Fault Current Calculation
Fault Current Calculation
(OP)
Ok, So I have
X/R Ratio
Peak fault Current
RMS fault Current
of a 33kV nominal network
How do I calculate the specific X and R values from this for a netwrok infeed, ETR 120's just confusing me...
And how do I calculate the equivalent network infeed
I think it would be
S = (V*V) / (SQRT((X*X)+(R*R)))
X/R Ratio
Peak fault Current
RMS fault Current
of a 33kV nominal network
How do I calculate the specific X and R values from this for a netwrok infeed, ETR 120's just confusing me...
And how do I calculate the equivalent network infeed
I think it would be
S = (V*V) / (SQRT((X*X)+(R*R)))






RE: Fault Current Calculation
From what I have understood,
you have a RMS fault current, take its reciprocal multiply by the base MVA and you got it.
cheers !
RE: Fault Current Calculation
RE: Fault Current Calculation
RE: Fault Current Calculation
In most cases, the sofware asks for or assumes a default value of the X/R ratio which for a 33kV system could be 8, 10, 12 or 15 at the max. Also it depends on the purpose of you analysis also. If this is for sizing ratings of 33kV or lower equipment, above assumption would suffice.
RE: Fault Current Calculation
RE: Fault Current Calculation
Cheers for that, and I'll check out red book too
Would this be acurate enough for getting X and R from the ratio?
X = Z sin ([tan-1](X/R))
R = Z cos ([tan-1](X/R))
And then sizing a slack bus according to the RMS fault contribuiton
RE: Fault Current Calculation
RE: Fault Current Calculation
I've seen this used before
S being the rating of the Slack Bus
S=(V*V)/Z
Now if the slack is given the stated RMS fault contribution from the network we have S and V so Z is easy to get... however, how accurate do you think this would be?
RE: Fault Current Calculation
Plus I do not know what a Slack bus is. May be you can explain little more or someone else can chime in..
RE: Fault Current Calculation
RE: Fault Current Calculation
Then what Cooda76 said is correct method to find Z.
Then use the formulas you indicated for R and X in your second last post. I think you have it there..