Hitachi RET670 Commissioning Manual page 253

1MRK 504 165-UEN Rev. K
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(90, U↕)/TR8ATCC(90, U↕||):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,
•
•
If T1 - T3 are available,
•
•
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(90, U↕) /TR1ATCC(90, U↕):x/TR8ATCC(90, U↕||):x /Time/t1 and
t2
5. Inject a voltage U
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 circulating current from
the local HMI (Icc_i), calculate the value for circulating current voltage adjustment Uci.
Udi
EQUATION2088 V1 EN-US
The voltage regulation algorithm then increases (for transformer T2) or decreases (for
transformer T1) the measured voltage by Udi and compares Ui against the voltage deadband
limits U1 and U2 for the purposes of voltage regulation.
EQUATION2090 V3 EN-US
9. To cause a tap change, the calculated value for circulating current voltage adjustment must
offset the injected quantity for bus voltage U
created by setting UDeadband. Expressed by equation
Transformer protection RET670
Commissioning manual
T1RXOP shall be set to On in instance 2 of TR8ATCC, and
T2RXOP shall be set to On in instance 1 of TR8ATCC.
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.
equal to USet for each transformer.
B
= × ×
Ci Icc i Xi _
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Testing functionality by secondary injection
so that Ui is outside the voltage deadband
B
127 and equation 128.
Section 11
(Equation 125)
(Equation 126)
247