ABB RET670 Installation And Commissioning Manual page 197

1MRK 504 088-UEN C
Installation and commissioning manual
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.
= +
Ui UB Udi
EQUATION2090 V1 EN
9. To cause a tap change, the calculated value for circulating current voltage
adjustment must offset the injected quantity for bus voltage UB so that Ui is
outside the voltage deadband created by setting UDeadband. Expressed by
equation 24 and equation 25.
> -
Udi U 2 UB
(Equation 24)
EQUATION2092 V1 EN
=
UB Uset
(Equation 25)
EQUATION2094 V1 EN
Therfore:
× ×
Ci Icc i Xi U _
EQUATION2096 V1 EN
(
-
U 2
>
Icc i _
EQUATION2098 V1 EN
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.
Verifying settings by secondary injection
(for the purposes of this test procedure)
> -
2 Uset
)
Uset
( )
×
Ci Xi
Section 13
(Equation 23)
(Equation 26)
(Equation 27)
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