Question { 9106 }

what is diffential relay? testing proceure?and
transformer reach Over load thet time differencilal relay
operate or not ?

Answer

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

Question { Indeco, 12760 }

how bucchos relay works in a transformer

Answer

It is a gas actuated relay.It has two floats.
one is top float(bucholz alarm) which is operated when
oil level in transformer decreases and for a minor fault
which is developing.The gas is collected at the top of
bucholz relay, thus displacing the oil in the top and thus
causes the float to fall down and make the NO contact.
The other is bottom float(bucholz trip) which is
operated for a severe fault which causes oil inrush towards
the bottom of bucholz relay and thus causes the float to
make the NO contact thus isolating the supply to the
transformer.Sometimes buchols relay will operate for a
feeder through fault which causes jerk in the transformer
causing oil inrush.
cheers
gova

Question { 41895 }

what is the diff between earth leakage relay and earth
fault relay?

Answer

Hi radhika

Where u find the Earth leakage relay and Earth fault
relay?pl specify the application.

Regards
Gova

Question { 10048 }

Form fator is the ratio of?

Answer

Hi,I am Ganesan Govardhan
Significance of form factor:
When an AC voltage is rectified by a full wave
rectifier,the DC value equals the Average value.
Having given the RMS AC input,we can find the DC output
from the relation

Edc = Erms/Form factor

Question { ABB, 39898 }

why we r used APFC Panel in industrial area.when P.F. low
then wat will be the effect in our system?

Answer

when power factor is unity,then industries receive active
power or useful power only i.e KW=KVA
If it is lagging PF,the industries receive both useful power
(KW) and reactive power(useless power)(KVAr).To meet this
reactive power, distribution transformer capacity also to
be increased.Then only we can avoid low voltage,losses
etc.
So we have to provide APFC panel to bring the pf to unity