Transmission Line: X0 = (2~3.5) times X1. 

Transformer:  X0 = X1 = X2

Synchronous Generator: X0 < X1

for lines zero seq. is more than Positive seq. 

Not necessary. For transformers and synchronous generators, zero sequence reactance x0 should be smaller than positive and negative sequence reactance x1 and x2.

For transmission lines, zero sequence reactance x0 should be smaller than positive and negative sequence reactance x1 and x2 ,which is about 2~3.5 times of X1 sounds right to me and I agree with Krishnarayalu Movva. Hope helps - Ning

For lines the Zpos = Zneg = R + j w (L-M), but Zo = R +j w (L+2M) + 3 Zground.

So the Xo is bigger because of the +2M (mutual induction) and the 3 times the Ground Reactance. The Ro is only bigger because of the 3 times Ground Resistance.

Everything fine. In addition, you should consider the effect of the coupling of the transformers. Consider a generator connected to the network throgh a D/Yg step-up transformer. Seen from the HV side the positive  sequence resistance is Rg*K^2+Rt; the zero sequence resistance is Zt only, where Rg is the generator resistance; K is the transformer ratio and Rt is the short circuit resistance of the transformer seen from the HV side. The very same consideration apply to the reactance. In practical cases the ratio of Zo/Zd can be lower than 1/3. E.g. (on the same basis) Zg=0.25, Zt= 0.12, Zo/Zd=12/37.

As an extreme case a Yg/D transformer at no load seen from the Y terminals presents at the positive sequence the magnetizing impedance and at the zero sequence the short circuit impedance.

We normally for Transformer use Xo= 0 .9 * X1 as rule of thumb where I work, and it seems to be working fine. I am presently applying that now busy Real time digital simulations in Pullman.

how can i clculate z0 z1 z2

Hi Mousa Elroby,

I can help you with the expression in the attached file. Hope this helps.

Kind regards,

Ning