Distance Relay Facing Backward

Well you could check the wiring is correct, followed by the relay settings.

It is possible it is something as simple as incorrect wiring or settings.

What has changed since the commissioning records were taken, Boss?

If your work force was so incompetent that they miswired a 33kV sub-station transformer by connecting 33kV to the 132V side then instead of stepping down the voltage to 132V you'd (briefly) step up the voltage to 8,250kV. No testing will be needed to detect this type of a fault, failure will be immediate and catastrophic.

So I don't think that this is what happened but it is the only scenario that comes to my mind that you are proposing. You see your subject in the second sentence is the undefined pronoun "it". This tells me that either you have given us a poor English translation of what you wanted to ask or that you know nothing about high voltage power distribution.

Only knowledgeable and authorized people should work on anything in a sub-station. Ask your on site engineer what to do. If their answer makes no sense to you, bring their answer to us and we will try to explain.

What do you know mr Redfred. You make me sick with all your dumb comments. Did you ever think that maybe someone was observing and wanted to know the answer. It depends on which side the secondary point of the ct's are star pointed and then you have to tell the relay which side is star pointed. If you draw it out on paper it becomes clear. To prove the settings you have to do a dynamic test which involves adjusting the settings on load to make a healthy condition look bad and vice versa. Best regards

isatanimu,

The distance relay will have a few protection elements looking in the forward direction (towards the OHL) and one element looking in the reverse direction (towards station busbars / transformer). The reverse looking element is set with low impedance value so that it cannot see faults in the 33kV side of the transformer and limit its operating zone for faults in 132kV busbars / 132kV windings of the transformer. The element also is time delayed.

In your case, it is possible that the reverse looking element is set to see in to the 33kV system but the time delay is not coordinated with the Transformer O/C protection operation.

If you could review the impedance setting calculation and the basis for time delay settings, the issue should become clear.

Trust the above is helpful.