GE Power Quality Meter Series User Manual

GE Power Management PQM Power Quality Meter 5-3
5 MONITORING 5.2 A1 METERING
5
NEUTRAL CURRENT
: Neutral current can be determined by two methods. One method measures the current
via the neutral CT input. The second calculates the neutral current based on the three phase currents; using
the instantaneous samples,
I
a
+ I
b
+ I
c
= I
n
. If the sum of the phase currents does not equal 0, the result is the
neutral current. When using the CT input, the neutral current reading will be correct only if the CT is wired cor-
rectly and the correct neutral CT primary value is entered. Verify neutral current by connecting a clamp-on
ammeter around all 3 phases. If the neutral current appears incorrect, check the settings in
S2 SYSTEM SETUP \
CURRENT/VOLTAGE CONFIGURATION
and verify the CT wiring.
CURRENT UNBALANCE
: Displays the percentage of current unbalance. Current unbalance is calculated as:
where:
I
av
= average phase current = ( I
a
+ I
b
+ I
c
)/3
I
m
= current in phase with maximum deviation from I
av
,
Even though it is possible to achieve unbalance greater than 100% with the above formula, the PQM
limits unbalance readings to 100%.
If the average current is below 10% of the
CT PRIMARY
setpoint, the unbalance reading is forced to 0%. This
avoids nuisance alarms when the system is lightly loaded. If the simulation currents are being used, the unbal-
ance is never forced to 0%.
Ia, Ib, Ic, In MINIMUM
: Displays the minimum current magnitudes and the time and date of their occurrence.
This information is stored in non-volatile memory and is retained during loss of control power. The
S1 PQM SETUP \ CLEAR DATA \ CLEAR MIN/MAX CURRENT VALUES
setpoint clears these values.
I U/B MINIMUM
: Displays the minimum current unbalance and the time and date of its measurement. This
information is stored in non-volatile memory and is retained during loss of control power. The
S1 PQM SETUP \ CLEAR DATA \ CLEAR MIN/MAX CURRENT VALUES
setpoint clears this value.
Ia, Ib, Ic, In MAXIMUM
: Displays the maximum current magnitudes and the time and date of their occurrence.
This information is stored in non-volatile memory and is retained during loss of control power. The
S1 PQM SETUP \ CLEAR DATA \ CLEAR MIN/MAX CURRENT VALUES
setpoint clears these values.
I U/B MAXIMUM
: Displays the maximum current unbalance and the time and date of its measurement. This
information is stored in non-volatile memory and is retained during loss of control power. The
S1 PQM SETUP \ CLEAR DATA \ CLEAR MIN/MAX CURRENT VALUES
setpoint command clears this value.
I
m
I
av
–
I
av
---------------------
100%
×
NOTE

GE Power Quality Meter Series Specifications

General

Brand	GE
Model	Power Quality Meter Series
Category	Measuring Instruments
Language	English