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9.2
88
Line differential protection (DIFL)
10. Measure the operating time by injection of a single-phase cur-
rent in phase L1.
The injected current should be 4 times the operating current. The
time measurement is stopped by the trip output from the protec-
tion. The operating time should be 28-33 ms + 2 times the commu-
nication transmission delay.
11. Disconnect the test equipment and reconnect the current
transformer.
12. Read and check the service values of the three-phase current.
13. When the current transformers are connected, put the protec-
tion in operation by switching off the test mode.
After the test mode is set to Off, the command must be saved to ac-
tivate the protection. The yellow LED shall stop flashing.
14. With a through load current of minimum 20% of the Ir · CTFac-
tor , the I
and I
Diff
Bias
The I
should be lower than 10% of the actual secondary current
Diff
divided by the CTFactor, the I
This measurement is necessary at commissioning to guarantee that
there is no phase shift between the terminals.
15. Remove the external blocking of the trip signal when this test
has been successfully performed.
16. A complete commissioning or maintenance test requires that
the test is repeated at both terminals.
17. When the direct transfer trip is used, this function has to be
tested by activating its input, to check that trip is achieved at
the remote terminal. During this test, the trip circuit has to be
blocked.
Testing the charging current compensation
Procedure
1.
When the tests of the differential function have been per-
formed, set the CCComp = On and check that the settings for
XC1, XC0 and IMinOpComp are correct.
2.
Check that all currents are disconnected from the terminal
and connect symmetrical three-phase voltages to the corre-
sponding voltage input.
3.
Disconnect the voltages from the terminal and connect only
one phase to all three voltage inputs of the terminal.
are read in all phases.
should be equal to this current.
Bias
Chapter 11
Verifying settings by secondary
injection
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