Answer / prashant singh

the main factor to deside defferential relay is used in
transformer or motor or generator is-
1. the current ratio of primary & secondary winding.
2. the current ratio in motor o/p terminal and star
terminal of machine.
3. same as generator.
in normal machine like transformer we connect a ct
to the primary & secomdary winding. and after connecting ct
we take both side ct terminal and joint in differential
connection, in this connection the resultant current is
zero. if any foult is generate resultant is not zero. and
this is due to fault.

Answer / karthik

The differential relay is used in places where a vector
difference of current exist.Some examples are
transformers(current difference between primary and
secondary),generator(current difference between stator two
sides of a stator winding.

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% voltage variation in distribution a)1% b)5% c)10% d)15%

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