ANSI 86 Lock-Out Relay with Push-to-Test

This push-to-test lock-out relay is an electromechanical protection device designated ANSI Device 86, the master trip relay used in power system protection schemes. When operated by a protective relay such as a differential, ground fault, or overcurrent relay, it trips its output contacts and mechanically latches in the tripped position, blocking breaker re-closure until a technician performs a manual reset. This lockout behavior prevents automatic re-energization of a faulted circuit, supporting equipment protection during and after major system faults.

The push-to-test feature adds a maintenance capability that standard master trip relays lack: verifying the trip mechanism is functional while the protected circuit stays in service. A recessed front-panel test button actuates the relay through its full trip cycle without opening the trip output contacts, so the mechanism can be checked during scheduled outages or between operating shifts, reducing the risk that a stuck or degraded relay goes undetected until a real fault occurs.

Continuous contact rating is 30 amperes at 600 volts, with UL interrupt ratings of 25 A at 120 VAC, 15 A at 240 VAC, 6 A at 600 VAC, 3 A at 125 VDC, and 1 A at 250 VDC. Typical applications include substation transformer protection, generator differential protection, bus protection schemes, motor protection, and any power system installation where master trip logic with in-service testing is required.