Answer / g.govarthinam

Dear friends
1.Diff relay compares two currents entering and leaving the
protected equipment or zone in respect of current
maagnitude and phase angle, and if there is any unbalance
or spill current found, that current will flow through the
operating coil of the relay and give trip pulse to the
Circuit breaker to isolate the supply to the transformer.
2.Please note that,Diff relay will operate only for
internal fault of the protected equipment(for
example,winding fault in transformer) and it should not
trip for over load of transformer and any external fault.

please feel free to ask further doubts in this topic.
regards
gova

Answer / m raviteja

differential relay is the difference of current from
primary and secondary of the transformer.Normally setting
is at 0.6% if more than that the transformer will tripped
on that relay fault.
the primary current and secondary currents are connected to
individual ct's and that terminals are connected to relay.
differential relay is of two types voltage based and
current based.Normally current based is used in industries.

testing procedure:both primary and secondary currents are
induced to relay and make the required setting if current
difference is more than that the relay acts.

differential relay will not operate when overload the
transformer unless the difference in primary and secondary
currents

Answer / sathish

which operates on the basis diffence in currents in
windings.

Answer / engr rb

differential rely operatets on differencs in either voltage
or current, these are two diff relays,. definately if the
transf over loaded then voltage will drop and current will
increase so it will cause imbalace in the current and
voltage cosequently rely will be operated.

Answer / sheik hussain

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