Date Code 20001006 Close and Reclose Logic 6-25
SEL-351 Instruction Manual
After successful reclose initiation, open interval timing does not start until allowed by the stall open
interval timing setting 79STL. If 79STL = logical 1, open interval timing is stalled. If 79STL =
logical 0, open interval timing can proceed.
If an open interval time has not yet started timing (79STL = logical 1 still), the 79SKP setting is
still processed. In such conditions (open interval timing has not yet started timing), if
79SKP = logical 1, the relay increments the shot counter to the next shot and then loads the open
interval time corresponding to the new shot (see Table 6.3). If the new shot turns out to be the
“last shot,” no open interval timing takes place, and the relay goes to the Lockout State if the
circuit breaker is open (see Lockout State earlier in this subsection).
If the relay is in the middle of timing on an open interval and 79STL changes state to 79STL =
logical 1, open interval timing stops where it is. If 79STL changes state back to 79STL =
logical 0, open interval timing resumes where it left off. Use the OPTMN Relay Word bit to
monitor open interval timing (see Monitoring Open Interval and Reset Timing earlier in this
subsection).
Factory Settings Example
The skip shot function is not enabled in the factory settings:
79SKP = 0 (numeral 0)
The stall open interval timing factory setting is:
79STL = TRIP
After successful reclose initiation, open interval timing does not start as long as the trip condition is
present (Relay Word bit TRIP = logical 1). As discussed previously, if an open interval time has
not yet started timing (79STL = logical 1 still), the 79SKP setting is still processed. Once the trip
condition goes away (Relay Word bit TRIP = logical 0), open interval timing can proceed.
Additional Settings Example 1
With skip shot factory setting:
79SKP = 50P2 * SH0
if shot = 0 (Relay Word bit SH0 = logical 1) and phase current is above the phase instantaneous
overcurrent element 50P2 threshold (Relay Word bit 50P2 = logical 1), at the instant of successful
reclose initiation, the shot counter is incremented from shot = 0 to shot = 1. Then, open interval 1
time (setting 79OI1) is skipped, and the relay times on the open interval 2 time (setting 79OI2)
instead.
Courtesy of NationalSwitchgear.com
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