Schweitzer Engineering Laboratories SEL-351A - Table 6.5 Example Open Interval Time Settings; Figure 6.7 Reclose Blocking for Islanded Generator

6.24
SEL-351A Relay Instruction Manual Date Code 20080213
Close and Reclose Logic
Reclosing Relay
In Table 6.5, 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-351A is used on a feeder with a line-side 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-351A
as shown in Figure 6.7.
Figure 6.7 Reclose Blocking for Islanded Generator
If the line is energized, channel VS overvoltage element 59S1 can be set to
assert. Make the following setting:
79STL = 59S1 + ...
If line voltage is present, Relay Word bit 59S1 asserts, stalling open interval
timing (reclose block). If line voltage is not present, Relay Word bit 59S1
deasserts, allowing open interval timing to proceed (unless some other set
condition stalls open interval timing).
Additional Settings Example 3
Refer to Figure 6.4 and the accompanying setting example, showing an
application for setting 79STL.
Table 6.5 Example Open Interval Time Settings
Shot
Corresponding
Relay Word Bit
Corresponding
Open Interval
Open Interval
Time Setting
0 SH0 79OI1 30 cycles
1 SH1 79OI2 600 cycles
SEL-351A
Bus 1
52
IA, IB, IC
VA, VB, VC
VS
3-Phase
1-Phase
Generator
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