Transmission ground distance relaying with distribution underbuild

[stevenal]

How do you handle the mutual coupling?

1. Ignore it.
2. Carefully model the distribution circuit(s) and mutual(s) in your fault program.
3. Model just the distribution neutral in your fault program.
4. Measure the line impedances including the mutual coupling with test equipment.
5. Use actual fault data to estimate the parameters.
6. Avoid using ground distance. (In favor of?)
7. Something else. (What?)

Thanks for sharing.

 

[stevenal]

I had the path wrong on G-H, it does share a path with F-G for part of it's length.

As far as G-H coupling with F-H, would a parallel path 2000 ft away for 2.4 miles have an effect?

 

[bacon4life]

Prefault current of 17 amps might be a branch/tree sitting on the line for a short duration before the fault evolves to low impedance.

Can you post the waveform recording? When the fault magnitude varies throughout the fault it is unclear to me which instant the relay uses to calculate the location.

Mutual coupling is inversely related to separation distance, so lines 2000 feet apart would have very tiny impact.

 

[stevenal]

Thanks.
Not much fault variability once it got beyond the "pre-fault" stage. I tried some calculating in Sychrowave Event, zoomed in on the pre-fault.