SATEC EM720 Operation Manual - Manual (Page 21)

Chapter 2 Operating the EM720
Instrument Transformer Correction
EM720 Power Quality and Revenue Meter 21
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
EM720 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
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.
The EM720 is able to calculate the transformer errors
dynamically based on the transformer performance
characteristics and the actual CT current and PT voltage
signals appearing at the meter, to interpolate to the actual
measured operating point and to apply the interpolated error
corrections to the meter calculations.
See Instrument Transformer Correction Setup on how to
program the ratio correction factors and phase angle errors
for external CTs and PTs and enable correction in the meter.
See
Device Options and Mode Control on how to enable and
disable correction in the meter via the front display.