Capacitor Inrush Current

[electricnewbie]

Hello all,
I’m trying to find the inrush current a new 12 (24MVAR future) 115kv Capacitor bank. I found the formula:

I(max)=1330*?(KVAR/LS) for 60hz,
Where, LS is the system inductance in microhenries.

Now, I know that:
Xl=2?fL=377*L
Or...
L=Xl/(2*pi*f)

So my question is, should I just use the positive sequence X (in ohms given from CAPE) to get my LS? Or should I include the neg and zero sequence X values?


X (ohms)
+seq: 21.505
-seq: 21.525
0seq: 26.356

Thank you in advance.

 

[magoo2]

Yes, the positive sequence impedance is what you want.

 

[bacon4life]

12 MVAR seems like a pretty small bank at that voltage. Does your utility use very many that size?

 

[electricnewbie]

That is the typical size of bank at that voltage. Most new bank locations have two 12 MVAR banks, each with their own breaker.

The utility also has several smaller sub-transmission cap banks to support the 115kV voltage.

 

[davidbeach]

Two 12MVAr banks at 115kV seems about right to me.

 

[bacon4life]

Oh, now I see your system has pretty low fault values, so even that size bank is a pretty big change in voltage.