Islanded Generating Stations

[mbrooke]

How do Islanded generating stations respond during line short circuits? How does the critical clearing time change? Something like this as an example >

https://imgur.com/WklBJCs

 

[ron]

The clearing time is related to the available short circuit current from the source and the protective device settings. Just like any source. The islanded plant just has less available fault current, like a standby optional or emergency generator at a building.

 

[mbrooke]

The clearing time is related to the available short circuit current from the source and the protective device settings. Just like any source. The islanded plant just has less available fault current, like a standby optional or emergency generator at a building.

So something like a few cycles I take it in terms of CCT. Do close in faults vs farther out faults make a difference? My understanding is that generators speed up for faults that are mostly reactive.

 

[zbang]

Islanded but not small. With proper governors, I'm not sure how any of the generators could speed up; isn't reactive power controlled by excitation?

 

[mbrooke]

Islanded but not small. With proper governors, I'm not sure how any of the generators could speed up; isn't reactive power controlled by excitation?

It is by the excitation, but during a fault R (MWs) dip and reactive lagging power (VAR) goes up.