Answer Posted / henry vakharia
Current transformers are classified in two categories viz.
protection and measuring classes.
In protection relay, the earth fault is detected from the
earthed terminal or say the common terminal shorted
together and then grounded, which makes the relay detect
the earthfault other than its core function of protecting
equipments from high voltage surges.
In measuring relay, the C.T. is grounded to give protection
from the primary high voltages surges.
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