Transmission Line negative sequence impedance

[wowski]

We have twin EHV transmission lines approx 80km in length which are closely in parallel for their entire lengths, and are not transposed. Using Transmission Line Impedance calculators with the physical phase positions indicates that the negative and positive sequence impedances are not equal and are significant for the mutual parameters. Loadflow programs generally rely on the +ve and -ve seq impedances being the same. My question is has anybody else had this problem with trying to model line behaviour for loadflows in situations like this? SCADA data of MVAR flows on these lines do not match the predicted loadflow results due to the above. Comments and advice appreciated.

 

[mersin33]

for a line, postive and negative sequence data should be same. similarly for any passive element like transformers.

could you pls advise what program you used to calculate the parameters?

 

[Bung]

Most line impedance calculators for load flow and fault level studies assume balanced, transposed lines. If this is not the case, then sequence components may not give an accurate model. You may have to do the calculations using something like ATP, EMTP or PSCAD/EMTDC to model each phase individually.


Bung
Life is non-linear...