Satec Expertmeter EM720 Operation Manual page 205

Appendix E EN50160 Evaluation and Recording
Frequency Variations
Supply Voltage Variations
Rapid Voltage Changes
EM720 Power Quality and Revenue Meter
Method of Evaluation
The basic frequency measurement is the mean value of
the frequency over fixed time intervals of 10 seconds
under normal operating conditions.
A frequency variation is not evaluated if the supply
voltage crosses a voltage tolerance limit (±15% Un).
Target Values
The ranges of frequency variations given in the EN50160
are:
• 50Hz±1% for 95% of a week
• 50Hz±1% for 99.5% of a year
• 50Hz+4/-6% for 100% of the time
The same limits are used for 60Hz systems. The frequency
compliance limit can be programmed in the meter in
percent of the nominal power frequency via the EN50160
PQ Recorder setup.
This characteristic defines slow variations of steady state
supply voltage magnitude.
Method of Evaluation
The basic supply voltage magnitude measurement is the
RMS value of the steady state voltage over a period of 10
minutes under normal operating conditions.
A voltage variation is not evaluated if the supply voltage
crosses a voltage tolerance limit (±15% Un).
Target Values
The range of voltage variations given in the EN50160 is:
±10% Un for 95% of a week
The supply voltage compliance limit can be changed in the
meter via the EN50160 PQ Recorder setup.
Rapid voltage changes are sudden but relatively weak
voltage variations between two steady state voltage
levels.
Method of Evaluation
Evaluation of rapid voltage changes is made on an hourly
basis. The RMS voltage is evaluated over 1-second time
integration intervals. The meter establishes the maximum
difference of the RMS voltage between two intervals
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