GE 750 User Manual

13-
4
750/760 Feeder Management Relay GE Power Management
13.2 POWER FACTOR 13 S6 MONITORING
13
13.2 POWER FACTOR 13.2.1 DESCRIPTION
It is generally desirable for a system operator to maintain the power factor as close to unity as possible to min-
imize both costs and voltage excursions. Since the power factor is variable on common non-dedicated circuits,
it is advantageous to compensate for low (lagging) power factor values by connecting a capacitor bank to the
circuit when required. The relay allows two stages of capacitance switching for power factor compensation.
Figure 13–3: CAPACITOR BANK SWITCHING
The relay calculates the average power factor in the three phases, according to the following equation.
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 becomes more
lagging than the pickup level (i.e. numerically less than), the relay will operate a user-selected output contact.
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 for a time larger than the set delay, the relay will reset the output contact to the non-
operated state.
Both
POWER FACTOR 1
and
2
features are inhibited from operating unless all three voltages are above 30% of
nominal and one or more currents is above 0.
POWER FACTOR 1
and
2
delay timers will only be allowed to time
when the 30% threshold is exceeded on all phases and 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 30% 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.
1.00
0.90
0.95
0.85
POWER F
ACT
OR
(+) lagging
leading (-)
POWER
FACTOR 1
DELAY
POWER
FACTOR 2
DELAY
POWER FACTOR 1
DROPOUT
POWER FACTOR 2
DROPOUT
POWER FACTOR 1
PICKUP
SW
ITCH
CAP
ACIT
O
R 1
IN CIRCU
IT
POWER FACTOR 2
PICKUP
SW
ITC
H
CAP
ACIT
O
R 2
IN CIRCUIT
SW
ITCH
CAP
ACIT
O
R 2
O
UT O
F CIRCUI
T
SW
ITCH
CAP
ACIT
O
R
1
O
U
T O
F CIRC
UI
T
Average Power Factor =
Total 3 Phase Real Power
Total 3 Phase Apparent Power

GE 750 Specifications

General

Brand	GE
Model	750
Category	Relays
Language	English