ABB RER670 - Page 155

Circulating current voltage regulation
SEMOD175185-775 v7
This instruction for confirmation of circulating current voltage regulation assumes
two transformers in the parallel group. Setting confirmation through secondary
injection requires calculation of circulating currents for each transformer based on
impedance values and respective compensating factors, and is therefore more
complex for greater than two transformers.
1. Confirm that OperationPAR is set to CC for the transformers in the parallel
group.
2. For parallel operation, it is also recommended that settings be confirmed for
parallel group membership, governed by setting TnRXOP in the local HMI
under Main menu/Settings/IED Settings/Control/
TransformerVoltageControl(ATCC,90)/TR8ATCC:x/ParCtrl
The general parallel arrangement of transformers are defined by setting
TnRXOP to On or Off. The following rules are applicable on the settings
T1RXOP - T4RXOP.
If IED T1 and T2 are connected,
• T1RXOP shall be set to On in instance 2 of TR8ATCC, and
• T2RXOP shall be set to On in instance 1 of TR8ATCC.
If T1 - T3 are available,
• T1RXOP and T2RXOP shall be set to On in instance 3 of TR8ATCC,
• T2RXOP and T3RXOP shall be set to On in instance 1 of TR8ATCC
and so on.
The parameter corresponding to the own IED must not be set.
T1RXOP should thus not be set in IED T1, T2RXOPnot in
IED T2 and so on.
3. Review the settings for UDeadband (based on percentage of nominal bus
voltage) and calculate the upper (U2) and lower (U1) voltage regulation limits
for which a tap change command will be issued from the master transformer
in the group.
4. Review the expected time for first (t1) and subsequent (t2) tap change
commands from the master transformer in the local HMI under Main menu/
Settings/IED Settings/TransformerVoltageControl(ATCC,90)/
TR1ATCC:x/TR8ATCC:x/Time/t1 and t2
5. Inject a voltage U
B
equal to USet 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 equal to 95% of rated load
current I2Base. This will have the effect of producing a calculated circulating
current that flows from HV to LV side for Transformer 1 and LV to HV side
for Transformer 2.
7. Confirm that a circulating current is measured on the local HMI that is equal
in magnitude to 5% of I2Base, with polarity as discussed in step
6.
8. Confirm the settings for Ci (Compensation Factor) and Xi (Transformer Short
Circuit Impedance). Using these setting values and the measured quantity of
1MRK 506 377-UEN C Section 10
Testing functionality by secondary injection
Railway application RER670 2.2 IEC 149
Commissioning manual