4.19
Date Code 20090730 Instruction Manual SEL-734 Meter
Metering
Harmonic Metering
Harmonic Metering
The SEL-734 provides harmonic measurements for the following values:
➤ Harmonic magnitudes for voltage, current, and power
➤ Harmonic angles for voltage and current
➤ Percent of fundamental harmonic magnitudes for voltage and
current
The 0734P model provides harmonic measurements up to the 50th order. The
07340 model provides harmonic measurements up to the 15th order. Both
models provide SEL
OGIC harmonic threshold alarms for the 2nd through the
15th harmonic order.
Harmonic Percentage Harmonics from the second to fifteenth are converted into a percentage of the
fundamental and compared to the threshold (HARM02 to HARM15). If the
threshold is enabled and the harmonic is above the set threshold, then the
respective harmonic Meter Word bit (HARM02 to HARM15) asserts. The bit
will deassert when the respective harmonic falls below the set threshold.
Harmonics for currents and voltages are calculated on a per-phase basis; any
single-phase harmonic value asserts the HARM02–HARM15 Meter Word
bits. If any harmonic Meter Word bit is set, then the FALARM (frequency
alarm) Meter Word bit is set.
If the given harmonic threshold is exceeded, the meter Meter Word bit will
assert (logical 1).
EXAMPLE 4.1 Harmonic Alarm Example
Suppose that you had noticed that approximately once a month the
system experienced a power failure. The cause was believed to be the
starting of some large loads that induced harmonics into the system,
but this was not verified. With the SEL-734, you made the following
settings:
SET HARM02 = 10
HARM03 = 10
•
•
•
HARM07 = 10
SET L OUT101 = HARM02 OR HARM03 OR HARM04 OR HARM05
OR HARM06 OR HARM07
SET R SER1 = HARM02, HARM03, HARM04, HARM05, HARM06,
HARM07
You then monitored OUT101 via the SCADA system and noticed that
every time a certain load was started, the 3
rd
harmonic was
generated in significant levels.
Harmonic Magnitudes The SEL-734 calculates and updates harmonics as absolute magnitudes once
every four seconds. The MET H M command displays the Harmonic
Magnitude report. Reported currents and voltages range from 0.00–22.00
amps secondary and 0.00–300.00 volts secondary, respectively. Form 9 and
Form 5 reports are identical, except that all entries in the IB and VB columns
are filled with zeroes.
Courtesy of NationalSwitchgear.com
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