Power System Capacitive Charging Current 2

[kmh1]

Does anyone have a good reference on estimating or calculating power system capacitive charging current in order to apply system ground fault protection in medium voltage applications?

 

[AMBMI]

An empiric equation which could be used to calculate the current flowing through the cable capacitance is
I = 0.2 * U * length
where
"I" is the capacitive current in A
"length" is the cable length in kilometers
"U" is the cable rated voltage in kV
It could be interesting to know how long such current lasts.
Usually to avoid spurious trips a 0.2 s delay is used for the ground elements

 

[Eleceng01]

One could also use an EMTP-type program to model the cable and observe the charging current. An example program would be ATP (Alternative Transients Program) - it is free though a little learning curve is required. I used it in a college class and this is one of the things that we used it for.

 

[LMBT]

You can take maybe a look at Post Glover website and their High Resistance Grounding Application Guide:

http://www.postglover.com/Literature/HR003-05_High_Resistance_Ground_Gde.pdf