Generator over Fluxing Relay (24G
[LEFT]
[B][I][U][F**T="]Generator over Fluxing Relay (24G)[/F**T][/U][/I][/B] [B] -The relay measures the ratio of voltage to frequency (V/Hz) as this ratio is proporti**al to the flux-density level of the electromagnetic machine.[/B] [B]-Over Fluxing (Over Excitati**) may be occur when a generator is ** an isolated operati** with the AVR in service and the generator speed decreasing from the synchr**ous speed.[/B] [B]-Over Fluxing may also be occurring when the utility system frequency decreases to a low value by any reas**.[/B] [URL="http://3.bp.blogspot.com/_CZnqYQLLQtc/TR936cGYLUI/AAAAAAAAAHk/fWe1cQjG6DI/s1600/Over_flux.JPG"][IMG]http://3.bp.blogspot.com/_CZnqYQLLQtc/TR936cGYLUI/AAAAAAAAAHk/fWe1cQjG6DI/s400/Over_flux.JPG[/IMG][/URL] [B]There are two sets of the V/Hz relays are provided for Generator Protecti**:-[/B] [U][F**T=Impact] A) Relay 24G (#2) for alarm[/F**T][/U] [B]A definite time element #2 of the relay will be used to provide an alarm.[/B] [U][F**T=Impact]B) Relay 24G (#1 & INV) for trip[/F**T][/U] [B]Operati** of the relay 24G will trip the switchyard breaker.[/B] [B]An inverse time element of the relay will be used to provide a trip c**tact and a definite time element #1 is also used to further shape the protecti** curves.[/B] [B][U][F**T="]Data for setting calculati**s[/F**T][/U][/B] [B][I]Short-time V/Hz withstand level at full load -----120%[/I][/B] [B][I]C**tinuous V/Hz withstand level at full load-----105%[/I][/B] [B][I]AVR V/Hz limiter setting -----------------------------105%[/I][/B] [U][F**T=Impact] Setting of generator V/Hz alarm relay 24G (#2)[/F**T][/U] [B][I][U]1)V/Hz alarm setting[/U][/I][/B] [B]Setting < c**tinuous V/Hz withstand level at full load = 105 %[/B] [B][I][U]2)V/Hz alarm delay[/U][/I][/B] [B]Setting = 30 cycles (0.6 Sec.)[/B] [U][F**T=Impact] Setting of generator V/Hz alarm relay 24G (INV)[/F**T][/U] [B][I][U]1) V/Hz trip setting for inverse time element[/U][/I][/B] [B]Setting = 107 %[/B] [B][I][U]2) V/Hz Reset rate for inverse time element[/U][/I][/B] [B]Reset rate = Practical recommendati** is minimum setpoint of the relay [/B] [B]Setting = 1 Sec.[/B] [B] [/B] [B]NOTE!! “If the generator is synchr**ized immediately after tripping by V/Hz relay operati**, the generator will be damaged under V/Hz c**diti** before limitati** value. “ [/B] [U][F**T=Impact]Setting of generator V/Hz alarm relay 24G (#1)[/F**T][/U] [B][I][U]1)V/Hz alarm setting[/U][/I][/B] [B]Setting < short V/Hz withstand level at full load = 120 %[/B] [B][I][U] [/U][/I][/B] [B][I][U]2)V/Hz alarm delay[/U][/I][/B] [B]Setting = 50 cycles (1 Sec.)[/B][/LEFT] |
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