10.4.6 Monitored dataPID-6515-MONITOREDDATA v4Table 181:FTAQFVR (81A) Monitored dataName Type Values (Range) Unit DescriptionFREQ REAL - Hz Measured frequency valueACCTIME REAL - s Accumulated time forfrequency band limits10.4.7 Operation principle GUID-DB8A3411-2FA6-47B1-BC75-9892BD224DC0 v4Frequency time accumulation protection function FTAQFVR (81A) is used to protectthe turbine against an abnormal frequency operation. During the startup and shutdownof the turbine-generator set, FTAQFVR (81A) is blocked to avoid unnecessaryaccumulation of time or tripping of generator. FTAQFVR (81A) is also blocked whenthe system positive-sequence voltage magnitude deviates from the given voltage bandlimit, which can be enabled with the EnaVoltCheck setting. The overall logic ofFTAQFVR (81A) is explained in Figure112.The frequency of the measured input voltage is monitored continuously and comparedto the set frequency band limits FreqHighLimit and FreqLowLimit. When the measuredsystem frequency is above the FreqLowLimit setting and below the FreqHighLimitsetting, the FREQOK and PICKUP signals are activated. The BFI_3P signal iscontrolled by the measured current and voltage input magnitude and the status of thecircuit breaker position.FTAQFVR (81A) function will block BFI_3P signal activation and Accumulation oftime under two following conditions even if the system frequency falls within set bandlimits.• When the generator is not synchronized as indicated by the CBOPEN signal input:Generator currents are considered to detect whether the generator is supplying itsunit auxiliary supply transformers or not. FTAQFVR (81A) function will beblocked when the measured current magnitude drops below the settingPickupCurrentLevel and CBOPEN input is high. FTAQFVR (81A) remainsblocked until the generator returns to the operation condition. It can be verified byusing the CBCLOSE signal. Generator's start and stop detection logics for theBFI_3P output can be ignored by disabling the CBCheck setting.• When the positive-sequence voltage of the measured input voltage is outside theband limit.The BFI_3P output will be blocked if the EnaVoltCheck setting is enabled and thesystem positive sequence voltage is not within the voltage band limits.1MRK 511 408-UUS A Section 10Frequency protectionPhasor measurement unit RES670 2.2 ANSI 321Technical manual
