I am trying to understand the method to detect ground fault if you have an ungrounded system. In a few literatures I read that you will use relay 59G to sense gorunded overvoltage. Because the ground fault current in this setup is very small, they said that you will require a sensitive device like directional overcurrent relay like device 67 in order to trip the circuit. First, is this a common strategy for these type of system? Is you have high resistance grounded circuit, would the situation be different? When using HRG system, the benefit is the grounded voltage cna be stablized, as compared to unground sytsem, so, then, is that an issue with using device 67 which uses the grounded voltage (in ungrounded system) to determine a trip setting, knowing the setting range will be sensitive. My apology if the question is confusing, as I am confused.
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