ABB ret650, Руководство по применению, Страница: 216 / 392

2
1
C
U
X
Q
=
EQUATION1871 V1 EN-US
(Equation 52)
Thereafter the current I
C
at the actual measured voltage U
B
can be calculated as:
3
B
C
C
U
I
X
=
´
EQUATION1872 V1 EN-US
(Equation 53)
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
SEMOD159053-251 v4
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
79 . The
reactive power Q is forward when the total load on the LV side is inductive
( reactance) as shown in figure
79 .
Section 11
1MRK 504 169-UEN A
Control
210 Transformer protection RET650 2.2 IEC
Application manual