An 86 relay, named after ANSI device number 86, is a multi-contact lockout relay driven by trips such as transformer differential, Buchholz or busbar protection. It opens every associated breaker and blocks closing until an operator resets it by hand, which forces a person to look at the plant before it is energised again. The handle stays in the tripped position as a visible indication.
Transformer 2 went out on diff and the 86 is latched, nobody resets it until the oil sample comes back.
'Who reset the 86?' is the question nobody wants to hear after a failed re-energisation.
Also heard as
- 86
- lockout relay
- LOR
Related terms
Differential protection
Scheme that compares current entering and leaving a protected zone and trips when the two disagree.
Trip
To open a circuit breaker automatically through its protection, or to order a breaker open by command.
Flag
Indicator on a protection relay showing which element or phase operated; also the verb for it showing.
Buchholz relay
Gas and oil-surge relay in the pipe between a transformer tank and its conservator that detects internal faults.