Point on Wave Switching for Capacitor Banks
Point on Wave Switching for Capacitor Banks
(OP)
Can anyone tell me the benefits of point on wave (POW) swicthing for 90MVAR cap banks shunt connected in utility applications at 132kV. The untis are typically installed with high series reactance (ie. 6.5%), so would POW be justified?






RE: Point on Wave Switching for Capacitor Banks
Theoretically, the POW can be programmed to minimize inrush current on closing and avoid trapped charges on the capacitors after breaker opening. We have only used them on 230 kV and above systems to minimize transformer and line charging curents. (The alternative was to use a closing resistor but it was not available on GIS equipment.)
We do not have experience using POW with cap banks.
RE: Point on Wave Switching for Capacitor Banks
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Point on Wave Switching for Capacitor Banks
Unfortunately, we never did any field measurements to verify that the study correctly predicted the system response.
Another thing to consider is how often they will be switched. Ours are switched in in the fall and taken back out of service in the spring. If they were switched multiple times a day, there would be a much greater opportunity for the transients to cause harm.
RE: Point on Wave Switching for Capacitor Banks
POW switching would be for energising transients on a cap bank/filter bank.
The initial voltage collapse is given by dV=Ls/(Ls+Lf); where Ls = source inductance and Lf = filter inductance.
For a large bank such as b4l's above and assuming a fault level of say 2000MVA at 50Hz we would have :
dV = 21mH/(21mH + 5mH) = 0,80p.u. or 80%, which is serious.
For a smaller bank, say 25MVAr tuned at 4,8p.u. Lf would be about 76mH which would only give a collapse of about 22% which is acceptable (this would further be reduced by system damping).