P.11.24
SEL-411L Relay Protection Manual Date Code 20151029
Testing and Troubleshooting
Checking Relay Operation
87LG
1. For this test, the same current is applied to all three current
inputs of the relay (pure zero-sequence) in order to exercise all
three of the relay inputs.
2. Use the TEST 87L command to enter Test Mode.
3. Ensure that relay outputs are supervised or isolated. See Test
Precautions for details.
4. When prompted, select a characteristic test and multiterminal
mode. Choose the G element and normal or secure depending
on the particular settings to be tested.
Pickup Check
5. Begin the test with no current injected at any terminal.
6. Inject a zero-sequence current at the local terminal. Increase the
magnitude until the G element operates.
7. Confirm that the pickup value is
Equation 11.7
8. Confirm that each of the remote relays also operates.
9. If there are two breakers at the local terminal, repeat
Step 5–Step 8 using the second current input of the local relay.
Radius Check
10. Inject a zero-sequence current with a magnitude equal to the
minimum pickup (Step 7) into the local terminal.
11. Inject a zero-sequence current with a magnitude equal to the
minimum pickup (Step 7) into a remote terminal. Adjust the
phase angle at this terminal to be 180 degrees out-of-phase with
the local terminal current.
12. Confirm that the G element is picked up.
13. Increase the local current until the element drops out.
14. Confirm that the dropout current is
Equation 11.8
15. If there are two breakers at the remote terminal, repeat
Step 10–Step 14 using the second current input of the remote
relay.
Blocking Angle Check
16. Inject a zero-sequence current with a magnitude equal to the
minimum pickup (Step 7) at the local terminal.
17. Inject a zero-sequence current with a magnitude equal to the
minimum pickup (Step 7) at a remote terminal. Adjust the
phase angle at this terminal to be 180 degrees out-of-phase with
the local terminal.
I
DROPOUT
Tap
1
87LGR S
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