Answer Posted / madhu
the neutral grounding transformer is star connected on the
primary and has an open delta on it's secondary.Open Delta
has two terminals.A resistor is conected across these two
terminals. whenever a fault occurs, an emf will be induced
in the open delta and there will be a voltage drop in the
resistor connected. this voltage drop will be sensed by the
potential transformer connected across this resistor. at
the secondary of the potential transformer we have the
neutral displacement relay which will give a trip signal or
an alarm whenever its settings exceed a particular value.
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