Medium Voltage Capacitors

[bnewport]

In a medium voltage substation with a grounded capacitor bank, how much current would normally flow to ground? Other than testing the de-energized caps with a Fluke meter, how can I determine what is causing the current and if it is acceptable?

Bryan

 

[bob]

Re: Medium Voltage Capacitors

Capacitor load is no different that any other 3 phase load when speaking of load flow. If the caps are ok the 3 phase load should cancel and there should be no neutral current. What problems are you having? ARe you taking a clip-on reading at the neutral connection to the caps?
Don't forget harmonic currents. They flow to capacitor banks.

[ May 13, 2005, 12:37 PM: Message edited by: bob ]

 

[bnewport]

Re: Medium Voltage Capacitors

Bob-

I am not having any problems...yet... I have to go next week to check substation grounding. The details are minimal so far, but I guess they have about 7 amps on the ground, even with the caps offline. I need to track down this source of ground current. I am not a high voltage guru, so I am not sure where to begin. Any ideas?

Bryan

 

[physis]

Re: Medium Voltage Capacitors

Let me start with:

I have absolutely no experience with the kind of applications you're talking about. But.

This is how to calculate capacitive reactance:

1/2PifC or

1/((2)(Pi)(frequency)(caqpacitance))

The reciprical of 2 x 3.141 x 60 Hz. x (capacitance in Farads)

This is the impedance of a capacitor.

An Example.

A 6.7 MF capacitor shunted across a 60 Hz. sourse.

1/6.283 x 60 x .000,0067

1/.002526

396 ohms impedance.

At 600 volts:

600/396 = 1.515 amps.