Patent ID: 7570471

Claim:
A zone-selective-interlocking (ZSI) system for an electrical power distribution system having at least one upstream breaker and at least one downstream breaker comprising: a zone-selective-interlocking circuit connected to the at least one upstream breaker and the at least one downstream breaker; and a monitoring portion of the at least one upstream breaker to verify the connection of the zone-selective-interlocking circuit to the at least one upstream breaker and the at least one downstream breaker, wherein the monitoring portion of the at least one upstream breaker measures a signal level of a ZSI signal input of the at least one upstream breaker, and determines that an open circuit condition exists between the at least one upstream breaker and the at least one downstream breaker in the zone-selective-interlocking circuit based a measured first signal level of the ZSI signal input, determines that a proper connection condition exists between the at least one upstream breaker and the at least one downstream breaker in the zone-selective-interlocking circuit based on a measured second signal level of the ZSI signal input, and determines that both of a restraint signal is sent from the at least one downstream breaker to the at least one upstream breaker and that said proper connection condition exists based on a measured third signal level of the ZSI signal input.