Satec Expertmeter EM720 Operation Manual page 209

Appendix E EN50160 Evaluation and Recording
Transient Overvoltages
Voltage Unbalance
EM720 Power Quality and Revenue Meter
Transient overvoltages correspond to disturbances of very
short duration, lasting typically less than one half-cycle,
i.e. a few microseconds to several milliseconds.
Method of Evaluation
Transient overvoltages are detected as impulsive or low
frequency oscillatory transients with a rise time less than
0.5 ms and duration from 20 us with the Fast Transient
coprocessor option or from 75 us without it and to ½
cycle. The impulse magnitude is evaluated by the peak
voltage value and is referenced to the nominal peak
voltage (1.414 Un). The meter can detect transient
overvoltages with a magnitude of up to 2 kV with the Fast
Transient coprocessor option or up to 700V without it.
Statistical Survey
The EM720 provides the statistical evaluation of transient
overvoltages using the classification recommended by
Eurelectric's Measurement
characteristics. Transient overvoltages are classified by
voltage magnitude as shown in Appendix D.
Indicative Values
Transient overvoltages in LV systems will generally not
exceed 6 kV peak, but higher values occur occasionally.
This characteristic defines the magnitude and/or phase
asymmetries of three-phase steady state supply voltage.
Method of Evaluation
The basic measurement is the RMS value of the steady
state voltage unbalance over a period of 10 minutes under
normal operating conditions. It is defined using the theory
of symmetrical components by the negative sequence
component expressed in percent of the positive sequence
component.
Voltage unbalance is not evaluated if the supply voltage
crosses a voltage tolerance limit (±15% Un).
Target Values
The range of voltage unbalance given in the EN50160 is:
2% ( 3% in some areas) for 95% of a week
≤ ≤
The voltage unbalance compliance limit can be changed in
the meter via the EN50160 PQ Recorder setup.
guide for voltage
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