ABB REC670 2.1 IEC Product Manual

Contents

ABB REC670 2.1 IEC Product Manual Manual pdf 24 page image

7. Frequency protectionUnderfrequency protection SAPTUF M13349-3 v12Underfrequency occurs as a result of a lack of generation inthe network.Underfrequency protection SAPTUF measures frequency withhigh accuracy, and is used for load shedding systems,remedial action schemes, gas turbine startup and so on.Separate definite time delays are provided for operate andrestore.SAPTUF is provided with undervoltage blocking.The operation is based on positive sequence voltagemeasurement and requires two phase-phase or three phase-neutral voltages to be connected. For information about howto connect analog inputs, refer to Application manual/IEDapplication/Analog inputs/Setting guidelinesOverfrequency protection SAPTOF M14953-3 v11Overfrequency protection function SAPTOF is applicable in allsituations, where reliable detection of high fundamental powersystem frequency is needed.Overfrequency occurs because of sudden load drops orshunt faults in the power network. Close to the generatingplant, generator governor problems can also cause overfrequency.SAPTOF measures frequency with high accuracy, and is usedmainly for generation shedding and remedial action schemes.It is also used as a frequency stage initiating load restoring. Adefinite time delay is provided for operate.SAPTOF is provided with an undervoltage blocking.The operation is based on positive sequence voltagemeasurement and requires two phase-phase or three phase-neutral voltages to be connected. For information about howto connect analog inputs, refer to Application manual/IEDapplication/Analog inputs/Setting guidelinesRate-of-change frequency protection SAPFRC M14965-3 v12The rate-of-change frequency protection function SAPFRCgives an early indication of a main disturbance in the system.SAPFRC measures frequency with high accuracy, and can beused for generation shedding, load shedding and remedialaction schemes. SAPFRC can discriminate between apositive or negative change of frequency. A definite time delayis provided for operate.SAPFRC is provided with an undervoltage blocking. Theoperation is based on positive sequence voltagemeasurement and requires two phase-phase or three phase-neutral voltages to be connected. For information about howto connect analog inputs, refer to Application manual/IEDapplication/Analog inputs/Setting guidelines.Frequency time accumulation protection FTAQFVRGUID-020CE8CF-9BEA-455D-ACBD-13023B93B4D1 v4Frequency time accumulation protection FTAQFVR is basedon measured system frequency and time counters. FTAQFVRfor generator protection provides the START output for aparticular settable frequency limit, when the system frequencyfalls in that settable frequency band limit and positivesequence voltage within settable voltage band limit. TheSTART signal triggers the individual event timer, which is thecontinuous time spent within the given frequency band, andthe accumulation timer, which is the cumulative time spentwithin the given frequency band. Once the timers reach theirlimit, an alarm or trip signal is activated to protect the turbineagainst the abnormal frequency operation. This function isblocked during generator start-up or shut down conditions bymonitoring the circuit breaker position and current thresholdvalue. The function is also blocked when the system positivesequence voltage magnitude deviates from the given voltageband limit which can be enabled byEnaVoltCheck setting.It is possible to create functionality with more than onefrequency band limit by using multiple instances of thefunction. This can be achieved by a proper configurationbased on the turbine manufacturer specification.8. Multipurpose protectionGeneral current and voltage protection CVGAPC M13083-11 v9The General current and voltage protection (CVGAPC) can beutilized as a negative sequence current protection detectingunsymmetrical conditions such as open phase orunsymmetrical faults.CVGAPC can also be used to improve phase selection forhigh resistive earth faults, outside the distance protectionreach, for the transmission line. Three functions are used,which measures the neutral current and each of the threephase voltages. This will give an independence from loadcurrents and this phase selection will be used in conjunctionwith the detection of the earth fault from the directional earthfault protection function.Voltage-restrained time overcurrent protection VRPVOCGUID-935E1CE8-601F-40E2-8D22-2FF68420FADF v6Voltage-restrained time overcurrent protection (VRPVOC)function can be used as generator backup protection againstshort-circuits.The overcurrent protection feature has a settable current levelthat can be used either with definite time or inverse timecharacteristic. Additionally, it can be voltage controlled/restrained.One undervoltage step with definite time characteristic is alsoavailable within the function in order to provide functionalityfor overcurrent protection with undervoltage seal-in.1MRK 511 361-BEN BBay control REC670 2.1 IECProduct version: 2.124 ABB