Input functions are explained below:
Direct Trip (DT)
Assertion of the DT input causes the TRIP output to close immediately and unconditionally if
so enabled (see LOGIC MTU command). It also cancels any reclose initiation or reclose
sequence if so enabled in the MRC mask (see the LOGIC MRC command) and triggers an
event report. The TRIP output remains closed as long as the DT input is asserted and drops
out about 0.5 cycle after the DT input deasserts or approximately TDUR time after the TRIP
output first closed, whichever is later. Applications include reclose cancel, test trip and
Direct Underreaching Transfer Trip (DUTT) schemes. The OPEN command has the same
effect as the DT input.
Direct Close (DC)
The Direct Close input causes the CLOSE output to close, as long as no trip condition is
detected and the 52A input is not asserted. The CLOSE output stays closed until the 52A
input asserts or until the reclosing relay reset interval expires, whichever occurs first. No
event report is triggered. The CLOSE command has the same effect as the DC input.
Permissive Trip (PT)
The PT input is normally used in permissive transfer tripping schemes. When it asserts, an
event is triggered and additional tripping conditions are allowed as selected in the logic setting
procedure (see the LOGIC MPT command).
Block Trip (BT)
The BT input is normally used in blocking and fuse saving schemes. When it is not asserted,
selected tripping conditions are allowed (see the LOGIC MTB command). This input also
triggers an event report.
Circuit Breaker Monitor (52A)
The 52A input indicates the state of the breaker. The 52A is used by the tripping and closing
functions and in the reclosing relay.
External Trigger for Event Report (ET)
An event report is triggered whenever the external trigger input is asserted. Asserting this
input does not influence the protective functions in any way.
2-8
Specifications
SEL-267D/167D Instruction Manual
Date Code 920326
Summary of Contents for SEL-167D
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