6.22
SEL-311C Relay Instruction Manual Date Code 20060320
Close and Reclose Logic
Reclosing Relay
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 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.
In Table 6.6, note that the open interval 1 time (setting 79OI1) is a short time,
while the following open interval 2 time (setting 79OI2) is significantly
longer. For a high magnitude fault (greater than the phase instantaneous
overcurrent element 50P2 threshold), open interval 1 time is skipped, and
open interval timing proceeds on the following open interval 2 time.
Once the shot is incremented to shot = 1, Relay Word bit SH0 = logical 0 and
then setting 79SKP = logical 0, regardless of Relay Word bit 50P2.
Additional Settings Example 2
If the SEL-311C is used on a line serving an independent power producer
(cogenerator), the utility should not reclose into a line still energized by an
islanded generator. To monitor line voltage and block reclosing, connect a
line-side single-phase potential transformer to channel VS on the SEL-311C as
shown in Figure 6.7.
Table 6.6 Open Interval Time Settings Example
Shot
Corresponding
Relay Word Bit
Corresponding
Open Interval
Open Interval
Time Setting
0 SH0 79OI1 30 cycles
1 SH1 79OI2 600 cycles
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