Earthing Transformer or grounding transformer is the neutral grounding transformer - star connected on the primary and has an open delta on secondary. Open Delta has two terminals. A resistor is connected across these two terminals.
Whenever a fault occurs, voltage 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 earthing transformer connected across this resistor. At the secondary of the earthing transformer we have the neutral displacement relay which will give a trip signal or an alarm whenever its settings exceed a particular value.
Earthing transformer can also be called a large Potential transformer (Open delta PT).
Whenever a fault occurs, voltage 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 earthing transformer connected across this resistor. At the secondary of the earthing transformer we have the neutral displacement relay which will give a trip signal or an alarm whenever its settings exceed a particular value.
Earthing transformer can also be called a large Potential transformer (Open delta PT).
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