SATEC EM920 Operation Manual - Manual (Page 22)

Chapter 2 Operating the EM920
Demand Forgiveness (Cold Load Pickup)
22 EM920 Power Quality and Revenue Meter
Voltage and current harmonic measurements are based on
10-cycle/50Hz or 12-cycle/60Hz waveforms (per
IEC 61000-4-7), sampled at a rate of 128 samples/cycle. The
EM920 uses dynamic sampling techniques to maintain a
steady sampling rate and avoid instrumentation errors when
the line frequency changes.
The meter provides short and long term flicker
measurements as per IEC 61000-4-15.
The following table shows time-aggregation intervals
available for different RMS and power quantities.
Parameter 1/2
cycle
1
cycle
200 ms 1
sec
3 sec 10
sec
10
min
2
hours
RMS volts Ч Ч Ч Ч Ч Ч Ч
RMS currents Ч Ч Ч Ч 1 Ч Ч Ч
Powers Ч 3 Ч 1
Zero-sequence Ч Ч Ч Ч Ч Ч Ч
Unbalance Ч Ч Ч Ч Ч Ч
Frequency Ч Ч Ч Ч Ч
Total harmonics Ч Ч Ч Ч Ч
Total interharmonics Ч Ч Ч
Individual harmonics Ч Ч 2
Individual interharmonics Ч Ч 2
K-factor Ч Ч Ч Ч Ч
Flicker Ч Ч
Symmetrical components Ч Ч
Phasors ×
1 Taken from the energy measurement channel
2 Only for power quality evaluation
3 Not affected by loss compensation
Demand Forgiveness (Cold Load Pickup)
Demand forgiveness (sometimes called cold load pickup)
avoids recording abnormal maximum demands in installations
with high pickup currents. Demand forgiveness is the time
during which the meter does not calculate or store the
maximum demands after a power outage.
The demand forgiveness time and the minimum outage
duration to be qualified for demand forgiveness are
programmable in the meter.
See Device Options and Mode Control in Chapter 5 on how to
program these settings in your meter.
Instrument Transformer Correction
Ratio and phase angle error correction can be applied to
external CTs and PTs to achieve overall metering installation
accuracy, or be used in any metering installation to optimize
the accuracy of the metering data.
The user can program up to 8 test points for both ratio
correction and phase angle error curves covering the typical
transformer operating range.