21
Date Code 20200326
SEL Application Guide 2020-04
Maximum Communications Channel Time
The maximum communications channel time is the same as the time calculated for the SEL-421-5
because the distance between the relays and the type of fiber used for communications is the same.
Remote Zone 3 Distance Protection Maximum Operating Time
The remote relay in this example is the SEL-421-5. Refer to the SEL-421-5 instruction manual and
[7] for more information about the Zone 3 distance protection maximum operating times.
and
show the operating curves for high-speed distance elements.
Consider the worst-case operation and assume SIR = 1. The maximum operating time of a distance
element is about 0.90 cycles.
Figure 19
Operating Time Curve of the SEL-421-5 for a Phase-to-Phase Fault
Figure 20
Operating Time Curve of the SEL-421-5 for a Phase-to-Ground Fault
Fault Location in Percent of Set Reach
0
20
40
60
80
100
Ti
me
in Cycles
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
Fault Location in Percent of Set Reach
0
20
40
60
80
100
Ti
me
in Cycles
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
