Suppose you have a 3-phase Y source(phases ABC) with a line voltage of 20,5kV.Suppose now that a short-circuit occurs between 2 phases and the ground.The positive sequence impedance(Z1) is 1,3Ohms , the negative sequence impedance(Z2) is 1,25Ohms and the zero sequence impedance(Z0) is 2.1Ohm.

My book says that if the fault is L-L-G the sum of the sequential currents I1+I2+I0 = 0 and that the sequential voltages V1=V2=V0 = 1/3Vph.

I then calculated the sequential currents:I1 = V1/Z1,
I2 = V2/Z2
and I30= V0/Z0.

My book also says that the phase current of the phase which isnt short-circuited (IA=0).

I then tried to calculate the phase currents of IB and IC:
IB = I0+a^2*I1+I2*a
and IC = I0+a*I1+a^2*I2

but I feel I have done something wrong.Any help?

 

Hi,

What is it exactly that you 'feel' you have done wrong?

Do you know how to analyze three phase systems using complex numbers? That gives you a method to check any result you get from another method like the method of symmetrical components. This means you would always have a second method to make sure you got it right.

 

Hi,

What is it exactly that you 'feel' you have done wrong?

Do you know how to analyze three phase systems using complex numbers? That gives you a method to check any result you get from another method like the method of symmetrical components. This means you would always have a second method to make sure you got it right.

Hi.This is my first time doing symmetrical component analysis so I am afraid I have done something wrong.I could be correct but I dont know.

 

Hi.This is my first time doing symmetrical component analysis so I am afraid I have done something wrong.I could be correct but I dont know.

Hi,

Do you know how to use complex numbers (and with that complex number math) ?