Hitachi Relion 670 Series Commissioning Manual page 182

Section 11
Testing functionality by secondary injection
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
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.
176
= × ×
Ci Icc i Xi _
(Equation 47)
(Equation 48)
× × > -
_ 2
( )
-
U 2 Uset
>
_
(
Ci Xi
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so that Ui is outside the voltage deadband
B
(for the purposes of this test procedure)
Uset
)
×
1MRK 511 403-UEN Rev. L
47 and equation 48.
Bay control REC670
Commissioning manual
(Equation 45)
(Equation 46)
(Equation 49)
(Equation 50)