Completing The Test; Line Differential Protection L3Cpdif And L6Cpdif - Hitachi RED670 Commissioning Manual

Section 11
Testing functionality by secondary injection
11.3.3.3

Completing the test

Continue to test another function or end the test by setting TESTMODE = Off. Restore connections
and settings to their original values if they were changed for testing purposes.
11.3.4

Line differential protection L3CPDIF and L6CPDIF

Prepare the IED for verification of settings as outlined in section
section
The test of the line differential protection is done with the different IEDs geographically separated
from each other. It is important to note that local actions, in one IED, may cause operation in
remotely located IEDs. In the test of the line differential function actions must be done in all involved
IEDs.
Before test the trip signal to the circuit breaker must be blocked, for example by applying the
COMBITEST test switch.
Line differential protection must be set in test mode. This involves switching the IED to Test mode
and the functions involved in the test. For the Differential protection there are settings to Test mode
and also the activation of the local function with setting "Release local". Remember also for example
the trip function block deblocking to be able to measure trip times. In the test mode the injected
current is communicated to the remote IEDs and sent back to the IED under test. The echoed current
is switched in phase 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.
Take a line with three IEDs, for example, set the return current from each remote IED to be 50% of
the injected current. Inject a current Iinjected, L1 in phase L1 to get the following differential and bias
currents:
Phase L1:
IDiff
L 1
EQUATION1458 V1 EN-US
Phase L2:
IDiff
L
EQUATION1459 V1 EN-US
Phase L3:
IDiff
L3
EQUATION1460 V2 EN-US
96
After finishing a loop test with a line-in service, and before leaving the test mode,
ReleaseLocal must be set to BlockAll on the local HMI under Main menu /Test /Line
differential test /LineDiffLogic . If not done, the load current may cause incorrect
L4CPDIF operation when the IED is restarted.
"Preparing for test" in this chapter.
When the protection at one end is activated to Test mode, this information is
automatically sent to remote end IEDs through the LineDiffLogic function block and
the remote functions are then also blocked automatically.
= =
IBias I
L 1 injected L , 1
= =
IBias I
2 L 2 injected L , 1
= IBias = 0
L3
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"Requirements" and
Line differential protection RED670
Commissioning manual
SEMOD56264-55 v6