20
SEL Application Guide 2020-04
Date Code 20200326
Consider the worst-case operation time and assume SIR = 1. The maximum operating time of a
distance element is about 1.90 cycles.
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 3
The final calculated value of the coordination time delay timer (21SD) is 2.40 cycles.
21SD Calculation for the SEL-311C-0
Control Input Recognition Time
shows the M
IRRORED
B
ITS
data delay times for different baud rates [4].
The SEL-311C-0 relay with a baud rate of 38400 has a typical data delay of 8.3 ms because its pro-
cessing interval is 1/4-cycles. With this information, use
to calculate the data delay in
cycles.
Equation 4
Figure 18
Operating Time Curve of the SEL-311C-0 for a Phase-to-Ground Fault
SIR = 0.1
SIR = 1.0
SIR = 10.0
SIR = 30.0
0
10
20
90
30
40
50
60
70
80
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2.25
Fault Location in Percent of Set Reach
Oper
ating Time in C
ycles
2
where:
1.90 is the distance element operating time
0.50 is the control input recognition time
0.01 is the data communications delay
Total delay
1.90 0.50 0.01
+
+
2.40 cycles
=
=
Data delay
0.0083 s
=
Data delay
60.0000 0.0083
0.5000 cycles
=
•
=
