Network Resistance as a Function of Frequency (Freq. Sweep)

[RodneyDixon]

Hi all,

I have been viewing a demo model wind-farm in one of the main power system analysis softwares. Viewing the frequency sweep results I can see 'Z' which has a resonance point as expected at the PCC at a certain frequency (Utility+Wind-farm connected).

I am also able to display the results in the form of R and X at the PCC. When plotting R it has a similar shape to that of Z. I would of expected R to be be relatively linear with very little slope/fall (also allowing for the skin effect). As this is a demo model it might not be a realistic example but I have seen similar results in IEEE papers.

I have attached a snapshot, as can be seen resonance Z = R as angle of X is 0 degrees.

So, why does the network resistance 'R' measured at the PCC exhibit this characteristic as the frequency increases?

Perhaps I should be looking at how/what the software is exactly calculating.

Any insight would be much appreciated.

Thanks

RD