7-26
Maintenance and Testing
Date Code 20000421
SEL-251, -2, -3 Instruction Manual
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.
.
CFT
= 120
close failure time (cycles)
.
.
.
IN4
= DC
direct close
IN5
= 52A
circuit breaker auxiliary
The choice of inputs IN4 and IN5 is for demonstration purposes only.
Connect the CLOSE output contact to an external timer so the timer starts upon
CLOSE output contact assertion. The close failure timer in the relay also starts
at CLOSE output contact assertion.
The CLOSE output contact remains asserted until the close failure timer expires
or the circuit breaker auxiliary contact input to the relay (IN5 = 52A) is
energized (circuit breaker successfully closed). In this test, no circuit breaker
simulator is connected to either the IN5 input (IN5 = 52A) or the CLOSE output
contact. IN5 remains de-energized and the relay considers that the circuit
breaker is open.
Connect the A4 output contact to the same external timer to stop the timer when
the A4 output contact asserts. A4 contact assertion indicates that the relay failed
to close the circuit breaker within the time allotted by the CFT setting;
CFT = 120 cycles; A4 =
CF
, close failure condition.
Assert the relay CLOSE output contact using the CLOSE Command or by ener-
gizing the IN4 input (IN4 = DC) function. The external and close failure timers
start. Input IN5 must remain de-energized (IN5 = 52A).
When the close failure timer expires, close failure condition
CF
asserts for 60
cycles and the A4 output contact asserts (A4 =
CF
). A4 output contact assertion
stops the external timer. The CLOSE output contact deasserts when the
CF
bit
asserts and the A4 output contact deasserts 60 cycles after asserting. Compare
the external timer reading to the close failure time setting (in this example
CFT = 120 cycles).
Trip Failure Timer Test
Purpose:
Verify the operating time of the trip failure timer.
Method:
1. Using the SET n command (n is the active setting group), program an element
(e.g.,
50L
, phase overcurrent pickup) for tripping via the programmable tripping
variable TR:
close TRIP output contacts = TR + ...