Unformatted text preview: ary winding of current
transformer (C.T.) is insufficient to operate the trip coil of the breaker but the contacts can be opened
(and hence the circuit can be opened) by manual or remote control. When a fault occurs, the resulting
overcurrent in the C.T. primary winding increases the secondary e.m.f. This energises the trip coil of
the breaker and moving contacts are pulled down, thus opening the contacts and hence the circuit.
The arc produced during the opening operation is quenched by the oil. It is interesting to note that
relay performs the function of detecting a fault whereas the circuit breaker does the actual circuit
interruption. 4. Relays. A relay is a device which detects the fault and supplies information to the breaker
for circuit interruption. Fig. 16.1 (ii) shows a typical relay circuit. It can be divided into three parts v iz.
(i) The primary winding of a *current transformer (C.T.) which is connected in series with the
circuit to be protected. The primary winding often consists of the main conductor itself.
(ii) The second ci...
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- Spring '12
- Electrical Engineering, Short circuit, Fuse, Circuit breaker