P.11.25
Date Code 20151029 Protection Manual SEL-411L Relay
Testing and Troubleshooting
Checking Relay Operation
18. Confirm that the value of k and alpha is 1.0 180 at both
relays and for all three phases and no relays have operated.
19. Rotate the angle of the local current counter-clockwise until the
Q element picks up. Record this value as 1.
20. Rotate the angle of the local current clockwise until the element
drops out and picks up again. Record this value as 2.
21. Confirm that
Equation 11.9
22. For three- and four-terminal applications repeat Step 5–Step 21
using other relays as the remote terminal.
23. Repeat Step 1–Step 22 using other relays as the local terminal.
24. Use the TEST 87L command to exit Test Mode.
87L Single-Terminal
Test
Use the single-terminal test to check the characteristic of the 87L element in a
single relay. Communications with other relays is not required for this test.
For the purpose of routine maintenance, a single-terminal test carried out at
each of the relays making up the differential zone combined with a check of
the communications (see 87L Communications Report on page P.3.308) is
considered a good alternative to multiterminal testing. The test can be used for
applications that do not require charging current compensation or in-line
transformers. The test connections are shown in Figure 11.4 (refer to Test
Precautions).
Alpha Plane Test Procedure
1. Use the TEST 87L command to enter Test Mode
2. Ensure that relay outputs are supervised or isolated. See Test
Precautions for details.
3. When prompted, select a characteristic test and single-terminal
mode. Choose the A element and normal or secure depending
on the particular settings to be tested.
Pickup Check
4. Begin the test with no current injected.
5. Increase the A-phase current (simulating A-phase, local
terminal) until the A-phase element operates.
6. Confirm that the pickup value is
Equation 11.10
7. If there are two breakers at the local terminal repeat
Step 4–Step 6 using the second current input of the local relay.
Radius Check
8. Inject a current with a magnitude equal to the minimum pickup
(Step 6) into A-phase.
9. Inject a current with a magnitude equal to the minimum pickup
(Step 6) into B-phase. This simulates current at the remote
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