ABB REC670 Applications Manual page 405

1MRK 511 401-UEN A
Bay control REC670 2.2 IEC
Application manual
2
U
=
X
C
Q 1
EQUATION1871 V1 EN-US
Thereafter the current I
C
U
=
I B
C
´
3 X
C
EQUATION1872 V1 EN-US
In this way the measured LV currents can be adjusted so that the capacitor bank
current will not influence the calculation of the circulating current.
Three independent capacitor bank values Q1, Q2 and Q3 can be set for each
transformer in order to make possible switching of three steps in a capacitor bank
in one bay.
Power monitoring
The level (with sign) of active and reactive power flow through the transformer,
can be monitored. This function can be utilized for different purposes for example,
to block the voltage control function when active power is flowing from the LV
side to the HV side or to initiate switching of reactive power compensation plant,
and so on.
There are four setting parameters P>, P<, Q> and Q< with associated outputs in
TR8ATCC and TR1ATCC function blocks PGTFWD, PLTREV, QGTFWD and
QLTREV. When passing the pre-set value, the associated output will be activated
after the common time delay setting tPower.
The definition of direction of the power is such that the active power P is forward
when power flows from the HV-side to the LV-side as shown in figure 178. The
reactive power Q is forward when the total load on the LV side is inductive
( reactance) as shown in figure 178.
at the actual measured voltage U
Section 14
Control
(Equation 121)
can be calculated as:
B
(Equation 122)
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