capacitor bank connection in MV grids 2

[prismpower]

hello everybody,

i am working on specifications for 33kV and 22kV grid. i want to specify the power factor correction capacitor banks. what is better for the internal connection of the capacitors? Delta or wye? Ive read that as per standard IEEE Std 1036-1992; Delta connected capacitors are suitable for voltages up to 2.4kV. can i still specify Delta connected capacitors to eliminate harmonics and increase the gird stability?

cheers,

 

[Power0020]

They do work fine, but, economics may not help with delta connected capacitors to withstand the line-to-line voltages.

Not aware with unbalance protection in delta with MV, but i doubt that the third harmonic may circulate within the delta (as it does in LV).

All of MV capacitors I have seen are ungrounded wye or double wye.

 

[jghrist]

Are the capacitors in the substation or on the MV line? If pole-mounted, this may be of use:

http://castlepowersolutions.biz/Com... Capacitor Units/Kilo_Var_Briefs/Issue 20.pdf

 

[cuky2000]

For 33 kV system, cap banks tends to point installations towards wye connected configuration.
Delta cap bank connection at 33 kV could be technically feasible. However, will be economical and space penalty since optimum connection for a shunt cap bank depends on the best utilization of the rated voltage and protective scheme used. As mentioned above, virtually all HV and sub-transmission substation banks are connected wye for a good reason.
If the concern is to mitigate harmonics and grid stability, there are other options available such as install harmonic filters.
Although the IEEE & IEC standard practice for cap bank connection could have some differences, both practices do not recommend delta connection for 33 kV (see the info below).

 

[prismpower]

thanks everyone. great answers indeed!