P.3.344
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
Protection Application Examples
2.00-3.00 0.0 0.0
3.00-4.00 0.0 0.0
4.00-5.00 0.0 0.0
5.00+ 0.0 0.0
Round-trip delays are in the range of 5 ms for Channel 1 and 1 ms for
Channel 2. Set the Max Round trip Delay for these channels to 8 ms and 4 ms,
respectively. Channel asymmetry is low, and you can attribute a step change in
channel delay to channel switching. Set the maximum step change delay to a
low value (3 ms) to detect this event. The 87L characteristic settings can
accommodate asymmetry of at least 1 ms, or 21.6. Set the maximum
allowable asymmetry to 4 ms for Channel 1 and to 1 ms for Channel 2.
We would have the following at Relay S:
87CH1MT := 8 Max. Round Trip Delay for Ch 1 (OFF, 1.0–50 ms)
87CH1MD := 3 Max. Step Change in Ch 1 Delay (OFF, 3.0–50 ms)
87CH1MA := 4 Max. Allowable Asym. for Ch 1 (OFF, 0.2–10 ms)
We would have the following at Relay R:
87CH1MT := 8 Max. Round Trip Delay for Ch 1 (OFF, 1.0–50 ms)
87CH1MD := 3 Max. Step Change in Ch 1 Delay (OFF, 3.0–50 ms)
87CH1MA := 4 Max. Allowable Asym. for Ch 1 (OFF, 0.2–10 ms)
87CH2MT := 4 Max. Round Trip Delay for Ch 2 (OFF, 1.0–50 ms)
87CH2MD := 3 Max. Step Change in Ch 2 Delay (OFF, 3.0–50 ms)
87CH2MA := 1 Max. Allowable Asym. for Ch 2 (OFF, 0.2–10 ms)
We would have the following at Relay T:
87CH1MT := 4 Max. Round Trip Delay for Ch 2 (OFF, 1.0–50 ms)
87CH1MD := 3 Max. Step Change in Ch 2 Delay (OFF, 3.0–50 ms)
87CH1MA := 1 Max. Allowable Asym. for Ch 2 (OFF, 0.2–10 ms)
Configure the 87L recorder to trigger for a channel alarm or a differential
operation.
87CHTRG := 87OP 87L Recording Trigger (SEL
OGIC control equation)
Many records will not be of interest, so disable write protect.
87CHWP := N Enable Write Protect 87L Recording Files (Y, N)
The data rate is 64 kb/s. A healthy channel should have a bit error rate of less
than 10
-4
, or 1 in 10000 bits. Then 262 lost packets every
40 seconds at a BER of 10
-4
, assuming uniform distribution of errors. Set the
lost packet alarm threshold at this value.
87CH1PC := 262 Ch 1 Lost Packet Alarm Thres. (OFF, 1–2500)
87CH2PC := 262 Ch 2 Lost Packet Alarm Thres. (OFF, 1–2500)
64 1024 40
10000
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