Reason for Load spike when system frequency is disturbed

H

Hfzaal

Gas turbines are on temperature control with droop function active. that mean it will not take more load even if droop demands it. so why at the time of tripping of complex under frequency protection, i always see there is load peak (for example if complex output is 200MW it jumped 230MW)? effects can be seen on all three units. 2 gas turbines and one steam turbine

B

Bob Johnston

Droop will demand more load if the speed drops, that is the whole idea of droop. Search the forums, there has been so much written about this before

H

Hfzaa

BOB ....thank u very much for your reply...but my question is for instantaneous load peak on frequency dip....at such short period of time droop function can only generate demand but actual turbine output can never be increased in mili seconds...

PhilCorso

Hfzaal... the disturbance you describe becomes the "local-generator connected to the non-infinite bus" scenario!

Ignore the action usually mandated, i.e., immediate separation! Instead consider the situation equal to that of dissimilar generators in parallel. Upon a grid-frequency change, the local generator will try to supply the entire load as “altered” by the frequency (and probable subsequent voltage) change!

Regards, Phil Corso