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128
Line differential protection, phase
segregated (DIFL)
6.
Inject a current in L1 and increase the current until operation in
phase L1 and L2 takes place.
The injected operation value must correspond to the set IMinOp· Ir·CT-
Factor. This value is to be read as IDiffL1 and IDiffL2, and 50% of
IDiffL1 as IBiasL1 and IBiasL2. The IDiffL3 should be zero and IBiasL3
25% of IDiffL1. These values are read on the HMI under:
Service Report/Functions/Differential/Diff Values
7.
Repeat step
6
for phase L2 and L3.
The result shall be transposed one, respectively two steps.
8.
Inject a symmetrical three-phase current, and increase the current
until operation is achieved in all three phases.
The IMinOp·Ir·CTFactor value shall be obtained for operation and read
for I
in all three phases. 100% of I
Diff
phases.
9.
Read the transmission delay on the HMI.
This command is found in the menu under:
Service value/Functions/Differential/DiffCom/ComInfo
This delay is not allowed to exceed 30ms (changed from 24 ms to 30 ms
in software revision 2p5 r03). The displayed value is 2x15 ms i.e. trans-
mission time from line end A to B + B to A.
10. Measure the operating time by injection of a single-phase current in
phase L1.
The injected current should be 4 times the operating current. The time
measurement is stopped by the trip output from the protection. The oper-
ating time should be 28-33 ms + 2 times the communication transmission
delay.
11. Disconnect the test equipment and reconnect the current transform-
er.
12. Read and check the service values of the three-phase current.
13. When the current transformers are connected, put the protection in
operation by switching off the test mode.
After the test mode is set to Off, the command must be saved to activate
the protection. The yellow LED shall stop flashing.
Verifying settings by secondary
shall be read for I
in all three
Diff
Bias
Chapter 13
injection
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