Capacitor at generator output 3

[tem1234]

Hi,

I've remark that on a lot of small hydro generator (4-5 MW), there's a little 3 phases capacitor just at the output of the generator, in the junction box, where the cables from the switchgear are connected. There is also surge arrestor connected in parralel at this location.

My question is, what's the purpose of this capacitor? The generator is synchronous, so no need to correct the power factor.

Thanks

 

[VTer]

it's for surge protection of generator - see

http://www.abb.com/product/db0003db002618/c12573e7003302adc1257053004b6e49.aspx

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

 

[rcw retired EE]

Surge arrestors clip the voltage at some level but do nothing to prevent fast rise time voltage surges less than its protection level. The capacitors limit the rise time of incoming voltage surges. A steep fronted surge slamming into the winding impedance can damage the winding insulation.

Capacitors and surge arrestors work together. The capacitor handles the dV/dt; the surge arrestor clamps the voltage peaks and protects the capacitor as well as the winding.

 

[tem1234]

Thank you guy, very informative.