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Generator reactances...help required

Generator reactances...help required

Generator reactances...help required

(OP)
i am working on a offshore marine project where i have ended up with generator rating of 8000kW, at 11kV, 60Hz. With 12% subtransient reactance i am getting s.C level of 29kA. i am not sure of the sub transient reactance values to be considered for such hv rating generators??
i always had the impression that 10-15% sub transient reactance is normal.....going above 18-19% becomes costly affair.....

any inputs on how to choose the optimum value? highest/lowest values based on generator ratings? any selection ways?

help required.

RE: Generator reactances...help required

I may be reading you comment wrong but the %reactance should be on the name plate. 8000kw/11x1.73 = 420amps/0.12 = 3500 amps.

RE: Generator reactances...help required

Reactances for a 5MW 13.8kV machine are    
Xd    1.33PU
X'd    0.124PU
X"d    0.089PU

Reactances for a 18MW 13.8kV machine are
Xd     1.587PU
X'd    0.179PU
X"d    0.126PU

Something to compare it to.

RE: Generator reactances...help required

(OP)
i am aware its on nameplate. but since i am in basic design stage i am more keen on knowing the generally available reactance values for 8MW generator rated 11kV, 60Hz, diesel engine driven.

RE: Generator reactances...help required

Speed?

RE: Generator reactances...help required

(OP)
720rpm

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