Protection Engineering Basics and Schemes Protection Engineering | Page 33

I r + I y + I b = I e = 0

Then every current have 3 components Positive Sequence Current = I 1 Negative Sequence Current = I 2 Zero Sequence Current = I 0

So , I r = I r1 + I r2 + I r0 I y = a 2 I y1 + aI y2 + I y0 I b = aI b1 + a 2 I b2 + I bo a = 0.5 − j0.866 a 2 = −0.5 − j0.866 1 + a + a 2 = 0

Now if system is balance ; = I r + I y + I b

= I r0 + I r1 + I r2 + I y0 + a 2 I y1 + aI y2 + I b0 + aI b1 + a 2 I b2 − − − − − − − − ( Eq 1 )

Pl remembers ;

I r0 = I y0 = I b0 And for the calculation purpose ,

I y1 = I 1 and I y2 = I 2 pg . 33