Neutral Grounding Transformer 1

[kingi]

This is a solidly grounded star on the primary and open corner delta, with resistor in the delta, on the secondary grounding transformer on a 12.6 kV delta system. The transformer permits 15A 3Io current in the star ground. There are a few feeders with negligible capacitance but two of the feeders have 3-4 A capacitive current.

How do I calculate the feeder ground relay settings that will not result in sympathetic tripping (tripping of a feeder for a ground fault on another feeder)? How do I combine the capacitive charging current with the transformer 3Io current? Can I neglect the capacitive current in the setting calculations? Is there any source of information that will sufficiently discuss this problem?

 

[lume7006]

Hello,

You may look at several websites from relays manufacturers, they do typically have some papers in which they discuss topics like yours.
I recommend you to visit GE and/or SEL.

Another good reference could be some books, you may take a look at: Protecive Relaying from Mr Blackburn, he typically details step by step.