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,
• 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, T2RXOP not in
IED T2, and so on.
3. The lowest transformer number in the parallel group is by default set as the
Master
– confirm that this is the case by reviewing the setting in the local HMI.
4. 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.
5. 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/Setting group N/Control/TransformerVoltageControl(ATCC,
90)/VCSx/VCPx/Time/t1 and t2
6. Apply a voltage 1% below U1 and wait for the issue of a raise command from
the voltage control after the expiry of a constant or inverse time delay set by
t1. Detection of this command will involve locating the allocated binary
output for a raise command in the Signal Matrix in PCM600 and monitoring a
positive from this output. Confirm the timing of this command correlates with
the setting t1.
7. After the issue of the raise command, confirm that all follower transformers
in the group change tap in accordance with the command issued from the
master transformer.
8. Inject a voltage UB for the master transformer that is 1% above the upper
deadband limit U2 and wait for the issue of a lower command from the
voltage control after the expiry of a constant or inverse time delay set by t2.
9. Confirm that all follower transformers in the group change tap in accordance
with this command.
Circulating current voltage regulation
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.
1MRK 504 088-UEN C Section 13
Verifying settings by secondary injection
189
Installation and commissioning manual
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