A lockout relay is a type of relay that is used to isolate or lock out a circuit or equipment from the power source in case of a fault or abnormal condition.

It is also known as a master trip relay or an 86-relay, according to the ANSI code¹.A lockout relay is usually placed before or after the emergency stop switch, so that the power can be shut off at one central location.

This relay is powered by the same electrical source as the control power and is operated by a key lock switch². A lockout relay can also receive signals from multiple protection relays and send commands to multiple breakers, interlocks, alarms, data displays, SCADA extensions, and other devices¹.

A lockout relay is essential for the safety and protection of high voltage equipment such as transformers, generators, switchgear, etc. It prevents further damage by not allowing remote reset of the system after a fault.

Manual recognition of the fault intensity and manual reset is required².I hope this information is helpful for you.