Schweitzer Engineering Laboratories SEL-734W, Справочник по полевым условиям эксплуатации

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6.2
SEL-734W and SEL Wireless Current Sensor Field Reference Guide Date Code 20191029
Differences Between the SEL-734B and the SEL-734W
Metering
Metering
Both the SEL-734B and SEL-734W use the same calculation method to compute
metering quantities. The quantities include instantaneous, demand, energy, maxi-
mum and minimum, crest factor, and harmonics. The metering data provided by
both the SEL-734B and SEL-734W can be different whenever the SEL-734W
has an update and the current has changed since the last update. The SEL-734B
can capture more transient behavior than the SEL-734W. For a smooth load cur-
rent, it is expected that both the SEL-734B and SEL-734W have similar metering
quantities.
Power Quality and Event Analysis
Because of the metering data differences between the SEL-734B and SEL-734W,
the power quality given by them are different. SEL does not recommend that the
SEL-734W be used as a revenue meter or a device that you expect to capture
quick changes or transients.
Both the SEL-734B and SEL-734W use the same methods and techniques to
generate event reports. The reports include waveform capture event reports,
Sequential Event Recorder (SER) reports, and voltage sag/swell/interruption
(VSSI) reports. See
Section 6 in the SEL-734 Instruction Manual for details.
Waveform Capture Event Reports
Waveform capture, also known as oscillography, allows the SEL-734W to record
the voltage and current waveforms associated with programmable trigger condi-
tions, such as a voltage interruption. The sample rate and duration of the wave-
form capture are predetermined by using Event Report settings. The supported
sample rate is 1 kHz. The 1 kHz sample rate contains harmonic content as far as
the 7th order.
The duration of the waveform capture can be set to 0.25 seconds or 15 cycles for
a 60 Hz system. Each waveform capture contains at least 4 cycles of pretriggered
data.
Although the SEL-734W can capture waveforms for 0.25 seconds, the measured
current waveform will likely remain constant during this interval because of the
SEL-734W update rates. It is possible to see a jump in the captured current wave-
forms if the SEL-WCS provides an update of the current values during this 0.25
second interval.
Sequence of Events (SOE) Report
Users program conditions (known as trigger settings) under which values are
logged to the Sequence of Events (SOE) report. If the line current is used as part
of a trigger setting, the trigger may be delayed based on when the SEL-WCS
update is received. If a transient in the current does not last long enough to be
captured by the SEL-WCS, no event capture will happen. For an event capture
that is triggered, the line current reported may not be the line current at the time
of the event. Keep these differences in mind when using the SEL-734W SER
reports for forensic analysis.