UNITROL® FExcitation systems for synchronous machineswith and without rotating exciter

Copyright © 2000 Photodisc, Inc.

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UNITROL® F System Overview

AUTO I

MAN I

AUTO II

MAN II

AUTO

MAN

SFE AUTOMATIC voltage regulator andMANUAL control (excitation current regulator)

AFT Dual channel system- Channel I AUTOMATIC and MANUAL control- Channel II AUTOMATIC and MANUAL control

Fig. 1:Main configurations ofthe UNITROL F system

UNITROL F provides a comprehensiverange of Automatic Voltage Regulatorsand Static Excitation Systems for highperformance control of all kinds ofsynchronous machines.

Product rangeThe UNITROL F system is available as

• Automatic Voltage Regulator (AVR)– for 50/60 Hz supply using thyristor

converter– for DC supply or higher frequency AC

supply using IGBT converter

• Static Excitation System (SES) for50/60 Hz supply using thyristor con-verter.

A wide selection of power componentsand software functions is available toprovide a system which meets the mostdemanding technical requirements.

Digital controlUNITROL F is a microprocessor-basedsystem and thus fully digital. It provideshigh control accuracy (min. ± 0.5 %) andhigh initial response (approx. 20 ms). Itswell-structured software offers a widerange of functions covering standard (e.g.limiters) and optional (e.g. PSS) functions.

Local operationUNITROL F includes a control panel forlocal operation and monitoring. With thispanel it is also possible to modify systemparameters and to make minor changes tothe application programs on-line.

The operation and monitoring of the sys-tem can also be performed via PC usingUNITROL F’s optional “Commissioning andMaintenance Tools” (CMT).

CommunicationUNITROL F can be provided with a serialcommunication line supporting differentprotocols for remote operational controland monitoring. This is in addition to a setof I/O interfaces which is required foroperation from control room. All I/O inter-faces are electrically separated by means ofrelays and opto couplers.

DiagnosticsUtilizing microprocessor technology pro-vides the user with comprehensive diag-nostics.

Troubleshooting is easily performed viathe control panel or by a PC using CMTsoftware tool.

System configurations (Fig. 1)AVR and SES are available in the followingconfigurations:

• Single automatic channel system (SFE)with one excitation module includingone power converter and one controllerfor both AUTO and MAN control modes

• Dual automatic channel system (AFT)with two identical excitation moduleseach with power converter and control-ler. Each channel can operate in AUTOor MAN mode.

A follow-up control ensures a smoothchange-over from one mode or one chan-nel to another.

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UNITROL® F System Configuration

RS485

iSBX

RS485

iSBX

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24 V

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ENTER

ACT PAR COMSELFUNC

REM

RESET R E FLOC

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UNITROL FR

AVR

SESFig. 2:Interfaces of theUNITROL F system,single and dual channelconfiguration

UNITROL F for staticexcitation systems(50 / 60 Hz supply)

UNITROL F forexcitation systems withrotating exciter usingpower converter eitherwith

1) IGB transistors forAC supply 16.6 to600 Hz and DCsupply

or

2) thyristors for ACsupply 50 / 60 Hz

or

thyristors for ACsupply upto 500 Hz

Voltageregulator

Panel

Channel IIChannel I

Voltageregulator

16 digitalinputs

16 digitaloutputs

16 digitalinputs

16 digitaloutputs

Connection toCH1 or CH2alternatively

Excitation

module

Excitation

module

110/220 VAC

24-48/110-250 VDC

AC Supply1- or 3phase16.6 to 500 Hzor DC

Electronics supply Dual channel option

analog2 in / 2 out

analog2 in / 2 out

Basic input/output Optional input/output

Dual channeloption

Voltageregulator

UNITROL® F Software Functionality

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A well-structured and stable softwarewith a wide range of function blocksenables users to tailor the system totheir own needs.

Functionality of the standardprogramThis comprises the following excitationfunctions:

Basic control functions

• Voltage regulator with PID filter(AUTO mode)

• Field current regulator with PI filter(MAN mode)

• Reactive and/or active current compen-sation

• Limiters for– maximum and minimum field current– maximum stator current (lead / lag)– underexcitation– Volts-per-Hertz

• Follow-up control– AUTO ↔ AUTO (for dual automatic

channel systems only)– AUTO ↔ MAN

• Power factor / reactive current regulation• Softstart function in AUTO mode• MANUAL restrict.

Optional control functions

• Power system stabilizer (IEEE - PSS2A).

Basic protection and monitoringfunctions

• Field flashing time• Overcurrent (instantaneous / inverse

time) protection• Loss of excitation protection• Converter temperature monitoring• Thyristor conduction monitoring• Potential transformer monitoring• Main supply undervoltage• Auxiliary supply undervoltage.

Optional protection and monitoringfunctions

• Rotating diodes monitoring• Rotor temperature (for SES only)• Volts per Hertz protection.

Monitoring and protection functions arecategorized in three different action levels:

• Alarm only

• Change-over to the second channel (ifprovided) to avoid unnecessary trips

• Instantaneous excitation trip for protec-tion purposes.

Logic control

For standard sequences and interlocksthere are fixed pre-programmed functionblocks.

Application function blocksBesides the functions available in thestandard program, there are additionalfunction blocks of different kind whichcan be used for the application program.Well proven optional application proce-dures such as I/O extension, specificmonitoring functions etc. are available.

Data recordingThe UNITROL F software also includes anevent logger which stores up to 100events and alarms with system’s timestamp. They can be recalled via the con-trol panel or the CMT software for eventanalysis.

Up to six different system measurementscan be stored in UNITROL F’s data log-ger. They can be displayed by the trend-ing window of the CMT software fordiagnostics.

Processor monitoring

Self test

After switching on the supply voltages ofthe control board, the processor starts aselftest program. During the initialization,both RAM and ROM (flash memories) aretested. The control board also monitorsthe different levels of power supply.

Watchdog function

The control board contains an internalWatchdog which monitors the programexecution.

UNITROL® F Additional Functions

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The functionality of the UNITROL Fsystem can easily be extended. Forsome of those functions an additionalhardware and software is required.

Power System Stabilizer (PSS)The purpose of the Power System Stabi-lizer is to use the generator excitation toimprove the damping of power swingsand the stability of the generator and thetransmission system as a whole. The PSSoperates by influencing the AVR’s input –most effective with a static excitationsystem, but also successful for systemswith rotating exciter (Fig. 3).

UNITROL F’s power system stabilizer isbased on IEEE PSS2A (i.e. with accelerat-ing power measuring).

A printed circuit board, which is pluggedin a connector and fixed on the measur-ing processing board, is required, in addi-tion to PSS software for the PSS functionin UNITROL F.

Supervision of rotating diodes

With this add-on component, open orshort circuits in the branches of the rotat-ing rectifier, used in brushless systems,can be detected selectively over a widerange of rotational speeds.

A filter of the 8th order, synchronized withthe rotational speed, measures the har-monics with the frequency of the excita-tion machine from the excitation currentsignal. Depending on the amplitude rela-tive to the excitation current, it is possibleto distinguish between an open and ashort circuit in the branch.

For this function a small printed circuitboard is required which is plugged in aconnector of the measuring processingboard.

Additional inputs/outputs

If additional digital inputs/outputs arerequired, an I/O extension for 16 inputand 16 output interfaces is available. Theextension consists of a printed circuitboard which will be piggy-pegged on themain board in the excitation module anda second I/O board which is mounted onthe frame in the cubicle.

With a second variant of the I/O exten-sion the voltage regulating system can beexpanded with another two analog in-puts/outputs.

Fig. 3:Response without(above) and with PSSfunction (below) at anexcitation system withrotating exciter for an1140 MVA generator(P = 860 MVA, setpointstep-change 5 %)

Fig. 4:Printed circuit boardsfor additional functions

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UNITROL® F Programming

Although UNITROL F equipment leaveour factory with the functionalityspecified by the customer, modifica-tion on system functionality can easilybe made later, if necessary.

Engineering tool GADGraphic Application Design (GAD) is a PCtool for application programming.This tool offers the following features:

• Programming of the standard and appli-cation program

• Graphical editor for creating and modi-fying program diagrams (Fig. 5)

• User controlled outlook for documents• Possibility to create new documentation

symbols.

Application programs made with GADhave to be downloaded to the excitationmodule with the Commissioning andMaintenance Tool CMT.

Programming with control panelOn-line changes to the standard or appli-cation programs can be made using thecontrol panel, where the following func-tions are available:

• Activating program• Connecting inputs and outputs of func-

tion blocks• Modifying function block connections• Adding or removing function blocks• Changing function block execution

order• Displaying parameters of function

blocks of the application program.

The software of UNITROL F comprisestwo parts: Standard program and applica-tion program.

Standard programOur standard program is installed in ev-ery excitation module. If a function in thisprogram is not required, it can be dis-abled by a parameter. However, eachsystem will be configured with particularparameters specific to the installation inour factory. The control panel or a CMTcan be used for enabling/disabling suchfunctions as well as modification of theparameters, on-line or off-line.

Application programFor certain applications it is necessary toextend the standard program. With thisso-called application programming, stan-dard program block connections can bechanged and different application func-tion blocks can be added.

Fig. 5:GAD display, segmentof an applicationprogram diagram

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UNITROL® F Commissioning and Maintenance

The “Commissioning and Mainte-nance Tool” CMT of UNITROL F is asoftware which can also be used forthe operation and monitoring of exci-tation systems.

Fig. 6:Trending window of theCMT/UNITROL F

Other displays

• Alarm logger displayThis display shows the last 99 events,alarms and fault signals in chronologi-cal order.

• System functionsThis display represents a copy of theservice control panel.

• Data logger displayThis display shows the latest triggereddata (six channels, 1000 data pointseach), updated in the data logger inchronological order.

Fig. 7:Application programdiagram of the CMTwith parameter display

Commissioning andMaintenance Tool (CMT)With this tool the user can perform on-line changes to the application programs,observe the system function and changeparameter values.

It also includes a control and status dis-play to be used for operating the systemand observing its status. This tool in-cludes further functions as described inthe following:

Trending display

With this window, up to six real-timeanalog signals can be shown in trendingform or to be recorded for later trendingdisplay (Fig. 6). The collection of measur-ing data can be subjected to an event(event driven). All signals available in thesystem can be selected for trending dis-play. The selection of each signal includ-ing all required parameters for scalingand offset are available in a very user-friendly environment. The window showstrend line diagrams.

Application program display

This window shows the function blockdiagram made with GAD (Fig. 7). Theuser can select and review the real-timevalues of selected points in this display.

Parameters and signals display

This display enables the user to observeparameters or signals in a tabular format.The user can modify parameters if re-quired. One feature is that the user canclassify each parameter or signal intoparameter or signal groups. Later, he canchoose selected groups and watch orchange parameters and signals allocatedto this group only.

We reserve the right to change in the interest of technical development.

UNITROL® F System Communication

SDCS COM

PC-CARDSNAT 608 CMT

ENTER

ACT PAR COMSELFUNC

REM

RESET R E FLOC

0I

UNITROL FR

ABB Switzerland Ltd.Static Excitation Systems, Voltage Regulatorsand Synchronizing EquipmentCH-5300 Turgi / SwitzerlandTelephone: +41 (0) 58 589 24 86Fax: +41 (0) 58 589 23 33Email: pes@ch.abb.comInternet: www.abb.com / unitrol 3B

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Panel bus

The panel bus is a serial link (MODBUSprotocol) based on RS485 signal level witha transfer rate of 9600 Baud. The bus isused to connect the control panel as wellas for the data transfer to the second exci-tation module of a dual-channel system,(see Fig. 8).

Optical link for commissioning andmaintenance

UNITROL F can also be connected throughan optical link to an optional PC with aninstalled “Commissioning and Mainte-nance Tool”. This enables a secure andfast communication to the excitation sys-tem. This feature allows utilization of allfunctions of CMT with a transfer speed of1.5 MBaud and enables operation of theexcitation system from the PC. To utilizethis feature, a PC-Card for a Laptop or aSNAT 608 CMT ISA board for desktop PCis required. The connection board, SDCS-COM, can be ordered separately, which isinstalled in the excitation module.

Serial communication to higherhierarchical control systems

Communication with a higher hierarchicalsystem (hereinafter called Master) is alsopossible. Protocols for that are MODBUS,MODBUS+ or Profibus. An extra busadaptor is required for each channel ofthe excitation system for connecting theMaster via RS485 multi-drop link. The linksupports six data words (16 bit each) ineither direction. For Master remote con-trol, two data words in either direction arerequired. The remaining data words caneasily be connected to any input andoutput signals by the user.

For internal data transfer, between thetwo channels and to the control panel,UNITROL F uses a serial communicationline.

To provide a fast and reliable link forthe CMT tool, the excitation module hasan optical link connection to the PC(option).

Several communication protocols withcorresponding bus adapters (options)are available for controlling and moni-toring UNITROL F from a higher hierar-chical control system.

Fig. 8:System communicationconnections

Channel 1 Channel 2

Controlpanel

DDCSopticallink

MasterRS 485 bus

Laptop orDesktop PC

Buscoupler

Buscoupler