-ve and +ve sequence measurements

[salem]

What is the practical way to measure the –ve and +ve sequence impedances of a 138 kV ,52 km long over head transmission line installed on wooden towers , what is the technical specifications of the equipment needed for this test ?

 

[cuky2000]

The positive and negative sequence impedance, Z+ & Z- for a transmission line should be equals since lines are passive electrical components.

For short transmission line (length <80 kM ~ 50 mi) the Z+ = Z- is equivalent to the voltage measured at the receiving-end (load side) when excited at the sending-end side with a balanced 3-phase voltage source with current of 1 Amp circulating at the receieving-end short-circuited lines.

<sub>OBSERVATION:

i- For short transmission line, the two-port network parameter B = Z = R + j.X

ii-For short circuit at the receiving end (Vr =0).

iii-From the generalized equation

Vs = A.V[blue]r[/blue]+ B.I[blue]r[/blue]= Z.Ir

Therefore, for I[blue]r[/blue]=1Amp, |Z |= Vs[blue]sc[/blue] with an angle= (I<V)</sub>