08-01-2013, 03:58 PM
CIRCUIT BREAKER
[attachment=46723]
Circuit Breaker:
A Circuit Breaker is an equipment that breaks the circuit either manually or automatically under all conditions full load, no load or short circuit condition; by making use of its fixed & moving contacts. This contact can be open manually or by remote control whenever required.
Working principle
Two contacts called electrode remains closed under normal operating condition.When fault occurs on any part of the system, trip coil of the C.B. get energized and contacts are separated.
Arc Phenomena
An arc is struck when the contacts are separated .The current is thus able to continue. Thus the main duty of C.B is to distinguish the arc within the shortest possible time. The arc provides low resistance path to the current and the current in the circuit remains uninterrupted. During arcing period, the current flowing between the contacts depends on the arc resistance. The greater the resistance, the smaller the current that flows between the contacts.
Low resistance or zero current method
All modern high power A.C. circuit breaker employ this method for arc extinction because there is natural zero current present in A.C. system. In a case of a 50 Hz supply there are 100 zeros per second.
This method is explain by two theories:-
Recovery Rate Theory (Slepain’s Theory)
Energy Balance Theory
POTENTIAL TRANSFORMER
It is essentially a step down transformer to step down the voltage to know the ratio 66kv/110 volt
That’s mean primary is 66kv we get by pt 110 volt
[attachment=46723]
Circuit Breaker:
A Circuit Breaker is an equipment that breaks the circuit either manually or automatically under all conditions full load, no load or short circuit condition; by making use of its fixed & moving contacts. This contact can be open manually or by remote control whenever required.
Working principle
Two contacts called electrode remains closed under normal operating condition.When fault occurs on any part of the system, trip coil of the C.B. get energized and contacts are separated.
Arc Phenomena
An arc is struck when the contacts are separated .The current is thus able to continue. Thus the main duty of C.B is to distinguish the arc within the shortest possible time. The arc provides low resistance path to the current and the current in the circuit remains uninterrupted. During arcing period, the current flowing between the contacts depends on the arc resistance. The greater the resistance, the smaller the current that flows between the contacts.
Low resistance or zero current method
All modern high power A.C. circuit breaker employ this method for arc extinction because there is natural zero current present in A.C. system. In a case of a 50 Hz supply there are 100 zeros per second.
This method is explain by two theories:-
Recovery Rate Theory (Slepain’s Theory)
Energy Balance Theory
POTENTIAL TRANSFORMER
It is essentially a step down transformer to step down the voltage to know the ratio 66kv/110 volt
That’s mean primary is 66kv we get by pt 110 volt