Answer / arpita

Under normal operating condition m.m.f or ampere- turn
both primary and secondary oppose each other. When
secondary of C.T is open circuited then there is no
demagnetiging ampere-turn to oppose the primary ampere-turn
and therefore, the primary ampere-turns now become active
in producing a very high flux density in the core which
result in very high inductance e.m.f. in the secondary
winding.
This high induced e.m.f. is likely to cause
a) Overheating of core
b) Breakdown of insulation
c) An electric shock to the attending personnel.
For these reason secondary of C.T in power system not act
as an open circuit.

Answer / gajanan

there are 2 possibilities
1.if we keep secondary of ct open, then only primary mmf
will be present in core which saturates the core
2.in fault condition due to high frequencu current core
saturates means permeability of core decreases very much as
good as wood

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