How to read on SEL311 the distance a fault has occurred?

[SA07]

Hi
The SEL 311 relay between our substation and the utility substation has tripped.
LED on are C, G, 87
Can you plz explain how to read the distance where the fault has occurred?
We need to do an inspection to locate the fault. Thks

 

[davidbeach]

Download the event report. Even just look at the event summary. How accurate the fault location is depends on a number of factors, the most important of which is accurate circuit impedance values entered into the relay program.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[stevenal]

For 87, two relays are involved. It is likely that one relay detected the fault first and sent a transfer trip to the other one. If this is the case, only the first relay will have an accurate fault distance. Suggest getting event records from both.

 

[SA07]

The utility relay detected the fault first as their breaker opened first. Their relay identified the fault at 1 km. This corresponded exactly to the pole of the damaged isolators.
While our relay identified the fault at 6.34 km. The length of the line is 4.8 km.

 

[Palletjack]

These relays calculate distance based on circuit impedance as stated above.
They work and calculate distance best when all conditions are met. One being a true fault, a wire touching another wire or a ground reference.
If there happens to be an arcing fault where no wires are touching, the distances will be off.
I’ve seen them off by 5 miles for a switch that opened under load and stopped about 1/4 travel distance.
The point is, don’t assume the distance is dead on, but don’t dismiss it completely because it’s off a time or two.

 

[davidbeach]

And that’s all based on the settings. If the utility had the line impedance entered correctly but your end didn’t, that would explain it.

I’ll see your silver lining and raise you two black clouds. - Protection Operations