7-24 Maintenance and Testing Date Code 20000421
SEL-251, -2, -3 Instruction Manual
3. You can test the reclosing relay sequence coordination feature using the same
procedure in Reclosing Relay Open Interval Timer Test steps 6 through 8
without monitoring open interval times. Since no overcurrent trip condition is
given (TR = 0), the relay does not trip when you apply current. It remains in the
reset state with the circuit breaker closed.
However, SEQ = 50L, so the shot counter is incremented every time the circuit
breaker is closed (IN5 = 52A is asserted), you apply and turn off current above
the 50L level (4.00 A), and no TRIP output contact asserts. Every time the shot
counter is incremented by SEQ pickup and dropout, the reset interval timer is
reinitialized and starts timing. The reclosing relay remains in the reset state (A1
= 79RS remains asserted).
In application, sequence coordination advances the shot counter, keeping the
SEL-251 Relay in step with line reclosers (see Multiple Shot Reclosing Relay in
Section 2: Specifications). If the reset interval timer expires before current
rises above and falls below the 50L level again, the shot counter resets to shot =
0.
The number of reclosing shots (automatic reclosures) depends on the number of
set open interval times. In this example there are three open intervals, so there
are three shots.
79SH asserts according to the M79SH setting. M79SH can be set for any com-
bination of shots 0, 1, 2, 3, and 4. As previously mentioned, the number of shots
depends on the number of set open interval times; this example uses three set
open interval times. M79SH is set for shot = 1 and shot = 3:
M79SH = 01010
Thus, 79SH will assert only when shot = 1 or shot = 3.
The shot = 4 position in the M79SH setting (right most position) is not appli-
cable in this example because there are only three shots.
The A4 output contact is used to monitor shot counter increments (A4 = 79SH).
4. Follow the procedure in Reclosing Relay Open Interval Timer Test steps 6
through 8 (remember that the relay will not trip). When the applied current is
removed, the shot counter increments from shot = 0 to shot = 1 and the reset
interval timer is reinitialized. Because of the M79SH setting (M79SH = 01010),
the A4 output contact also asserts (A4 = 79SH). The shot counter remains at
shot = 1 and the A4 output contact remains asserted until:
The circuit breaker remains closed throughout reset interval time
(79RST = 1800 cycles), the shot counter reverts back to shot = 0, and the
A4 output contact deasserts (A4 = 79SH). The front panel RS (reset)
LED remains illuminated and the A1 output contact remains asserted
(A1 = 79RS).
or
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