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1MRK 505 378-UEN Rev. K
11.3.4.1
Verifying the settings
Procedure
1.
Block the trip signal from all involved IEDs with local operation released. See below.
2.
Set Test mode to On for the Line differential function for test.
3.
Release the local function with setting ReleaseLocal in local HMI under: Main menu /Test /
Line differential test /LineDiffLogic
4.
Set the factor of the return currents to 1/(number of current IEDs = 1).
5.
Inject a current in phase L1 and increase the current until the function operates for phases L1
and L2.
The injected operate current must correspond to the set IdMin. The service values for IDiffL1,
IBiasL1, IDiffL2 and IBiasL2 must be equal to the injected current.
6.
Repeat step
7.
Inject a symmetrical three-phase current, and increase the current until operation is achieved in
all three phases.
The injected operate current must correspond to the set IdMin. The service values for IDiffL1,
IBiasL1, IDiffL2, IBiasL3, IDiffL3 and IBiasL3 must be equal to the injected current.
8.
Read the transmission delay.
9.
Measure the operating time by injection of a single-phase current in phase 1.
The injected current must be 4 times the operating current. The time measurement is stopped
by the trip output.
Note that tripping times at this loop test includes sending the local currents to remote side and
with a factor sending them back. This means that tripping times are virtually double to the times
achieved at a real fault or at bench testing.
10.
Check the negative sequence fault discriminator by injecting a three-phase current with
changed phase sequence: switch phases L1 and L2. The injected current will now be seen as a
pure negative-sequence current where the phase angle between the local negative-sequence
current and the remote negative-sequence currents will be 120°.
With the current above IMinNegSeq, the signal external fault (EXTFAULT) must apply. No trip
must be generated.
11.
Disconnect the test equipment and reconnect the current transformers.
12.
Read and check the service values of the three-phase current.
13.
Switch off the test mode and the release local.
14.
With a through load current (maximum current of line ends) of minimum 20% of IBase the
current IDiff and IBias are read in all phases.
IDiff must be less than 10% of the maximum line end current and IBias must be equal to the
largest line end current.
11.3.4.2
Completing the test
Continue to test another function or end the test by changing the TESTMODE setting to Off. Restore
connections and settings to the original values, if changed for testing purposes.
11.3.5
Additional security logic for differential protection LDRGFC
11.3.5.1
Verifying the settings
Line differential protection RED670
Commissioning manual
4
by current injection in phases L2 and L3.
After finishing a loop test with line in service and before leaving test mode, the
setting ReleaseLocal in local HMI under: Main menu /Test /Line differential
test /LineDiffLogic must be set to BlockAll. If not, the load current might cause
incorrect operation of the differential function at restarts of the line differential
protection IED.
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Section 11
Testing functionality by secondary injection
SEMOD56264-69 v4
SEMOD56264-104 v5
GUID-0E064528-0E70-4FA1-87C7-581DADC1EB55 v2
GUID-D9F626D4-4038-416F-888E-D3DB5047E79A v1
97
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