Instrument description | 15
FRAKO | Operating Manual | Power Quality Controller – PQC
4
Instrument description
4.1
Function
The PQC Power Quality Controller continuously calculates the reactive and active
power components in the supply network using the measurement data from the cur-
rent path (current transformer) and the voltage path (voltage measurement connec-
tion). If the reactive power component exceeds certain thresholds, which the PQC has
determined during the calibration procedure or which have been set as described,
switching commands are given via the instrument outputs. If the inductive reactive
power is greater than the value preset during instrument configuration (target cos
φ
),
after an adjustable time delay one or more of the PQC control contacts are closed.
The PQC thus switches capacitor stages in as required in order to restore the target
power factor. If the inductive reactive power component of the loads reduces again,
this causes capacitor stages to be switched out. The PQC makes a variety of options
possible for customizing the control settings to suit the individual application. The
clear overview in the display provides effective monitoring of power factor correction.
So-called ‘cyclic switching’ is a useful feature for prolonging the service life of the
installation, since it ensures that all capacitor stages of the same power rating are on
average switched in equally frequently.
Regeneration
The PQC has a four-quadrant control function. If active power is fed back into the sup-
ply network, for example by combined heat and power systems, the PQC continues to
correct for the reactive power drawn from the supply network. When this regeneration
occurs, the active power P is displayed with a minus sign before it. Regeneration
mode is also indicated by a symbol appearing on the display screen.