ANSI 86 Master Trip Lock-Out Relay

This lock-out relay is an electromechanical protection device designated ANSI Device 86, the master trip relay used across power system protection schemes. Actuated by an upstream protective relay such as a differential, ground fault, or overcurrent relay, it trips its output contacts and mechanically latches in the tripped position, blocking further breaker closure until a technician performs a manual reset. This behavior prevents automatic re-energization of a faulted circuit and gives investigation crews a clear indication of which protection element operated.

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. Overload capacity supports 95 A at 120 VAC across 50 operations, with contact resistance specified at 10 milliohms maximum. Multiple contact stacks can be configured for simultaneous trip, alarm, indication, and interlock functions, allowing a single relay to drive breaker trip coils, annunciator inputs, SCADA status points, and interlock circuits from one lockout event.

Rotor contacts use phosphor bronze dual-wiper construction, and stationary contacts are silver-plated copper, in a panel-mount design suited to interchangeable substation and switchgear layouts. Typical applications include substation transformer differential protection, generator differential protection, bus differential schemes, motor protection, transformer overcurrent lockout, and any power system installation where master trip logic and manual reset are specified.