Buzzing Capacitor Bank
Buzzing Capacitor Bank
(OP)
We have a pole mounted, 200 KVAR per phase, grounded wye capacitor bank on a 12.47 kV rural distribution feeder. During a recent line patrol, it was reported that an audible hum or buzz could be heard around this bank that was 'similar to, but slightly louder than that of a medium sized three phase distribution transformer' (500 - 1000 KVA).
When removed from service, the hum remained until the last unit was taken off line. The crew performing the line patrol changed out each of the capacitors with new units, and put the bank back in service, with the noise immediately returning.
A later check of the removed units with a capacitance meter indicated no problems.
Our primary line is 336 ACSR, with a bank of 437 Amp voltage regulators that is approximately 3 miles upline of the capacitors. Loading is residential and agricultural, with no loads that I would consider unusual. This is the only capacitor bank that I know of on the circuit.
Noone here has ever before encountered a noisy capacitor bank, and an online search has turned up nothing. I thought of harmonics and resonance, but I would expect blown fuses and damaged capacitors to be the symptoms of either of these situations.
Any thoughts on this situation would be appreciated.
When removed from service, the hum remained until the last unit was taken off line. The crew performing the line patrol changed out each of the capacitors with new units, and put the bank back in service, with the noise immediately returning.
A later check of the removed units with a capacitance meter indicated no problems.
Our primary line is 336 ACSR, with a bank of 437 Amp voltage regulators that is approximately 3 miles upline of the capacitors. Loading is residential and agricultural, with no loads that I would consider unusual. This is the only capacitor bank that I know of on the circuit.
Noone here has ever before encountered a noisy capacitor bank, and an online search has turned up nothing. I thought of harmonics and resonance, but I would expect blown fuses and damaged capacitors to be the symptoms of either of these situations.
Any thoughts on this situation would be appreciated.






RE: Buzzing Capacitor Bank
RE: Buzzing Capacitor Bank
RE: Buzzing Capacitor Bank
RE: Buzzing Capacitor Bank
I had some amp readings taken at the location yesterday. It was a very mild afternoon, so loading was light. Without the capacitors, we found phase currents of 7,20,26 Amps, and current on the grounded-neutral of 11 Amps. With capacitors in service, we found upline readings of 29,31,38 and 13(neutral); and downline readings of 8,18,25 and 10 (neutral). About 10 minutes or so probably elapsed between the downline and upline readings.
We will probably just keep an eye out for blown fuses or bulging tanks, and leave the capacitors in service. The buzzing is not coinciding with an any apparent operational problems.
-Robert
RE: Buzzing Capacitor Bank
Anyway, you might ask your infra-red guy to take a close look at it next time he's in the area to see what comes up.
Also... do you have anything you use to check for corona or leaks? For instance Ultraprobe UE2000 from UESystems ultrasonic device can help you localize exactly where the noise is comming from.
RE: Buzzing Capacitor Bank
RE: Buzzing Capacitor Bank
RE: Buzzing Capacitor Bank