Protection of capacitor bank.

[sanjay12345]

Dear all,

I have capacitor bank connected after distribution transformer for the compensation of reactive powers. The capacitor bank is composed of multiple capacitor unit and is connected Y ground. what type of protection needed for this capacitor banks ?

I have designed with following two protection.

1. Overcurrent (Protection against short circuit)
2. Zero sequence overcurrent (Protection against if any single capacitor unit is out of service)


Is there any more protection needed ? Someone suggest me for

Overvoltage protection as well. But this is connected just after distribution transformer so I think over voltage protection is not required for this capacitor bank.

Cap bank connected to long transmission line may require overvoltage protection.

I 'll appreciate all whocan clarify me on this.

 

[msquared48]

Fused disconnects?

Mike McCann
MMC Engineering

 

[amurray]

A couple of other things to consider, though not stricly protection.

Disconnect & circuit breakers rated for capacitive switching

Means to safely discharge capacitors once opened & to prevent quick closing after opening of caps to limit overvoltage issues.

Andy

 

[slavag]

Hi
Its double star connection or single star?
Actually, undervoltage protection, as you saied, overvolage protection, issue here is Q=(about)U^2.

loss of phase,3-ph unbalance,overload, undercurrent protection.

as usually depend on the configuration and size od bank.

 

[DTR2011]

Both SEL and GE have pretty good application papers on their websites about this.

 

[dfdt]

Depending if the capacitor banks are tuned or detuned you may consider Harmonic overload protection to prevent overload of your cap bank due to system harmonics.