ABB REG670 Applications Manual page 573

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
U
=
I B
C
´
3 X
C
EQUATION1872 V1 EN
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 290. The reactive
power Q is forward when the total load on the LV side is inductive ( reactance) as
shown in figure 290.
HV-side
Pforward
Qforward
(inductive)
LV-side
IEC06000536 V2 EN
Figure 290: Power direction references
With the four outputs in the function block available, it is possible to do more than just
supervise a level of power flow in one direction. By combining the outputs with
logical elements in application configuration, it is also possible to cover for example,
intervals as well as areas in the P-Q plane.
IED
ATCC
IEC06000536_1_en.vsd
Section 15
Control
(Equation 275)
567