Apparatus and method for servicing a distribution bus

摘要

Protection is provided for servicing a distribution bus (5) by grounding the line side (11) of a circuit breaker (7) through which the distribution bus (5) is fed and then closing the circuit breaker (7). The trip unit (21) of the circuit breaker (7) includes logic (29), in addition to the normal protection logic, which opens the circuit breaker main contacts (17) without delay if current is detected upon closing of the grounded circuit breaker (7). However, if the grounded circuit breaker (7) has been closed for a selected period of time and then current is detected, the distribution bus (5) is kept at zero potential by not operating the breaker (7). A breaker auxiliary switch (25) with a mechanical delay provides the indication of the selected time interval after closing the circuit breaker (7).