Parameter estimation of transmission line

[leoliu]

Does someone have working experiences to calculate transmission line parameters (R, X, and/or B) based on real-time telemetries at line terminals(P, Q, KV)? This is to verify line parameters calculated by system planning. It is important for relay settings.

 

[davidbeach]

You need I and V, magnitude and phase angle, at precisely the same time. Synchrophasors are what you need.

 

[leoliu]

Thx. My question is if someone really did the test and/or calculation. "Synchrophasor" can be obtained by PMU (phasor measurement unit) or EMS (energy management system in control centers) estimations.

 

[davidbeach]

It's trivial if you have the synchrophasor data. I'm not aware of an EMS the has PMU capabilities. The calculation has to be done using data from both ends gathered at precisely the same time, but then it is just a simple power system analysis homework problem where you are given the voltages at both ends, the current through the impedance and need to calculate the impedance. Piece of cake. The only difficulty is in obtaining the data.

 

[jghrist]

Calculation of positive-sequence impedance by classical means is pretty accurate, so calculating with synchrophasors is not very important. It's the zero-sequence impedance that involves a lot of estimation for classical calculation. With balanced loads, you can't do it with synchrophasors either. You need to have a ground fault or a lot of imbalance.

 

[davidbeach]

Yeah, good point. Zero-sequence is very difficult to get nailed down. But for the purposes of a system model used for state estimation, all that is needed is the positive-sequence network.