A circuit breaker closes and opens an electric circuit under both load and fault
conditions. There are two types of circuit breakers, dead tank and live tank. Dead tank
circuit breaker means that the external source and load connections are made through
conventional bushings, circuit breaker tank and all accessories are maintained at
ground potential. Live tank circuit breaker means that the interrupting mechanism is
mounted on an insulating porcelain column and maintained at line potential.
Substation circuit breakers are also classified as three-pole-single-throw and
independent pole operation. Three-pole-single-throw circuit breakers utilize one
mechanical device to trip all three poles together and independent pole operation circuit
breakers utilize one mechanical device per pole to trip individual pole. Figure 3-10, 5-2,
and 5-3 shows the power circuit breaker one line, dead tank, and live tank breaker.
Figure 3-10: Circuit Breaker
(Shown with Bushing-Type CTs and Reclosing Relay)
