Protection Engineering Basics and Schemes Protection Engineering | Page 68

connected holding contacts. After which PR contact de
energized, this arrangement is to prevent chattering in
circuit, and from holding circuit current signal will flow,
this current from holding circuit first put Flag indication
on and then flow towards the breaker auxiliary contacts
(52a) and make it closed to energize the trip coil of
breaker, trip coil then pull up the plunger or trip the
breaker.
2.3.2 Shunt Reinforcement:
In this trip circuit, when protection relay (PR) contacts
(Make Contact) closes and parallel auxiliary contacts
(make contact) with flag indication simultaneously
closes, the flag indication show on indication, on that ON
indication the other (Upper) parallel make contact
energizes after which PR make contact and parallel make
contact de-energize to prevent PR contact from
chattering issue, and current flows toward breaker
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