The ‘a’ and ‘b’ contacts from each of these relays are interlocked with other relays or switches such that they either permit or not permit the breaker operation. Circuit Breaker Trip Schemeįor the trip circuit, you must wire the tripping relays’ ‘a’ contact in parallel. Therefore when any one relay or switch contact closes, thus completing the circuit, the breaker trips. The only exception to the parallel wiring of contacts is the low-gas auxiliary relay contact (63X in the figure).
Modern power circuit breakers employ Sulfur Hexa-Flouride (SF6) gas to extinguish an arc. Reduced interrupting capability, a flash-over can occur inside the tank. To prevent flash-overs due to low gas, breakers are fitted with ANSI ’63’ relay. Tripping of breaker is cut out by this relay’s contact.
