ECS2100 ECA2bull

ECS2100 Digital Excitation System

ECA-2 10-08

ECS2100Excitation Control

Systems

FEATURES• Multi-Microprocessor based ECS2100 Digital Controller• +0.2% Voltage Regulation Accuracy• Performance response <20 ms• Redundant Controllers with Independent Supervisory Channel (options)• Six-SCR Power Rectifier Bridges Fixed and Drawer Type (options)• Multi-Bridge paralleling schemes up to 10,000 Adc• Patented Active Current Balance Algorithm• Multiple Excitation Limiters with on-line and off-line settings• Generator optimization by real-time limiter set point recalibration• Integrated Dual Input Power System Stabilizer IEEE Type 2 (optional)• Negative Field Forcing for highest system performance• Multiple Operating Modes with Auto-following• Multiple protection functions with on-line and off-line settings• Programmable input/output terminations• Programmable Sequencing provisions• Built-in Field Ground Protection (64F)• High Initial Response Per IEEE 421.2• Color Touch Screen for local and/or remote monitor and control• ccTools, a sophisticated software configuration program for setup and testing• Continuous self diagnostic capabilities• Transient event recording and data logging (options)• Incorporates fiber optics for critical signals• Provisions for Field Flashing from Station Service

P. O. BOX 269 HIGHLAND, ILLINOIS, U.S.A. 62249 PHONE 618-654-2341 FAX 618-654-2351

BACKGROUND,HISTORY,

PRODUCT DESCRIPTIONPage 2

FUNCTIONALDESCRIPTION

Pages 3 through 12

Control Channel OptionsPages 3 and 4

System OperationPage 5

Hardware/SoftwarePages 6 and 7

Software ControlPages 7 and 8

Limiters and ProtectionPages 8 through 10

Monitoring FunctionsPage 10

Power SectionPages 10 and 11

Control and MaintenancePages 11 and 12

APPLICATIONBasler Electric has expanded its excitation product offering with the addition of theECS2100 excitation control system. The ECS2100 is a multi-microprocessorexcitation control system that provides advanced technology to precisely control,protect, and monitor synchronous generators, including new and existing applica-tions that are driven by all types of prime movers, such as steam, gas, hydro, anddiesel. Its multifunctional design allows the ECS2100 to operate as a voltageregulator or as a static exciter, providing excitation currents up to 10,000 Adc. Sincethe introduction of the ECS2100, it has been successfully applied to generatorsranging from 1 to 1300 MW.


BackgroundType ECS2100 static excitation control systems haveevolved from years of experience that originated withthe original Westinghouse Distribution & Controlsgroup. Under Westinghouse, many products datingback into the 1920’s were developed for the generatorexcitation market. In 1994, Cutler-Hammer purchasedthe Distribution & Controls business from Westinghouseand carried the tradition and expertise to support thissame market. In June of 2006, Basler Electric acquiredCutler-Hammer’s Excitation Control product line tocomplement Basler’s existing DECS product offering.Basler Electric has been committed to the generatorexcitation market since the mid 1960’s and is dedicatedto support this continued effort.

Product HistoryAs part of the acquisition, Basler Electric inherited asubstantial amount of history dating back to the 1920’sthat is associated with the original Westinghouseexcitation products line. The following provides a briefhistorical description of the Westinghouse and Cutler-Hammer excitation system now in service in manypower plants.

MGR (Introduced in the late 1980’s)The MGR (Medium Generator Regulator) was an analogstatic excitation and voltage regulating systems thatcovered small and medium size generators in utility,cogeneration, industrial and hydro applications. TheMGR was designed as a replacement for existing

DESCRIPTION

The Basler ECS2100 Digital Excitation System isdesigned to provide digital voltage regulation, control,protection, and monitoring functions for a synchronousgenerator. The ECS2100 Digital Excitation System is amultiple microprocessor-based control system. ECS2100uses a digital signal processor for required computa-tional speed of advanced control functions and algo-rithms and an integrated 32-bit communications control-ler for implementation of event recording, data logging,and communications to external control systems and toa user-friendly PC interface for maintenance and analysisfunctions. The ECS2100 can be scaled to generationunits of all sizes with minimal changes except to thepower electronics and the excitation power potentialtransformer. A software tool, ccTool, is used to changesettings for the various limiting and protection functions,download new system firmware, and retrieve diagnosticsinformation.

2

BASLER DIGITAL EXCITATION SYSTEMS - Type ECS2100

Westinghouse voltage regulators and other manufactur-ers' single field regulators. Typically, the MGR providedexcitation levels up to 600 Adc. As an update to theMGR, Basler can provide a “Front End” Digital solutionthat utilizes our DECS-400 Digital Excitation ControlSystem. This digital upgrade uses many of the existingcomponents of the MGR, but it adds many new featuresand functions. Contact Basler Electric for more detailsor download the DECS-400 product bulletin (SZF) fromwww.basler.com.

WTA-300B (Introduced in the mid 1990’s)The WTA-300B (Westinghouse Trinastat Amplifier), is thelatest of the WTA family of solid-state analog staticexciter/voltage regulators which were standard equip-ment on large utility and industrial generators typicallysized greater than 100,000 kVA. The first WTAs wereintroduced in the mid 1960’s. Typically, the WTA-300Bwas utilized for excitation currents greater than 500 Adc.

WDR-2000 (Introduced in the early 1990’s)The WDR-2000 (Westinghouse Digital Regulator) wasWestinghouse’s first microprocessor designed excitationsystem. Primarily, it was applied on medium to largegenerators requiring 1000 to 10,000 Adc of excitation.Today, the WDR-2000 can be retrofitted with the latesttechnology by replacing the WDR rack module with adrop-in ECS-RW. The ECS-RW provides advancedcommunication capabilities and many of the samefeatures and functions as specified in this product

bulletin. Contact Basler Electric for more details.

The Basler system consists of one or more thyristorpower converters, each with its own digital firing con-trol. A single converter or multiple converters operatewith single-channel or multi-channel control logic forincreased reliability. Operator control can be providedthrough a single-cable interconnection to a local and/orremote PanelMate operator panel, interface to PLC,SCADA, or plant DCS (Distributed Control System), ortraditional discrete switches and meters.

Power to the ECS2100 can be supplied via a powerpotential transformer (PPT) from the generator terminals.A field flashing option will be added for black start whenthe generator terminals are used for the excitation powersource. Alternately, power to the ECS2100 DigitalExcitation System can be taken from a reliable three-phase, 50 or 60 Hz station auxiliary source.

http://www.basler.com


Figure 1 - Typical Dual Channel Two Power Drawer ECS2100 with Breaker and Auxiliary Cubicle

3

STANDARD SYSTEM FUNCTIONAL DESCRIPTION

General

The design of the ECS2100 Digital Excitation Systempermits flexibility in the system architecture that is the mostappropriate for your application. Proposed configurationsinclude a single-channel system and alternates for a dual-channel or three-channel system with each type of systemcapable of using redundant power converters. A typicalcontrol channel consists of microprocessor-based modulesfor digital sensing, regulation, SCR firing control andsequence control algorithms. The cabinet lineup includes alogic cabinet and the required number of cabinets for thepower converters and auxiliary devices (See Fig. 1). Itshould be noted that not all items will be utilized in allapplications; therefore, some components may only beapplicable to certain applications. It is recommended todiscuss options with respect to the application with BaslerElectric's Applications Specialists.

CONTROL CHANNEL OPTIONS

Single-Control Channel SystemThe Single-Control Channel System is the most basicconfiguration in the ECS2100 line. The regulator automaticand manual controls with associated limiter, protection,sequence control, and firing control are implemented on oneset of printed circuit modules. The control channel includes

the Excitation Control Module (ECM), Firing Control Inter-face Module (FCIM), and Sensor Input Module (SIM). Thecontrol channel interfaces through fiber optic cable to thefiring control (Bridge Control Module) of one or morethyristor power converters. Redundant internal powersupplies provide power for the single control channel. Eachpower converter is equipped with its own Bridge ControlModule (BCM) that provides digital firing pulses to fire thebridge (See Figs 2 and 5).

Figure 2 - ECS2100 One-Line Diagram,Single Channel Control Scheme


FUNCTIONAL DESCRIPTION, continued

4

CONTROL CHANNEL OPTIONS, continued

Dual-Control Channel SystemThe dual-channel capability of the ECS2100 Digital ExcitationSystem is configured with two identical sets of printed circuitmodules. Each of the two sets has the capability of performingthe voltage regulation, limiter, protection, sequence control,and firing functions. Both sets are connected to control the firingtime of a Bridge Control Module (BCM) associated with its ownpower converter bridge. Signals from both control channels aresent to each BCM. Each BCM has a state-select contact thatdetermines which channel controls the BCM. The systeminitially is set up such that the main channel controls the BCM.Should the internal diagnostics in the main channel detect afailure, an external relay will be energized, which in turn willdirect the BCM to ignore the control signal from the otherchannel. A remote switch may be used to transfer control fromthe main to redundant channel for maintenance (See Fig 3).

Dual-Control Channel with SupervisionA dual-channel configuration with a third supervisory channelis available for additional reliability for protection of the genera-tor.

The three-channel system consists of the dual-channel configu-ration plus a third channel that supervises the other two. Allthree channels monitor limiting and protection functions. Whenconditions call for a unit trip, the combined logic of the threecontrollers using two-of-three voting logic determines when theunit is tripped. This two-out-of-three voting process with thethird channel (Supervisory) is also used to determine which ofthe dual channel controllers is selected to be in control andregulate the generator's output.

Figure 3 - ECS2100 One-Line Diagram,Dual Channel Control Scheme

Power Converter AssemblyThe power converters use thyristors in a three-phase fullconverter bridge configuration. This configurationapplies positive and negative forcing voltage to thegenerator field for dual-directional forcing of fieldvoltage. The field current, however, cannot be reversed.The thyristors conduct current once each cycle at avariable angle in the cycle as determined by theamplified error signal from the regulator. The earlier inthe cycle that the thyristors conduct, the greater theamount of energy delivered to the field. Thus, theregulator controls excitation by varying the output of thepower amplifiers by controlling the time of the firingpulses. Each power converter is equipped with conduc-tion monitoring and thyristor overtemperature protection.

The power converters will be supplied in adjacentcubicles as required for the application. The powerconverter section features either drawout thyristorbridges or fixed bridge assemblies.

The power converter features a compact design. If op-tional power converter redundancy is purchased withdrawout power converters, the converters may be isola-ted under full load. Redundant power converters can beadded to both single and dual-channel configurations.

With drawout converters, the power section features aforced air-cooling system with a main fan and a backupspare fan for each power cubicle. The fan controlcircuits including automatic transfer to the backup fanare grouped together in one convenient location in eachpower cubicle. With fixed bridge assemblies, the coolingcan be either convection or forced.

Active Current BalanceThe patented active current balancing algorithms(known as "Skip Firing") may be provided in multi-bridgeschemes. By monitoring the temperature of each SCR inthe Power Converter, this special algorithm facilitates anelectronic method for rectifier bridge current sharing.This unique approach allows excitation currents toreach up to 10,000 Adc continuously.

Figure 4 - 1100 Adc Power Drawer



5

SYSTEM OPERATIONThe ECS2100 Digital Excitation System for a static exciterincludes the ECS2100 Digital Voltage Regulator for auto-matic and manual control. In the automatic mode, the digitalregulator controls generator terminal voltage by supplying adigital control signal to the firing circuits. The bridge controlmodule (BCM) generates firing pulses for the power amplifi-ers in response to the ac regulator signal so as to control thepower amplifier output current. In the manual mode, the dcfield current regulator controls the system by sending asignal through the firing circuits to control the output currentof the power amplifiers.

Regulation ModesA variety of feedback control functions can be implemented.The purpose of these functions is to hold the particularregulated quantity at a set point. The set point is adjustableby operator action. The regulator gain, range of the set point,and the slew rate of the set point are adjustable for allregulators. Transient gain reduction is included with eachregulator channel for the static exciter application. Anotherfeedback control function is an Excitation System Stabilizer.This method is typically used in rotary exciter applications.In addition, a Proportional, Integral, and Derivative (PID) typecontroller is also available.

Each regulator has its own adjuster to provide a referencesignal for that regulator. The slew rate, which can be set bythe operator, is adjustable between minimum and maximumset points. The minimum and maximum set points can varyfrom 1 to over 200 seconds. The set point adjusters haveposition indication capability. There are 5 regulation modesof operation that can utilize the various feedback controlfunctions.

Automatic Voltage Regulation ModeIn Automatic Voltage Regulation mode, the ECS2100maintains the generator's voltage to <0.2% of the setpoint from no load to full load of the generator. Thegenerator voltage adjustment range is 40 to 110% ofnominal.Manual Regulation Mode - Generator Field CurrentWhen the system is in the Manual Regulation-GeneratorField Current mode, generator field current is regulatedby the ECS2100 to within ±0.5% of the generator noload field current. The adjustment range is 20% to 125%of the generator full load rated field current.Manual Regulation Mode - Generator Field VoltageWhen the system is in the Manual Regulation-GeneratorField Voltage mode, generator field voltage is held towithin ±0.5% of the generator no load field voltage. Theadjustment range is from 20% to 125% of the generatorfull load field voltage.VAR Control ModeIn VAR Control mode, the system maintains the averageVAR output of the generators output to an adjustabledead band setting (0.5%-10% or rated generator MVA).The time delay is adjustable from 0.02 to 10 seconds.The adjustment range of the VAR's set point is between100% Overexcited to 100% Underexcited.

Power Factor Control ModeIn Power Factor (PF) Control mode, the system holds theaverage power factor within an adjustable deadband of0.01-0.1 PF with a delay of 0.02-10 seconds as thegenerator load changes. Below an adjustable set pointor when the voltage is outside a settable range, thepower factor controller is automatically turned off andthe system functions as an automatic or manual regula-tor. The range of adjustment is from 10 percent to 100percent load. The range over which the power factor canbe controlled is adjustable between 0.1 PF lead and0.1 PF lag.

Operating Mode Set Point FollowersThe Set point Followers function provides a virtuallybumpless change in the newly regulated quantity when atransfer is made from automatic voltage regulation tomanual regulation and from manual regulation to automaticregulation under steady conditions. The bandwidth betweenthe controlling regulator-firing command and the followingregulator firing command is adjustable from 0.1 percent tomore than 10 percent. The time delay during which thatbandwidth can be exceeded is adjustable from .02 to morethan 10 seconds. During transients, the transfer may bemade from one regulator to a second one even if thattransfer will result in a bump.

The var/power factor controller takes raise or lower signalsand generates the referenced set point for the automatic var/power factor regulator. The adjuster followers (whenenabled) operate to raise or lower this reference set pointuntil the difference between the automatic voltage regulatorand automatic var/power factor regulator error signals iswithin a desired deadband. If that signal is outside thedeadband for longer than an adjustable deadband delay inseconds, a raise or lower output is activated. The outputremains activated until the balance signal returns to withinthe deadband value.

Programmable Sequence Control (PSC)Programmable Sequence Control is the function thatperforms startup, running, and shutdown control of theECS2100 Digital Excitation System. The function is imple-mented in the software of the ECM. All control is provided inPSC. When the power requirements of the devices beingoperated, such as the 41A device, require them or when acustomer interface requires dry contacts, discrete relays areadded.

Programmable Sequence Control is made up of a series oflogic blocks or gates that can be constructed using ccTool.Sequence control is displayed in ladder logic or ladderdiagram fashion using ccTool.



6

HARDWARE AND SOFTWARE FEATURE DESCRIPTION

Digital Voltage Regulator Channel Control Logic(Hardware)

Excitation Control Module (ECM)The Excitation Control Module (ECM) is the central controlcard in a control channel for the excitation control system.

The ECM contains the intelligence to implement all of theregulators, limiters, protection, communication, and systemcontrol functions.

Each system utilizes one ECM module per channel. Thefunction of a module as a main controller or a redundantcontroller is selectable in the software in its microproces-sors. Each module contains the hardware needed toimplement the software functions/settings and is stored innonvolatile flash memory.

The ECM board has the capability to synchronize the systemclock with an Arbiter Systems 1084B GPS satellite clock.Currently, the software is capable of synchronizing thecontroller clock to within 1ms of the satellite clock. Thesystem has been designed to allow the GPS satellite clocksignal to be brought in to the ECM board through the serialport (RS-232 DB-9 pin connection or RS-485 port).

Firing Control Interface Module (FCIM)The Firing Control Interface Module (FCIM) is the interfacebetween each Bridge Control Module (BCM) and the ExciterControl Module (ECM). See Fig. 5. The FCIM receives afiring command signal from the ECM and signals from FieldIsolation Transducers (FIT) for field voltage and the excita-tion transformer (PPT) secondary voltage. Based on thisinformation, the FCIM supervises the firing control for asingle bridge or multiple thyristor-controlled bridges. Themodule receives information regarding bridge status fromeach BCM. The FCIM indicates loss of any one thyristor, abridge low temperature alarm, and a bridge high tempera-ture alarm. The FCIM also responds to phase-up, phase-back, and turn-off-pulse commands.

Sensor Input Module (SIM)The Sensor Input Module (SIM) has high-speed analoginputs that collect data from regulation and meteringpotential transformers and current transformers connected tothe generator's output, as well as other analog signals. TheSIM receives signals from transformers that isolate it fromanalog inputs. The PT signals can be in the range of 20 to160 Vrms. The CT signals are converted to a voltagethrough a 0.3 ohm resistor yielding voltages in the range of0 to 1.8 Vrms. The input frequency can vary in the range of20 to 70 Hz. The continuous line current can be in the rangeof 0.1 to 6 A in the CT secondary. During faults, transitsignals as high as 25 A can be sensed without clipping.

The SIM contains 12 analog-to-digital converters for makingmeasurements from these transformers and other inputs.Each analog-to-digital converter has a 12-bit resolution. Thehigh-speed analog inputs sample the incoming signalssimultaneously and are updated every millisecond.

Figure 5 - Typical Single Channel Control Scheme

The SIM is also the controller for serial input/output links tothe ECM. Fiber optic connections are made from the SIM toexpansion low-speed analog (AIOM) and digital (DIOM)input/output modules.

Digital I/O Module (DIOM)The purpose of the Digital Input / Output Module (DIOM) is toprovide a means to interface the ECS2100 excitation controlsystem with external devices. Each DIOM has the capabilityto sense twelve digital inputs (±24 - 125Vdc or 120Vdc)which are sampled every 8 ms. These inputs are commonlyused to provide an interface to the excitation control systemfrom pushbuttons, control switches, and relay auxiliarycontacts.

Eight digital form C relay outputs are also provided on eachmodule. The digital outputs are each connected to form Crelays with ratings of 10A, 120Vac or 10A, 30Vdc. The ECMupdates the outputs at an 8 ms rate. These outputs arecommonly used to drive external relays and indicator lights,or to interface with DCS's and PLC's. Each ECS2100 controlchannel may be equipped with a maximum of four DIOMsthat are connected in daisy chain fashion using an isolatedbi-directional fiber optic communication link. Utilizing theccTool software, the digital input and output data can beconnected to any control software block input or output inthe ECM.

These may be included in the original system or may beadded by the customer in the field as the need for additionalI/O arises. Because the fiber optic link is immune to electri-cal noise, the boards may be mounted in close proximity orup to 22 meters from the cubicle. This results in reducedwiring to the excitation cubicle.

Analog I/O Module (AIOM)The purpose of the Analog Input / Output Module (AIOM) isto provide a means to interface the ECS2100 excitationcontrol system with external devices such as meters,resistance thermal devices (RTD), transducers, chartrecorders, distributed control systems (DCS), and program-mable logic controllers (PLC). Each AIOM has the capabilityto sense two analog inputs (±10 Vdc) that could be used tointerface the ECS2100 to PLC's or DCS systems. The AIOM


7


also has one 100 ohm Platinum RTD input that is commonlyused to provide temperature and hydrogen gas pressurefeedback to the system for use in the generator optimizationfunctions associated with compensated excitation limiting.

The AIOM provides four individually configurable (±10 Vdc /4-20 mAdc) analog outputs on each module with 16 bitresolution. Each ECS2100 control channel may beequipped with a maximum of four AIOMs that are connectedin daisy chain fashion using an isolated bi-directional fiberoptic communication link. These outputs are commonly usedto drive existing panel meters or to interface with DCSsystems or chart recorders. Utilizing the ccTool software, theanalog input and output data can be connected to anycontrol software block input or output in the ECM. Becausethe fiber optic link is immune to electrical noise, the boardsmay be mounted in close proximity or up to 22 meters fromthe cubicle. This results in reduced wiring to the excitationcubicle.

Power Supplies Dual SourceThe excitation system can operate under extreme ranges ofsupply voltage. The Digital Excitation System contains dual-source power supplies that provide reliable control powerfrom both the 120 Vac excitation source and the 125 Vbattery. Thus, control power is available regardless ofmachine speed or terminal voltage.

A dc-dc converter will be supplied for applications where a250 Vdc supply voltage is used. dc control power is takenfrom both the customer's 125 V or 250 Vdc source andauctioneered with rectified 125 Vdc from 120 V, single-phase ac taken from the secondary of the excitation trans-former.

Generator Field Ground DetectionA ground in the field of a synchronous machine should bedetected since the occurrence of a second ground mightshort circuit part of the field winding, and the resultantunbalance and vibration may damage the machine.

The function of the exciter ground detector panel is to detecta ground current flowing from the machine dc field windingto the grounded machine shaft. The ground detector con-tinuously monitors the machine field and detects groundcurrents ranging from 0.1 mA to 15 mA. A remote alarm isavailable for annunciation whenever a ground is detected.Provision is also made for checking the operation of theground current sensing circuitry by applying a "simulatedground" to the PC card. The ground detector panel may beapplied to brush excitation systems at rated generator fieldvoltages up to 1,250 Vdc.

Rapid De-ExcitationA dc field breaker is not required with the ECS2100. Con-sequently, there is no need for a field discharge resistor ordc field breaker. An ac supply contactor or drawout circuitbreaker, electrically operated with six (6) auxiliary contacts,will be supplied. The exciter power amplifier is a full con-verter (with thyristors in all legs of the three-phase bridge)with the ability to force down excitation quickly. The field isde-excited by phasing back the firing pulses to the static

exciter amplifier. This action causes stored energy in thefield to be inverted back to the source, which quicklyreduces the field excitation to zero. Upon opening the acfield contactor, the remaining field energy will be dissipatedvery rapidly in a nonlinear resistor permanently connectedacross the field. Under emergencies when the ac fieldcontactor is opened without de-exciting the field, the fieldcurrent is discharged through the last two conductingthyristors or the nonlinear resistor.

In larger static excitation systems, rapid de-excitation isaccomplished by a combination of electronically invertingthe field voltage and triggering the DX module that shorts thefield through a discharge resistor. The energy stored in thefield is dissipated quickly in the discharge resistor thatreduces the field excitation to zero. The ac field breaker isthen opened to complete the shutdown.

De-excitation Module (DX)The DX module is a thyristor-controlled circuit that providesan alternate path for the generator field current when thenormal path is not available. The normal path is through thePPT, 41A-supply breaker, and the generator field. Shouldthis path be interrupted, the DX circuit provides the safealternate path to dissipate the field energy. To provide thealternate path, the DX thyristor is triggered by a controlsignal and/or excessive negative field voltage.

Control firing of the thyristor is implemented when theexcitation system provides a de-excitation signal, typicallywhen device 41A, the ac supply breaker, is opened. Voltagefiring triggers the thyristor when the field voltage exceeds apreset negative voltage value. Feedback to the excitationsystem is provided when current is present in the DXmodule. A current sensing circuit in the module provides alogic signal to the excitation system whenever the current inthe DX exceeds a minimum preset level.

Crowbar Module (CB)The Crowbar module (CB) protects the generator field andexciter power converter from excessive high positive fieldvoltages. Generator pole slip is a source of positive highvoltage. The Crowbar self-triggers any time a high voltageoccurs. The system automatically recovers once the voltagestarts to go negative.

Since the power converter thyristors are likely to be phasedon when the Crowbar operates, a resistor is placed in serieswith the module to limit the bridge current and provide apole-slip current path. Feedback to the excitation system isprovided when current is present in the Crowbar.

Field Flashing (Optional)Field flashing is required when the static exciter receives allof its energy supply from the machine terminals and themachine terminal voltage is zero at startup. It is necessary toflash the machine field to raise the machine terminal voltageto a suitable level that is sufficient for the static exciter tobegin to build up the machine voltage.



8

In order to ensure positive buildup of the ac generatorvoltage on startup, a reliable dc source of power is requiredfor momentary field flashing. This source of power is appliedmomentarily to the generator field during startup by means ofcontacts on the field flash contactor. Field flashing after thea-c contactor closes by automatic or manual implementation,which may be supplied as an option. The field flash contactorhas a momentary action and is supplied as standardequipment. In manual if the operator releases the switch, themomentary action permits the field to be disconnected fromthe dc source. The field flashing circuit includes a timer toprevent overflashing the field and a phase-up circuit thatminimizes the load on the station battery source. The fieldflash is turned off when either the terminal voltage builds upor the field current exceeds a settable minimum value. Therange of settings is from 1 percent to 100 percent of no-loadfield current.

Optionally, an ac, single-phase field-flashing source can beused. In that case a rectifier circuit is added to the assembly.

SOFTWARE CONTROL FUNCTIONS

Reactive CompensationReactive compensation, either droop or rise, is included withthe ECS2100 system. These functions modify generatorvoltage by regulator action to compensate for the impedancedrop from the machine terminals to a fixed point in thesystem. Action is accomplished by inserting into the regulatora reference voltage equivalent to the settable impedancedrop time's reactive current. Three types of reactive compen-sation are available with the ECS2100.

• Generator Reactive Current Compensation - Using One Set ofCTs

• Generator Cross-Current Compensation - Using Two Sets ofCTs (Optional)

• Line Drop Compensation Using a Line CT - Responds to bothResistive and Reactive currents (Optional)

Power System Stabilizer (Optional)The Power System Stabilizer (PSS) provides a supplemen-tary control signal input to a synchronous machine voltageregulator that improves system dynamic performance. Thestabilizing signal provides positive damping of the electro-mechanical oscillations that occur as a result of systemdisturbances. Without supplementary control, a continuouslyacting voltage regulator can contribute negative damping tosystem swings, and these oscillations may be sustained ormay even increase in amplitude.

The ECS2100 has only one predefined PSS algorithm.Implementation of the IEEE Type 2 "Integral of AcceleratingPower" Dual Input PSS (power and frequency) power systemstabilizer model PSS is standard. The function produces astabilizing signal derived from two inputs: the deviation insynchronous machine speed and electrical power. Thepolarity of the signal is in the direction to increase excitationfor terminal frequency deviations above normal frequency.This dual input PSS includes a ramp-tracking filter: one ortwo stages of high pass (washout) filters, and two or threelead-lag stages. Ramping output limiters are included to

minimize the adverse effects of the PSS on system voltage.The Type 2 PSS requires inputs from three line CTs toachieve the best accuracy. The PSS also incorporates a lowpower threshold and will automatically disable the PSSfunction when the generators power drop below a predeter-mined level.

LIMITERSThe purpose of limiters is to take away control from any of theregulators, either manual or auto, then regulate the particularquantity at the pickup point of the limiter. The limiters providean alternate feedback control loop to the regulators, andeach limiter is provided with its own adjustable gain, adjust-able transient gain reduction, or damping algorithm asneeded to provide stable loop operation when the limiter isin control. Limiters operate whether the unit is in automatic ormanual regulation modes.

All limiters have alarms associated with them. The first alarmis generated when the pickup has been exceeded. A secondalarm, for limiters with time delays, is generated after thelimiter has timed out. A third alarm is generated when thelimiter has taken control from the regulator.

Minimum Excitation Limiter- Steady State Stability Limit(MEL)The Minimum Excitation Limiter (MEL) is based on generatorstability. The limiter keeps the operating point of the genera-tor within adjustable MW and Mvar curves. The operatingcurve, in terms of MW and Mvar will vary proportionally to thesquare of the generator terminal voltage. The shape of theMW and Mvar operating curves is constructed in a piece-wise-linear fashion made up of five straight-line segments.Both Summing Point and Takeover style limiter is availablewith the MEL.

Under Excitation Limiter- Generator Capability Curve(UEL) - OptionalThe Under Excitation Limiter (UEL) prevents excitationreduction in the ac generator to levels that would result indamage to the generator while it is operating in anunderexcited mode. The UEL is based on the generatorcapability curve. The limiter keeps the operating point of thegenerator within adjustable MW and Mvar curves. Theshapes of the MW and Mvar operating curves are con-structed in a piecewise-linear fashion made up of fivestraight-line segments. The inputs to the limiter are takenfrom machine potential and current transformers. The limiteroutput auctioneers against the voltage sensing signal outputin an auctioneering function for control of the power amplifi-ers. The control of the power amplifiers by the limiter pre-vents the auto or manual regulator elements from decreasingmachine excitation to levels below the desired set character-istic value. Both Suming Point and Takeover style limiter isavailable with the UEL.

Note: The following pickup modification (recalibrationfunctions are available as options to the UEL:



9

Hydrogen Gas Pressure Recalibration for UEL (Optional)Hydrogen Gas Pressure Recalibration modifies the UELoperating curve. The curve varies as a function of thegenerator hydrogen pressure and is reduced as thehydrogen pressure is reduced. The system receives eithera 4-20 mA signal or a ±10 V signal.Temperature Recalibration for UEL (Optional)Temperature Recalibration modifies the UEL operatingcurve. The modified curve varies as a function of thegenerator temperature measured by an RTD. The curve isproportional to the temperature.

Over Excitation Limiter (OEL)The Over Excitation Limiter (OEL) acts through the regulatorto return the value of excitation to a preset value afteran adjustable time delay during which overexcitation ispermitted for field forcing. The limiter operates on aninverse time characteristic that permits lower values ofoverexcitation for longer time intervals and limits highervalues of over-excitation for shorter time intervals. Thislimiter's output auctioneers with the output of theauctioneering function in a signal mixer such that reducedexcitation is sent to the firing circuit. The Over ExcitationLimiter keeps the generator field current or voltage below adesired value of field voltage or field current that isadjustable. This limiter functions with the InstantaneousLimiter to provide a two step operation. The first operationis the instantaneous limiter. The second operation is thetime-delayed limiter.

The OEL provides a "memory" of the time-dependent natureof the residual and cumulative effects of rotor heating. If thefield quantity drops below the inverse limiter pickup, theinverse timer immediately begins to reduce the accumulatedtime over pickup to zero with a cool-down characteristiccurve. An alarm is indicated when the limiter picks up.

Note: The following pickup modification (recalibration)functions are available as options to the Over ExcitationLimiter:

Hydrogen Gas Pressure Recalibration for OEL (Optional)The Hydrogen Gas Pressure Recalibration functionmodifies the pickup point of the inverse delay portion ofthe OEL. The pickup point varies as a function of thegenerator hydrogen pressure. The curve is proportional tothe absolute pressure. The proportionality constant isadjustable. The system can receive either a 4-20 mAsignal or a ±10-20 mA signal or a ±10 V signal.Temperature Recalibration for OEL (Optional)Temperature Recalibration modifies the OEL operatingcurve. The modified curve will vary as a function of thegenerator temperature measured by a 100-ohm RTD. Thecurve is proportional to the temperature. If a thermocoupleor another size RTD is used, a separate transducer witheither a 4-20 mA output or ±10 V signals is required.Instantaneous Field Current LimiterThe Instantaneous Field Current Limiter keeps thegenerator field current or voltage below a desired level.That level may correspond to a ceiling limit for the genera-

tor field voltage in a brushless excitation system, to theinstantaneous current limit of a thyristor bridge, or to a lowlevel of current required during startup operation. Theinstantaneous limiter setting is automatically changedbased on the status of the generator 52 breaker. When the52 breaker is open and the unit is off line, the instanta-neous limiter has an adjustable setting. When the 52breaker is closed and the unit is on line, the instantaneouslimiter has a second adjustable setting and a shortadjustable delay.Volts/Hertz Limiter (HXL)The Volts/Hertz Limiter keeps the ratio of generatorterminal voltage to line frequency below a desired value.The limiter is applied to the excitation system when thestation must operate under adverse circumstances withthe system frequency below normal operating range. Insuch cases, the reason for operating at reduced voltageduring under-frequency conditions is to avoid the heatingeffects of excessive magnetic flux in the generator,transformers, or other magnetic devices. The limiter usesan inverse curve that coordinates with the sample volts/Hertz curves shown in ANSI C37.102. The input to thevolts/Hertz limiter is machine terminal voltage, and itsoutput is a signal that auctioneers with the positiveauctioneering output signal in the signal mixer in such amanner that whichever signal that reduces excitation issent to the firing circuit.Generator Overvoltage Limiter (OVL)When the Generator Overvoltage Limiter is in control, thegenerator voltage is regulated to a pickup point below adesired line voltage. The limiter uses a selectable fixedtime delay.Generator Line Current Limiter (Optional)The Generator Line Current Limiter keeps the generatorline current below a desired level. The limiter is disabledwhen the power factor is near unity between 0.99 PF lagand 0.99 PF lead. The limiter is bidirectional. When thegenerator is operating overexcited, this limiter reduces thefield current. When the generator is operatingunderexcited, the limiter raises the field current. Theoperation of the limiter occurs following a fixed time delayafter the current has exceeded the pickup point. When thelimiter is operating, it regulates the generator line currentto within ±1.0% provided that the power factor is eitherless than 0.99 pf lead or less than 0.99 PF lag.Hydrogen Gas Pressure Recalibration for GeneratorLine Current Limiter (Optional)Hydrogen Gas Pressure Recalibration modifies the LineCurrent Limiter operating curve. The curve will be variedas a function of the generator hydrogen pressure and isreduced as the hydrogen pressure is being reduced. Thesystem receives either a 4-20 mA signal or a ±10 Vsignal.

PROTECTIONProtection functions operate whether in manual or auto.These functions provide alarm indications or trip commandswhen they operate. Protection functions do not tend toregulate or limit the signal, although some of them may



10

phase back the power bridges. For every Limiting Function,there is an associated Protection Function. The protectionelements are intended to back up the Limiting Functions inan effort to take control and attempt to avoid a system trip.

MONITORING FUNCTIONS via Color Touch ScreenThe monitoring functions include a variety of items that aredetermined by the inputs to the control modules. Values canbe displayed on a color touch screen locally and/or re-motely, if included. An alarm is generated whenever one ofthe monitored quantities exceeds an adjustable value.

Field Values - Displays field current, field voltage, andbalance signal associated with the operating modes/channels.Generator Field Temperature Monitor - Monitors anddisplays the rotor temperature. There are two levels ofalarm, low and high. An alarm is generated when eithertemperature exceeds a time delay.Generator Megawatts and MegavarsDisplays Generator Megawatts and Megavars functiondetermines the real and reactive power output of thegenerator for display. These values are available whetherone, two, or three CT signal(s) are utilized once pro-grammed.

Analog Signal Outputs Using AIO Module (Meter Drivers)The Analog Signal Outputs function sends an equivalentanalog signal to a meter or chart recorder. As a minimum,the following signals are selectable to send to the analogoutputs termination point: generator or exciter field current,generator or exciter field voltage, terminal voltage, terminalvoltage deviation, line frequency, line frequency deviation,line current, generator real power, generator reactive power,accelerating power, PPT voltage on static systems, any errordetector output, any set point adjuster signal, any limiteroutput, a firing command, any field temperature, the powersystem stabilizer output, or the balance meter output. Theuser can select the analog output channel for any of thequantities. The output range is ±10 V or 4 to 20 mA.

Alarm Outputs Using DIO ModuleA variety of alarm indications is available. The individualalarms can be indicated on the ccTool screen at the remoteor local personal computer. An alarm (exciter trouble) relayis available to indicate that an alarm has occurred. Up tothree additional individual relay contacts are available forannunciation.

Excitation Transformer Temperature Monitor Using a DIOModule - (Optional)The Excitation Transformer Temperature Monitor monitorsthe dry contacts of the temperature alarm of the excitationtransformer coils. An alarm is generated if the temperatureexceeds an adjustable value.

Alarms Displayed on CCToolsThese alarms are documented functions viewed throughLevel 1 of the ccTool program. The purpose of this is todetect an internal problem or fault in the ECS2100 system. Ifthe problem is non-critical, an alarm is generated and ashort description of the fault is displayed. If the problem iscritical, the main controller either automatically transferscontrol to another ECM, if present and prior to tripping theunit, or it trips the unit if no backup controller is available. Acritical problem is one that may result in tripping the turbine-generator off line or, if left uncorrected, could result indamage to the turbine-generator unit. All other problems willbe defined as non-critical.

POWER SECTION DESCRIPTION

Digital Firing LogicDigital firing control of the thyristor bridges in the ECS2100utilizes field programmable gate arrays that are supervisedby a microprocessor located on each Bridge Control Module(BCM). A separate microprocessor on the Firing ControlInterface Module (FCIM) controls all of the Bridge ControlModules (BCM). The use of a microprocessor at each bridgeprovides bridge intelligence and diagnostics at eachindividual bridge. The use of an FCIM permits simultaneousfiring of multiple bridges.

The ac error signal feeds a PID controller in the ECM and isthen sent to the microprocessors in the FCIM of the digitalfiring circuits, and the resultant timing command, then, issent to the field programmable gate arrays in the BCM.Then, the BCIM initiates the pulses being sent to thethyristors of the power converters. Each power converter is athree-phase, six-pulse, thyristor-controlled full converterwhose ac input line frequency can be in the range of 20 to480 Hz. The firing circuits are synchronized with the acsupply voltage and the associated thyristors or Silicon-Controlled Rectifiers (SCR). A linear relationship is estab-lished in a firing circuit between the regulator output signalvoltage and the dc output voltage of the associated powerconverter.

Thyristor Bridge ControlThe bridge control function supports the power converters inthe ECS2100 Digital Excitation System. In multiple-bridgesystems any one of the power converters can be turned offand repaired without affecting the operation of the otherbridges. In systems utilizing pullout drawers when a redun-dant drawer is present, any drawer can be removed underfull load by cranking out the drawer.

Bridge Control Module (BCM)The ECS2100 systems are configured with one or moreBridge Control Modules (BCM). A BCM is located in eachconverter bridge assembly. The BCM generates the firingpulses needed to fire the SCRs in the full converter. A state-select port on the BCM is used to select which channel is tobe in control.



Monitoring functions of each BCM include the conduction ofthyristors, the temperature of the bridge, and an optionalmagnitude of bridge current feature.

Power Converter AssemblyEach power converter for this application is packaged in athree-phase, six-thyristor, full-wave bridge configuration thatincludes a BCM module. The power converter appliespositive and negative forcing voltage to the exciter field fordual directional forcing of field voltage. The field current,however, is not reversed. The thyristors conduct currentonce each cycle at a variable angle in the cycle as deter-mined by the amplified error signal from the regulator. Theearlier in the cycle that the thyristors conduct, the greater theamount of energy delivered to the field. Thus, the regulatorcontrols excitation by varying the output of the poweramplifiers by controlling the associated firing circuits.

Some of the power converter bridges are constructed ofdrawout, compact module subassemblies that can beelectrically isolated to facilitate maintenance under load orfixed bridge assemblies. Drawout power converters permiteasy removal of a complete power converter for benchtesting. These modular bridges can be stacked to limit thecubicle floor space required for the ECS2100 DigitalExcitation System.

Power RedundancyThe ECS2100 is configured to optionally add a spareoperating power converter and associated BCM. Withredundancy, maintenance can be performed under full load.This redundancy is important to assure that the failure of oneof these modules or components does not cause a unit trip.

The ECS2100 Digital Excitation System has the capability toadd redundancy in a single channel or in multiple channelconfigurations. This redundancy permits generator opera-tion at rated load with one power converter assemblydeactivated.

Thyristor ProtectionRC snubber networks protect the thyristors against exces-sive rate of change of current and voltage. Nonlinear resistorassemblies protect against excessive transient reversevoltage. For large static exciter systems, ac line filters aretypically used. Protection against loss of pulse in a firingcircuit and loss of conduction in any converter bridgeassembly is provided. Volt-Traps or MOVs (Metal OxideVaristors), used as line surge protection devices, areincluded across the input lines to the converter input.Thyristor overtemperature is monitored by thermal sensors(RTD's) embedded in the heatsinks. The thermal sensorsprovide heatsink temperature indication. Typically, only thehottest heatsink is displayed.

Cooling SystemFor drawout converters, a main fan with a backup fansupplies forced-air cooling. The fan is designed to provideadequate cooling for the entire power cubicle. An automaticfan transfer circuit is included should the main fan fail. The

fans are located in the top front and top back of the powercubicle. The fan assembly is designed to allow removalunder load. A motor protection circuit is included, as well asa loss of airflow alarm. A fan selector switch is providedwhich allows the main fans to be alternated between the twofans.

For fixed bridge assemblies, the power converters may beeither convection cooled or fan cooled depending on thecombination of power converter rating required and con-verter size. If fans are used, they are mounted on each heatsink of the three-phase power converter or on the cubicledoor depending on the field current requirements. Thecurrent rating is reduced without the fans, and the convertermay be operated at reduced load without them. Manyapplication requirements can be met with convection cooingonly.

CONTROL AND MAINTENANCE FEATURES

Operator InterfaceFlexibility in the ECS2100 control room interface capabilitypermits the operator to monitor status, perform controloperations, and make routine adjustments in the voltageregulator. For replacement installations, the customer maychoose to use an existing control room panel. In that case,the system is operated with traditional switches, lights, andmeters connected to programmable I/O terminals. For newinstallations or for sites where the customer chooses toreplace existing controls, the ECS2100 can be connected tothe control room by a single cable. Control then may bedone through the Color Touch Screen Operator ControlModule (See Fig. 6). This module can be mounted locally onthe excitation cubicle or remotely in the control room, or itcan be mounted at both locations. Critical switches such asthe ac supply breaker can be direct connected to a relay viaa terminal block.

Alternately, control may be done through the plant digitalcontrol system via a communication processor in thatsystem.

The excitation control system can also be interfaced to aSCADA remote terminal unit, a process controller, or abackup set of control room switches, lights, and meters.

11

Figure 6 - Color Touch ScreenOperator Control Module


Printed in U.S.A.Printed in U.S.A.Printed in U.S.A.Printed in U.S.A.Printed in U.S.A.

Route 143, Box 269, Highland, Illinois U.S.A. 62249Tel +1 618.654.2341 Fax +1 618.654.2351

e-mail: [email protected]

No. 1300 North Zhongshan Road, Wujiang Economic Development ZoneSuzhou, Jiangsu Province - P.R.China 215200

Tel +86(0)512 6346 1730 Fax +86(0)512 6346 1760e-mail: [email protected]

P.A.E. Les Pins, 67319 Wasselonne Cedex FRANCETel +33 3.88.87.1010 Fax +33 3.88.87.0808

e-mail: [email protected]

Controller Configuration Tool (ccTool)The ccTool is an easy-to-use software tool for configuring,monitoring, and maintaining the ECS2100 Digital ExcitationControl System purchased. It provides operators andmaintenance personnel with password access to theoperational parameters and optional configuration manage-ment of the ECS2100 Digital Excitation System through alaptop or desktop PC.

Level 1: View, the basic access capability, includes theability to monitor generator system values, digital regulatoroperating parameters such as gains, time constants, andlimiting and protective set points, and view job-specificdrawings, instruction books, help menus and help screens.

Level 2 (includes Level 1): Settings allows a user to modifyselectable and adjustable parameter settings.

Level 3 (includes Levels 1 and 2): Configuration Manage-ment includes capabilities for the reconfiguration ofsoftware regulator function blocks and sequence controlconnections.

The ccTool can be accessed locally or from a remotelocation through the RS232 port on the ECM module.

The access capability also includes the ability to view thedata collected by the ECS2100 Transient Event Recorder.The Transient Event Recorder is a software package thatincludes the standard Event and Alarm recorder that isaccessed through Level 1: View of ccTool. Special featuresinclude the optional Single Event Recorder and Analyzer,and the optional Data Logger applications programs, both ofwhich are accessed through optional Level 3: ConfigurationManagement of ccTool. All events are time and date-tagged.

ccTool is compatible with industry standard software such asEmbedded Windows NT and Windows XP.

Transient Event RecorderThe Transient Event Recorder is a software package thatconsists of three applications programs for recording andprocessing transient events.

Event and Alarm RecorderThe Event and Alarm Recorder generates a time and datestamped list of events. The events and alarms included inthe list are pre-selected. The following items are included:

• Pickup of limiters• Operation of limiter• Pickup of protection functions• Operation of protection functions• Internal failure in the controllers

Up to 2000 events may be recorded, then uploaded to apersonal computer file using ccTool. An ACCESS spread-sheet may be used for viewing or printout.

Single Event Recorder and AnalyzerThe Single Event Recorder records up to eight simultaneoussignals. These signals can be selected from any input oroutput signals and selected internal signals. The recordshows both pre-trigger and post-trigger information. Thesystem provides a time that the event trigger occurred. Aselectable remote trigger or an internal one can initiate theevent recording. The Single Event Recorder can accept atime synchronization command from an external sourcesuch as a personal computer or plant digital control system.

Each record contains up to 9600 points per channel. Theresolution is sufficient to allow a cycle-by-cycle analysis foran event. Up to 4 records are stored. The time betweenrecorded points, as well as the number of recorded points, isadjustable. The minimum time between recorded points isone millisecond.

These data points can be viewed using a personal computerthat can be directly connected to the ECM or connected viaa modem to the ECS2100 Digital Voltage Regulator. UsingccTool, data for the event can be uploaded to a text file andviewed directly. The output file from the transient event iscompatible with commercially available software such asMicrosoft EXCELTM. Using such commercially availablesoftware, one can also view and plot the recorded informa-tion without being connected to the excitation system.

Data LoggerThe Data Logger is a log of the value of selected inputs. Theitems to be logged are selectable from 1 to 12 items. Thelast 1000 samples of an item that is contained in a circularbuffer are logged. The following is a list of items that, as aminimum, may be logged:

• Generator output such as watts, vars, power factor• Excitation cubicle output, amps, and volts• Field temperature

The time between value readings is selectable in one-second increments starting at one second. When requested,the last 1000 values logged may be uploaded using ccTool.The log can be stored on disk or printed.


mailto:[email protected]

http://www.basler.com



Documents

ECS2100 ECA2bull