The normal mode BuTripMode = 1 out of 3 should have been verified in the tests above.
In applicable cases the modes 1 out of 4 and 2 out of 4 can be checked. Choose the mode
below, which corresponds to the actual case.
Checking the case
BuTripMode
=
1 out of 4
It is assumed that the ground-fault current setting Pickup_N is below phase current setting
Pickup_PH.
1. Set BuTripMode = 1 out of 4.
2. Apply the fault condition, including initiation of CCRBRF (50BF), with one-phase
current below set Pickup_PH but above Pickup_N . The residual ground-fault
should then be above set Pickup_N.
3. Verify that back-up trip is achieved after set time. If selected, re-trip should also
appear.
4. Disconnect AC and BFI_3P input signals.
Checking the case
BuTripMode
=
2 out of 4
The ground-fault current setting Pickup_N may be equal to or below phase-current setting
Pickup_PH.
1. Set BuTripMode = 2 out of 4.
2. Apply the fault condition, including initiation of CCRBRF (50BF), with one-phase
current above set Pickup_PH and residual (ground fault) above set Pickup_N.
3. Verify that back-up trip is achieved after set time. If selected, re-trip should also
appear.
4. Apply the fault condition, including initiation of CCRBRF (50BF), with at least one-
phase current below set Pickup_PH and residual (ground fault) above set Pickup_N.
The current may be arranged by feeding three- (or two-) phase currents with equal
phase angle (I0-component) below Pickup_PH, but of such value that the residual
(ground fault) current (3I
0
) will be above set value Pickup_N.
5. Verify that back-up trip is not achieved.
6. Disconnect AC and BFI_3P input signals.
11.5.8.6 Verifying instantaneous back-up trip at CB faulty condition
Applies in a case where a signal from CB supervision function regarding CB being faulty
and unable to trip is connected to input 52FAIL.
Section 11 1MRK 504 165-UUS -
Testing functionality by secondary injection
194 Transformer protection RET670 2.2 ANSI
Commissioning manual
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