP FAULTY

1. Possible Causes:

⇒ Faulty gate control circuit UN0663 (AF65).

⇒ Faulty CHANNEL-3 sensing UNC4660(U3).

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

⇒ Manual change over to Channel-3 blocked.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Ascertain the reason for the alarm indication. Clear & reset fault indication.

4. Documents:

Schematic drawing sheet ref - DE040/YS602

- DE040/YS704

- DE000/YS505

- DE000/YS506

EDN 07-657-008 88

Alarm display: AB61 V27

CHANNEL-4 FAILURE

1. Possible Causes:

⇒ If actual value failure

⇒ Synchronising supply MCB CHANNEL-4 tripped

⇒ CHANNEL-4 blocked

⇒ Loss of power supply CHANNEL-4

⇒ Pulse generating module failure CHANNEL-4

⇒ MCB F83/F75 tripped

⇒ MCB F59 tripped

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-3 (if healthy) when AVR is in operation with CHANNEL-4

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-3 has already failed.

2.2 Manually

⇒ None

3. Further Procedure :

⇒ Check which fault has initiated CHANNEL-4 failure. Clear & reset the fault indication before switching back to channel-4.

4. Documents:

Schematic drawing sheet ref - EW040/YS505

- GX000/YS801

- GX000/YS501

- DE050/YS704, /YS710

- EG040/YS403

EDN 07-657-008 89

Alarm display: AB61 V28

LOSS OF POWER SUPPLY CHANNEL-4

1. Possible Causes:

⇒ Power supply unit AF29 failure

⇒ MCB F59 tripped

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-3 when AVR is in operation with CHANNEL-4

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-3 has already failed.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check power supply unit. Reset the fault indication before switching back to CHANNEL-4

4. Documents:

Schematic drawing sheet ref - DE050/YS704

- DE050/YS710

EDN 07-657-008 90

Alarm display: AB61 V29

UN0663 CHANNEL- 4 FAILURE

1. Possible Causes:

⇒ Failure of CHANNEL-4 pulse generating unit UN0663(AF29).

⇒ Improper / missing synchronising voltage for CHANNEL-4

2. Immediate actions

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-3 when AVR is in operation with CHANNEL43

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-3 has already failed

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Reset the fault indication before switching back to channel-4.

4. Documents

Schematic drawing sheet ref - CE100/YS601

- EW040/YS505

- DE050/YS704

- GX000/YS801

EDN 07-657-008 91

Alarm display: AB61 V30

SYNCHRONOUS SUPPLY CHANNEL-4

1. Possible Causes:

⇒ Synchronising supply MCB F83 tripped.

⇒ Improper /missing synchronizing voltage for CHANNEL-4

2. Immediate actions

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-3 when AVR is in operation with CHANNEL-4

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-3 has already failed

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Switch on tripped MCB F83. Reset the fault indication before switching back to channel-4.

4. Documents

Schematic drawing sheet ref - CE100/YS601

- EW040/YS505

EDN 07-657-008 92

Alarm display: AB61 V31

IF ACTUAL VALUE FAILURE CHANNEL-4

1. Possible Causes:

⇒ Measured value of field current If is improper.

⇒ Current transformer in measuring circuit is defective.

⇒ Improper calibration of If signal .

2. Immediate actions:

2.1 Through excitation equipment

⇒ Emergency change over to CHANNEL-3 when AVR is in operation with CHANNEL-4

⇒ Alarm if AVR operation is in Channel-1/2

⇒ Trip in case of Channel-3 has already failed

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check which fault had caused loss of If actual value. Clear & reset the fault indication.

4. Documents:

Schematic drawing sheet ref - CE100/YS601

- DE050/YS602

- GX000/YS501

EDN 07-657-008 93

Alarm display: AB61 V32

CHANNEL- 4 FOLLOW-UP FAULTY

1. Possible Causes:

⇒ Faulty gate control circuit UN0663 (AF29).

⇒ Faulty CHANNEL-4 sensing UNC4660( U4).

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

⇒ Manual change over to Channel-1 blocked.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Ascertain the reason for the alarm indication.

4. Documents:

Schematic drawing sheet ref - DE050/YS602

- DE000/YS505

- DE000/YS506

- DE050/YS704

EDN 07-657-008 94

Alarm display: AB65 V01

AC INPUT SUPPLY ISOLATOR OPEN

1. Possible Causes:

⇒ Input supply Isolator open.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check whether isolator Q3 is opened.

⇒ Close the isolator.

4. Documents:

Schematic drawing sheet ref - CE100/YS601

- EG012/YS501

EDN 07-657-008 95

Alarm display: AB65 V02

DC SHORT CIRCUIT

1. Possible Causes:

⇒ Short circuit at main Exciter Field.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Pulse blocking.

⇒ Excitation trip.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Clear short circuit.

4. Documents:

Schematic drawing sheet ref - DE010/, DE020/, DE040/, DE050/YS704

- EG012/YS501

EDN 07-657-008 96

Alarm display: AB65 V05

CH-3 & CH-4 FAILED WHEN IN SERVICE

1. Possible Causes:

⇒ Refer possible clauses indicated against alarm display AB61 V19 and AB61 V27

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm when AVR is in Auto channel operation.

⇒ Excitation trip when AVR is in Manual channel operation.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check which fault has initiated CH-3 and CH-4 failure.

4. Documents:

Schematic drawing sheet ref - EW030/YS505

- EW040/YS505

- EY010/YS501

EDN 07-657-008 97

Alarm display: AB65 V08

EMERGENCY CHANNEL PROTECTIVE CHANGEOVER

1. Possible Causes:

⇒ Ref possible clauses indicated against alarm display AB61 V01 when AVR was in Channel-1. Similarly AB61 V10, AB61 V19, AB61 V27 for Channel-2,3 & 4.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Protective changeover to stand by channel (If channel I failed, changeover to channel II and vice versa.)

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Refer interpretation of various changeover criteria mentioned under corresponding alarm descriptions.

4. Documents:

Schematic drawing sheet ref - EG013/YS501

- EW010/YS505

- EW020/YS505

- EW030/YS505

- EW040/YS505

EDN 07-657-008 98

Alarm display: AB65 V09

OVER CURRENT MONITORING INVERSE TIME LAPSED

1. Possible Causes:

⇒ Short circuit in the main Exciter field circuit.

⇒ Excitation current limitation failure.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Channel changeover if the other channel is healthy.

⇒ Alarm indication

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check for AVR disturbances ( If- limiter failure).

⇒ Check for short circuit in the main Exciter field circuit.

4. Documents

Schematic drawing sheet ref. - EW010/YS505

- EW020/YS505

- GX000/YS302

EDN 07-657-008 99

Alarm display: AB65 V12

AVR IN TEST

1. Possible Causes:

⇒ Test/Service selector switch in TEST position.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm when Q3 is off.

⇒ Excitation trip when Q3 is on..

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check whether S20 switch is in TEST position.

4. Documents:

Schematic drawing sheet ref - CE100/YS601

- EY010/YS502

- GX000/YS601

EDN 07-657-008 100

Alarm display: AB65 V13

PARAMETER CHANGED

1. Possible Causes:

⇒ Stored RAM or EEPROM content of the channel-1/channel-2 or the monitoring has been changed.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm .

2.2 Manually

⇒ None

3. Further Procedure:

⇒ To reset the alarm of the channel –1, change over to any standby healthy channel. Press the reset button on CPU UN0660 (AA49).

⇒ To reset the alarm of the channel –2, change over to any standby healthy channel. Press the reset button on CPU UN0660 (AA13).

⇒ To reset the alarm of the Monitoring unit, Press the reset button on CPU UN0660 (AB73).

4. Documents:

Schematic drawing sheet ref - DE010/YS703

- EW010/YS502

- DE020/YS703

- GX000/YS302

EDN 07-657-008 101

Alarm display: AB65 V14

MONITORING UN0660 (CPU) FAILURE

1. Possible Causes:

⇒ Computing unit UN0660 (AB73) failed.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check computing unit. Replace the computing unit UN0660 (AB73)

4. Documents:

Schematic drawing sheet ref - EW010/YS502

- GX000/YS710

EDN 07-657-008 102

Alarm display: AB65 V15

FIELD BREAKER CLOSING SUPPLY FAILURE

1. Possible Causes:

⇒ Failure of field breaker closing supply.

⇒ Failure of fuses F14/F15.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check input battery supply across Input TB’S

⇒ Check healthiness of fuses F14 & F15

4. Documents:

Schematic drawing sheet ref - EG030/YS502

- GW030/YS501

- GW030/YS001

- EG011/YS503

EDN 07-657-008 103

Alarm display: AB65 V16

TIER FAN SUPPLY FAILURE

1. Possible Causes:

⇒ Failure of 415V,3 Ph aux. Supply to AVR.

⇒ Tier fan supply MCB F91 tripped.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check input AC supply across Input TB’S

⇒ Check MCB.

4. Documents:

Schematic drawing sheet ref - CE100/YS601

- GW010/YS004

- GW030/YS501

- GX000/YS801

EDN 07-657-008 104

Alarm display: AB65 V17

48V V1/V2 FAILURE

1. Possible Causes:

⇒ Failure of DC/DC converter KX9180(AG03/AG09)

⇒ MCB F79/F80 Tripped.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Common alarm stage-1 signal.

⇒ On failure of both KX9180, tripping of excitation is initiated

2.2 Manually

⇒ No action.

3. Further Procedure:

⇒ Check the DC/DC converter module and replace if necessary.

⇒ Check MCB F79/F80 and if tripped look for short circuit.

⇒ Check the input DC battery supply

4. Documents:

Schematic drawing sheet ref - GW030/YS505

- GW030/YS715

EDN 07-657-008 105

Alarm display: AB65 V18

Uc SUPPLY MCB TRIPPED

1. Possible Causes:

⇒ MCB F54 Tripped.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Common alarm stage-1 signal.

2.2 Manually

⇒ No action.

3. Further Procedure:

⇒ Check MCB F54 and if tripped look for short circuit.

4. Documents:

Schematic drawing sheet ref - GW030/YS004

- GW030/YS501

EDN 07-657-008 106

Alarm display: AB65 V19

Ut SUPPLY MCB TRIPPED

1. Possible Causes:

⇒ MCB F55 Tripped.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Common alarm stage-1 signal.

2.2 Manually

⇒ No action.

3. Further Procedure:

⇒ Check MCB F55 and if tripped look for short circuit

4. Documents:

Schematic drawing sheet ref - GW030/YS004

- GW030/YS501

EDN 07-657-008 107

Alarm display: AB65 V20

MCB REGULATOR SUPPLY FAILURE

1. Possible Causes:

⇒ Short circuit in the supply circuit protected by either one or more of MCBs F51, F52, F53, F54, F55, F56, F58, F59, F71 and F91.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Look for short circuit or faulty MCB.

4. Documents:

Schematic drawing sheet ref - GW010/YS004

- GW030/YS501

- GW030/YS002

- GW030/YS003

- GW030/YS004

EDN 07-657-008 108

Alarm display: AB65 V22

UN0901 PULSE SUPPLY –1 FAILURE

1. Possible Causes:

⇒ Failure of DC/DC converter UN0901 (AP07)

⇒ MCB F84 Tripped

2. Immediate actions:

2.1 Through excitation equipment

⇒ Common alarm stage-1 signal.

⇒ On both UN0901 failure, tripping of excitation

2.2 Manually

⇒ No action

3. Further Procedure:

⇒ Check the DC/DC converter module and replace if necessary

⇒ Check MCB F84 and if tripped look for short circuit

⇒ Check the input DC battery supply

4. Documents

Schematic drawing sheet ref - EG030/YS502

- GX000/YS502

- GX000/YS715

- GW030/YS003

EDN 07-657-008 109

Alarm display: AB65 V23

UN0901 PULSE SUPPLY –2 FAILURE

1. Possible Causes:

⇒ Failure of DC/DC converter UN0901 (AP10)

⇒ MCB F85 Tripped

2. Immediate actions:

2.1 Through excitation equipment

⇒ Common alarm stage-1 signal.

⇒ On both UN0901 failure, tripping of excitation

2.2 Manually

⇒ No action

3. Further Procedure:

⇒ Check the DC/DC converter module and replace if necessary

⇒ Check MCB F85 and if tripped look for short circuit

⇒ Check the input DC battery supply

4. Documents

Schematic drawing sheet ref - EG030/YS502

- GX000/YS502

- GX000/YS715

- GW030/YS003

EDN 07-657-008 110

Alarm display: AB65 V24

TRIP CIRCUIT SUPPLY UNHEALTHY

1. Possible Causes:

⇒ Failure of Field breaker trip supply.

⇒ Unhealthy tripping coil.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Common alarm stage-1 signal.

⇒ Blocking of field breaker ON.

2.2 Manually

⇒ No action

3. Further Procedure:

⇒ Check the supply and restore it.

⇒ Check trip coil.

4. Documents

Schematic drawing sheet ref - EY010/YS503

- GS020/YS002

- EY010/YS501

EDN 07-657-008 111

Alarm display: AB65 V27

AC/DC CONVERTER ISOLATOR OPEN

1. Possible Causes:

⇒ Thyristor bridge 1 AC/DC isolator Q21 open.

⇒ Thyristor bridge 2 AC/DC isolator Q22 open

2. Immediate actions:

2.1 Through excitation equipment

⇒ Common alarm stage-1 signal.

⇒ Pulse blocking of respective thyristor bridge.

2.2 Manually

⇒ No action

3. Further Procedure:

⇒ Check the isolator and close the same.

4. Documents

Schematic drawing sheet ref - GX000/YS502

- GX010/YS702

- GX020/YS702

EDN 07-657-008 112

Alarm display: AB65 V28

PULSE FINAL STAGE FAILURE

1. Possible Causes:

⇒ Failure of pulse final stage unit UN0809(AP20, AP03).n

2. Immediate actions:

2.1 Through excitation equipment

⇒ Common alarm stage-1 signal.

⇒ Pulse blocking of respective thyristor bridge.

2.2 Manually

⇒ No action

3. Further Procedure:

⇒ Check for healthiness of pulse final stage. Replace module if found faulty.

4. Documents

Schematic drawing sheet ref - GX000/YS502

- GX010/YS502

- GX020/YS502

- GX010/YS701

- GX020/YS701

EDN 07-657-008 113

Alarm display: AB65 V29

CURRENT FLOW MONITOR TY-1

1. Possible Causes:

⇒ One & more arm of the Thyristor bridge A21 is not conducting

⇒ Failure of arm fuses in A21 bridge.

⇒ Failure of thyristor devices in A21 bridge.

⇒ Missing pulses in A21 bridge.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check the healthiness of devices and replace device & fuse wherever necessary.

⇒ Check the healthiness of pulse transformer and for any missing pulses in pulse circuit.

4. Documents:

Schematic drawing sheet ref - EG030/YS502

- GX010/YS502

- GX000/YS711

- GX000/YS802

- GX010/YS702

EDN 07-657-008 114

Alarm display: AB65 V30

LOSS OF CONVERTER -1

1. Possible Causes:

⇒ Thyristor bridge –1(A21) AC/DC isolator open.

⇒ Thyristor bridge –1 pulse final stage UN0809 failed.

⇒ Thyristor bridge –1current flow monitoring picked up.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

⇒ Pulse blocking for failed thyristor bridge.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check the healthiness of devices and replace device & fuse wherever necessary.

⇒ Check the healthiness of pulse final stage and for any missing pulses in pulse circuit.

4. Documents:

Schematic drawing sheet ref - EG030/YS502

- GX010/YS502

- GX000/YS711

- GX010/YS701

- GX010/YS702

EDN 07-657-008 115

Alarm display: AB65 V31

CURRENT FLOW MONITOR TY-2

1. Possible Causes:

⇒ One or more arm of the Thyristor bridge- A22 is not conducting.

⇒ Failure of arm fuses in A22 bridge.

⇒ Failure of thyristor devices in A22 bridge.

⇒ Missing pulses in A22 bridge.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check the healthiness of devices and replace device & fuse wherever necessary.

⇒ Check the healthiness of pulse transformer and for any missing pulses in pulse circuit.

4. Documents:

Schematic drawing sheet ref - EG030/YS502

- GX020/YS502

- GX000/YS711A

EDN 07-657-008 116

Alarm display: AB65 V32

LOSS OF CONVERTER -2

1. Possible Causes:

⇒ Thyristor bridge –2(A22) AC/DC isolator open.

⇒ Thyristor bridge –2 pulse final stage UN0809 failed.

⇒ Thyristor bridge –2 current flow monitoring picked up.

2. Immediate actions:

2.1 Through excitation equipment

⇒ Alarm

⇒ Pulse blocking for failed thyristor bridge.

2.2 Manually

⇒ None

3. Further Procedure:

⇒ Check the healthiness of devices and replace device & fuse wherever necessary.

⇒ Check the healthiness of pulse final stage and for any missing pulses in pulse circuit.

4. Documents:

Schematic drawing sheet ref - EG030/YS502

- GX020/YS502

- GX000/YS711

- GX020/YS701

- GX020/YS702

EDN 07-657-008 117

10.3.6 Other Malfunction

Generator does not become excited

Possible Causes points to Check and Correct

- Break in field circuit - Does the field circuit breaker close? - Check cables for interruption.

- Generator becomes excited - Are firing pulses present at the output to a partial voltage but is the output from the Final Pulse Stages? deexcited again shortly Do they shift into the rectifier position thereafter. after the command “EXCITATION ON”? (Refer to Sect. 4.1)

- Failure of power supply to - Has the battery supply been switched on? the electronics equipment (Refer to overall Schematic Diagram ( LED’s on the power supply /YU101)

Units fail to light).

- There is still a converter - After “EXCITATION ON”, the following

blockage addresses in the binary controls must have a “logical 0”: E6A0, E6DO

(Refer to GX010/ GX020/ YS501)

- The set point for voltage or - After “EXCITATION ON,” the binary field current is not at the controls must issue setting commands

nominal no-load value. for Channel 1 and 2 with address E500 (refer to GS021/YS501). Setting value for

Channel 1,2 address F250(refer to YU105).

- Regulator malfunction - Is the control variable Ucontr of the active

UN 0663 Gate Control Unit (Channel 1 or 2 UN0663 AA65 or AA29) positive after “EXCITATION ON”? If not a functional test

with the Micro – terminal based on /YU105

Over voltage During Voltage build up Possible Cause Points to Check and Correct

- Over voltage due to voltage - Switch over to Channel 2 and build up

regulator voltage. Check the actual values on the Micro- Terminal while exciting the

EDN 07-657-008 118

generator on Channel 2.If set –point F270 is too high, Check F250, F256, F254.If

necessary, change the “soft start time” using F290.

- Gate Control Unit - If the control variable U

contr

malfunction correct (it can be measured at the socket,

Ucontr), check the firing pulses R+ ... S-

and their phase position. Check the synchronous voltages at UR, US, and UT.

Unstable parallel Operation with the Grid Periodic Fluctuations in Reactive / Active Power O utput

Possible Causes Points to Check and Correct

- Change in the controlled If the changes causing the problem system due to changes on the cannot be cancelled, restabilise the control grid or drive end loop. Then check and/or restabilise. the limiters as well. - Adjustments for Vo, Vp, Ta, Check the settings against theTest and and Tb have shifted. Commissioning Report.

Irregular Instability, i.e., Sporadic Over-excitati on or Under-excitation with Origin Not in the Grid

Possible Causes Points to Check and Correct

- The droop influence is causing Check active current IR and reactive an irregular voltage effect. current IX at Addres- see F906 and F902 ( refer to /YU105). Check external current transducer circuit and actual value for current I

g against the Test and

Commissioning Report.

- Generator is working in an Adjust the set-point and bring the genr. unacceptable operating range back within its normal operating range. ( normally prevented by Do a functional test on the limiter.

limiters). . .

- Repeated, short or long lasting For malfunctions that occur asystematically malfunction in the electronics check the control voltage Ucontr

on the Gate Control Unit and

EDN 07-657-008 119

the field voltage Uf using a recording device or an oscilloscope.

-If the two signals are in phase during the

malfunction, the fault is upstream from the Gate Control Unit. Do a functional test on the voltage regulator, particularly the set-point and actual value circuits and on the limiters.

-If the two signals are out of phase during the malfunction, the fault is downstream from the regulator, i.e., the regulator is attempting to correct the fault:. Do a functional test on the Gate Control Unit, the Final Pulse Stage, and the converter as described in Sect. 10.3.3.

- Over or under excitation - Check the set point and stage adaptation factor of the limiter involved against the the Commissioning Report.

EDN 07-657-008 120

11. Installation and Commissioning

11.1 Installation Site

With its thyristor converters, the exciter generates heavy high-voltage DC currents in the field current circuit. If the installation is subjected to the prolonged effects of dirt and corrosive gases, there is a risk of extensive damage caused by voltage flash-over. For that reason, select the location of the exciter in the power plant carefully and, if necessary, protect it from such dangers.

The converter portion should be located as close as possible to the sliprings and the exciter transformer so as to keep voltage losses to a minimum.

Because the excitation cubicles should be subjected to a little vibration as possible, it should not be firmly joined to the generator platform.

To counter fouling and corrosion, it is best in plants where these factors are critical to set the excitation cubicles up in an enclosed, ventilated room.

It goes without saying that the cubicles must be protected against splashing or spraying water, falling objects, etc.

11.2 Ambient Air

The air must be as dry as possible and free of pollution, aggressive gas,insects, etc. Salty vapors, e.g., due to cooling with salt water, damage the unit.

As a standard rule, the ambient temperature about the exciter must not exceed 50 °C (104 °F). Make certain that the warmed cooling air can flow off. Above the air pass out area an air space of at least one meter (approx.3 feet) must be left.

11.3 Commissioning

As already mentioned in Sect. 1.1, commissioning of the excitation equipment must, as a rule, be performed or supervised by staff who have special know-how and experience. Because the unit has already been extensively tested in the factory, activities during commissioning are limited mainly to functional tests on its interaction with the generator and, with that, the with equipment on the power plant end.

As a result, the time required for commissioning depends to a very significant degree on the cable connections outside the cubicles and on progress of the (other) generator commissioning in accordance with the program.

The steps in commissioning the excitation equipment are as follows:

• preliminary testing

EDN 07-657-008 121

• generator commissioning: test runs and testing of the generator protection system

• functional and stability tests during normal generator operation

Preliminary testing includes testing of the measurement, control, TRIP,and alarm circuits, and the functional test on the converter. The following conditions must be met before these tests are carried out:

• Connecting of cables must be completed and have been tested electrically.

• The binary input signals must have been tested as far as the LED’s on the UNC 4661 input modules

• The binary output signals must have been tested electrically, starting from the connection terminals (Jump the output contacts on the connection terminals).

• A substitute resistor (> 10A) must be available for the functional test of the converter.

Normally, the test runs for the generator include the recording of the generator’s short-circuit and open circuit characteristics and testing of the generator’s protective TRIPs.

Functional tests and stability tests can also be performed.

Note:- For subsequent installations of the same type, it is possible to a large extent to do without the stability tests since, with this digital system, there is a high degree of certainty that the later units will operate in a way identical to that of the first unit.

EDN 07-657-008 122

Approx. time required Tests ------------------------------------------------------------------------------ Operating Conditions n(p.u.) Ug(p.u.) P(p.u.) Q(p.u.) (h) - Checking voltage 1 0 to 1 0 0 2 regulators, AUTO-1 and AUTO-2 ; Stability, range of settings (oscillograms) - Oscillograms for 1 0 to 1 0 0 1 excitation start-up, de-excitation, AUT0-1 and AUTO-2 - Checking the V/Hz- 0.5 to 1 0.5 to 1 0 0 0.5 limiter - Effects of current 1 1 0.4 to 0.6 +0.4 to 0.6 1 on the grid - Voltage regulators: 1 1 as as 2 * checking stability with desired desired the grid - Reactive load shut-down 1 1 appr. 0 +0.4 0.5 * (with oscillogram) - Rotor current limiting 1 1 0 to 0.5 ± 0.5 1 * measurement, range of settings, stability (oscillograms) - Load angle limiting, 1 1 0.5 ± 0.5 1 * measurement, range of settings, stability (oscillograms) - Inductive stator 1 1 0.5 + 0.5 1 * current limiter - Capacitive stator 1 1 0.5 - 0.5 1.5 * current limiter - Power system stabilizer 1 1 0.5 appr. 0 2 * with sudden changes in Ug set point

* During these tests, surges in reactive load of approx. 0.1 to 0.3 p.u.must be expected.

n= speed Ug = Generator Voltage P= MW Q= MVAR