transformer can be observed as service values on the local HMI and raise/lower
commands detected from the binary output mapped in the Signal Matrix.
The voltage injection equal to VSet is required for both transformers
during this test.
12. Confirm that a tap change command is issued from the voltage control function to
compensate for the circulating current.
13. Injected currents can be reversed such that the direction of calculated circulating
currents change polarity, which will cause a lower command for Transformer 2 and
a raise command for Transformer 1.
Circulating current limit
1. Confirm that OperationPAR is set to CC for each transformer in the parallel group.
2. Confirm that OperCCBlock is set to Enable for each transformer in the parallel
group.
3. Review the setting for CircCurrLimit.
4. Review the setting for CircCurrBk to confirm whether a circulating current limit will
result in an Alarm state, Auto Block or Auto&Man Block of the automatic voltage
control for tap changer, for parallel control function TR8ATCC (90).
5. Inject a voltage V
B
equal to VSet for each transformer.
6. Inject a load current for Transformer 1 that is equal to rated load current I2Base and
a load current for Transformer 2 that is 1% less than (I2Base – (I2Base ·
CircCurrLimit))
7. Confirm that the automatic voltage control for tap changer, for parallel control
function TR8ATCC (90) responds in accordance with the setting for CircCurrBk.
Alarm and blocking conditions can be confirmed through interrogation of the event
menu or the control menu on the local HMI.
VTmismatch
during parallel operation
1. Confirm that OperationPAR is set to MF for each transformer in the parallel group.
2. Review the setting for VTmismatch and tVTmismatch.
3. Inject a voltage V
B
equal to VSet for Transformer 1 and a voltage less than (VSet –
(VTmismatch · VSet)) for Transformer 2.
4. This condition should result in a VTmismatch which will mutually block the
operation of the automatic voltage control for tap changer, parallel control function
TR8ATCC (90) for all transformers connected in the parallel group, which can be
confirmed through interrogation of the local HMI.
5. Confirm that the automatic voltage control for tap changer, parallel control function
TR8ATCC (90) responds in accordance with the setting for CircCurrBk.
1MRK 504 165-UUS - Section 11
Testing functionality by secondary injection
Transformer protection RET670 2.2 ANSI 257
Commissioning manual
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