
System Protection 245
of the time-delay characteristic shown in Figure10.10. The trip settings of various
circuit breakers in the system are coordinated such that the circuit breaker closest
to the fault is tripped rst by a relay circuit, keeping the rest of the system operating
normally. In a chain of circuit breakers, the generator breaker should have the longest
trip time setting for a given fault current.
10.4.1 tyPes of CirCUit breaker
Molded case dual-element circuit breaker: This type is generally used for small
LV circuits. It is made of two tripping elements and contacts enclosed in a common
molded plastic case (Figure1 ...