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Section 11
Testing functionality by secondary injection
EQUATION2092 V2 EN-US
EQUATION2094 V2 EN-US
Therfore:
Ci Icc i Xi U
EQUATION2096 V1 EN-US
Icc i
EQUATION2098 V1 EN-US
10.
Using the settings for USet, UDeadband, C (Compensating factor) and Xr2 (transformer short
circuit impedance) calculate the magnitude of Icc_i necessary to cause a tap change
command.
11.
Inject current equal to I2Base for Transformer 1 and (I2Base - |Icc_i|) for Transformer 2 so that
the magnitude of calculated circulating current will cause a raise command to be issued for
Transformer 2 and a lower command for Transformer 1. Magnitude and direction of circulating
currents measured for each 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.
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
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
248
(Equation 127)
(Equation 128)
×
×
>
-
_
2
(
)
-
U
2
Uset
>
_
(
Ci Xi
The voltage injection equal to USet is required for both transformers during this test.
equal to USet for each transformer.
B
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(for the purposes of this test procedure)
Uset
)
×
1MRK 504 165-UEN Rev. K
(Equation 129)
(Equation 130)
SEMOD175185-841 v6
SEMOD175185-859 v4
Transformer protection RET670
Commissioning manual
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