Schweitzer Engineering SEL-351P - Other Setting Considerations for SEL-351 P(1) and SEL-351 P(2) Recloser Controls; Settings Example 2

6-10 Close and Reclose Logic Date Code 990215
SEL-351P Manual Técnico
Other Setting Considerations for SEL-351P(1) and SEL-351P(2) Recloser Controls
Refer to Skip Shot and Stall Open Interval Timing Settings (79SKP and 79STL, respectively)
in the following Reclosing Relay subsection.
SEL
OGIC Control Equation setting 79STL stalls open interval timing if it asserts to logical 1. If
setting 79STL is deasserted to logical 0, open interval timing can continue.
The SEL-351P(1) has no intentional open interval timing stall condition (circuit breaker 52/1
closes first after a transmission line fault):
79STL = 0 (numeral 0)
The SEL-351P(2) starts open interval timing after circuit breaker 52/1 at the remote end has
reenergized the line. The SEL-351P(2) has to see Bus 2 hot, transmission line hot, and in
synchronism across open circuit breaker 52/2 for open interval timing to begin. Thus,
SEL-351P(2) open interval timing is stalled when the transmission line voltage and Bus 2 voltage
are not
in synchronism across open circuit breaker 52/2:
79STL = !25A1 [=NOT(25A1)]
Note: A transient synchronism check condition across open circuit breaker 52/2 could possibly
occur if circuit breaker 52/1 recloses into a fault on one phase of the transmission line.
The other two unfaulted phases would be briefly energized until circuit breaker 52/1 is
tripped again. If channel VS of the SEL-351P(2) Relay is connected to one of these
briefly energized phases, synchronism check element 25A1 could momentarily assert to
logical 1.
So that this possible momentary assertion of synchronism check element 25A1 does not
cause any inadvertent reclose of circuit breaker 52/2, make sure the open interval timers
in the SEL-351P(2) are set with some appreciable time greater than the momentary
energization time of the faulted transmission line. Or, run the synchronism check element
25A1 through a programmable timer before using it in the preceding 79CLS and 79STL
settings for the SEL-351P(2) (see Figure 7.23 and Figure 7.24). Note the built-in 3-cycle
qualification of the synchronism check voltages shown in Figure 3.24.
Settings Example 2
Refer to subsection Synchronism Check Elements in Section 3: Overcurrent, Voltage,
Synchronism Check, and Frequency Elements. Also refer to Figures 6.3 and 6.4.
If the synchronizing voltages across open circuit breaker 52/2 are “slipping” with respect to one
another, the Reclose Supervision Limit Timer setting 79CLSD should be set greater than zero so
there is time for the slipping voltages to come into synchronism. For example:
79CLSD = 60.00 cycles
79CLS = 25A1
The status of synchronism check element 25A1 is checked continuously during the 60-cycle
window. If the slipping voltages come into synchronism while timer 79CLSD is timing,
synchronism check element 25A1 asserts to logical 1 and reclosing proceeds.