ABB RET670 Commissioning Manual page 252

Section 11
Testing functionality by secondary injection
246
The voltage injection equal to USet 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 On 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.
5. Inject a voltage U
B
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 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 U
B
(USet – (VTmismatch · USet)) 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 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 responds in accordance with the setting for CircCurrBk.
equal to USet for each transformer.
equal to USet for Transformer 1 and a voltage less than
1MRK 504 165-UEN A
SEMOD175185-841 v6
SEMOD175185-859 v4
Transformer protection RET670 2.2 IEC
Commissioning manual