GE PQMII Instruction Manual page 128

5–44
advantageous to compensate for low (lagging) power factor values by connecting a
capacitor bank to the circuit when required. The PQMII provides power factor monitoring
and allows two stages of capacitance switching for power factor compensation.
The PQMII calculates the average power factor in the three phases, according to the
following equation:
Average Power Factor
Two independent 'elements' are available for monitoring power factor, Power Factor 1 and
Power Factor 2, each having a pickup and a dropout level. For each element, when the
measured power factor is equal to or becomes more lagging than the pickup level (i.e.
numerically less than), the PQMII will operate a user-selected output relay. This output can
be used to control a switching device which connects capacitance to the circuit, or to
signal an alarm to the system operator. After entering this state, when the power factor
becomes less lagging than the power factor dropout level, the PQMII will reset the output
relay to the non-operated state.
Both Power Factor 1 and 2 features are inhibited from operating unless all three voltages
are above 20% of nominal and one or more currents is above 0. Power factor 1 and 2 delay
timers will be allowed to time only when the 20% threshold is exceeded on all phases (and,
of course, only while the power factor remains outside of the programmed pickup and
dropout levels). In the same way, when a power factor condition starts the power factor 1
or 2 delay timer, if all three phase voltages fall below the 20% threshold before the timer
has timed-out, the element will reset without operating. A loss of voltage during any state
will return both Power Factor 1 and 2 to the reset state.
• POWER FACTOR LEAD 1(2) RELAY: Power factor detection can either be disabled, used
as an alarm or as a process control. Set this setpoint to "Off" if the feature is not
required. Selecting "Alarm" activates the alarm relay and displays an alarm message
when the power factor is more leading than the level set. Selecting "Aux1", "Aux2", or
"Aux3" activates the respective auxiliary relay when the power factor is equal to or
more leading than the level set, but no message will be displayed. This is intended for
FIGURE 5–5: Capacitor Bank Switching
Total 3-phase Real Power
= ----------------------------------------------------------------------------
Total 3-phase Apparent Power
PQMII POWER QUALITY METER – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
(EQ 5.2)