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Section 11
Testing functionality by secondary injection
1.
Connect the test set for single-phase current injection to the protection terminals connected to
the CT in the power transformer neutral-to-earth circuit.
2.
Increase the injection current and note the operating value of the protection function.
3.
Check that all trip and start signals appear according to the configuration logic.
4.
Decrease the current slowly from operate value and note the reset value.
5.
Connect the timer and set the current to ten times the value of the IdMin setting.
6.
Switch on the current and note the operate time.
7.
Connect the test set to terminal L1 and neutral of the three-phase current input configured to
REFPDIF. Also inject a current higher than half the IdMin setting in the neutral-to-earth circuit
with the same phase angle and with polarity corresponding to an internal fault.
8.
Inject current into terminals L2 and L3 in the same way as in step 7 above and note the operate
and reset values.
9.
Inject a current equal to 10% of rated current into terminal L1.
10.
Inject a current in the neutral-to-earth circuit with the same phase angle and with polarity
corresponding to an external fault.
11.
Finally check that trip information is stored in the event and disturbance recorder.
11.3.2.3
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.
11.3.3
Line differential protection L4CPDIF
Prepare the IED for verification of settings outlined in Section
The Line differential protection function (L4CPDIF) is tested with different IEDs geographically
separated from each other. Local actions in one IED may cause operation in remote IEDs, and this is
why testing actions must be performed in all involved IEDs.
Before testing the L4CPDIF function, the trip signal to the circuit breaker must be blocked, for
example, by applying the COMBITEST test switch.
The IED and all functions involved in the test must be set to test mode. The local function is activated
with setting ReleaseLocal. The trip function block must be deblocked so that trip times can be
measured.
In test mode, the injected current is communicated to the remote IEDs and then sent back to the IED
under testing. The echoed current is switched in phases so that current in phase L1 is returned in
phase L2, current in phase L2 is returned in phase L3 and current in phase L3 is returned in phase
L1. The amplitude of the returned current can be set separately as a ratio of the injected current. For
example, in a line with three IEDs the return current from each remote IED is set to 50% of the
injected current. Current I
currents:
Phase L1:
IDiff
L
1
EQUATION1458 V1 EN-US
Phase L2:
94
When the L4CPDIF function in a local IED is set to test mode, information on this is
automatically sent to IEDs at remote ends. The L4CPDIF functions at remote end
IEDs are then also blocked automatically.
injected, L1
=
=
IBias
I
L
1
injected L
, 1
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is injected in phase L1 to get the following differential and bias
1MRK 505 378-UEN Rev. K
GUID-3B2CCAFF-38B2-4C16-94F9-88B7D4B6F2B3 v2
"Preparing the IED to verify
Line differential protection RED670
Commissioning manual
SEMOD55252-118 v5
settings".
(Equation 1)
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