# Elec Eng AC 3 Phase Symmetrical Components Q - Phase to Fault question

1. Oct 7, 2014

### CasterSkux

Hello again,

I've got another question that involves symmetrical components, this time I've attempted it.

The Question follows:

1. In a 3 phase circuit with resistance earthed and neutral and earth fault in phase “A” which produces a fault current of 800 amps.

Load currents may be taken as zero.

What will be the positive, negative and zero sequence currents in this system?

I have Ia = 800 for Phase A, Ib = 0 and Ic = 0 and I assume this is a Phase-to-earth fault

According to this source https://www.selinc.com/WorkArea/DownloadAsset.aspx?id=100688, when Phase B and Phase C is zero (as suggested by "Load currents may be taken as zero"): the zero,
positive and negative sequence are all 1/3Ia. It also says that when an phase to earth fault happens in Phase A: Phase B and Phase C can be assumed to have no current anyway.

Therefore Ia = 800A and I0, I1, I2 = 267A. Is my answer and thought process right?

Cheers:)

2. Oct 8, 2014

### zoki85

Yes, it's correct