22
SEL Application Guide 2020-04
Date Code 20200326
to determine how long it takes for the remote relay distance element to pick up and
transmit data to the local relay via a M
IRRORED
B
ITS
channel.
Equation 5
The final calculated value of the coordination time delay timer (21SD) is 1.40 cycles.
Recommendations for 67SD Timer
The recommended setting for the 67SD timer is the sum of the following three times:
➤
Control input recognition time (including the debounce timer)
➤
Remote Level 3 nondirectional low-set overcurrent element maximum operating time
➤
Maximum communications channel time
67SD Calculation for SEL-421-5
For the control input recognition time and maximum communication channel time calculations for
the SEL-421-5, see
21SD Calculation for the SEL-421-5
Remote Level 3 Nondirectional Low-Set Overcurrent Element Maximum Operating Time
The remote relay in this example is the SEL-311C-0. The maximum Level 3 operating time of the
SEL-311C-0 is 1.50 cycles.
Use
to determine how long it takes for the remote relay overcurrent element to pick up
and transmit data to the local relay via a M
IRRORED
B
ITS
channel.
Equation 6
The final calculated value of coordination time delay timer (67SD) is 2.01 cycles.
67SD Calculation for SEL-311C-0
For the control input recognition time and maximum communication channel time calculations for
the SEL-311C-0, see
21SD Calculation for the SEL-311C-0
where:
0.90 is the distance element operating time
0.50 is the control input recognition time
0.01 is the data communications delay
Total delay
0.90 0.50 0.01
+
+
1.40 cycles
=
=
where:
1.50 is the overcurrent element operating time
0.50 is the control input recognition time
0.01 is the data communications delay
Total delay
1.50 0.50 0.01
2.01 cycles
=
+
+
=
