E-Mon E-PS-A-RTU-N - Manual (Page 91)

Chapter 4 Power
S O F T W A R E E N 5 0 1 6 0 E V A L U A T I O N A N D
R E C O R D I N G
PowerSmart+ Advanced Power Quality Meter 91
Method of Evaluation
A temporary overvoltage is classified as one polyphase event regardless of the shape and
of the number of phases affected (as per IEC 61000-4-30). An event can begin on one
phase and end on another phase. The fault magnitude is recorded separately for each
phase involved. The event duration is measured from the instant at which the voltage rises
above the start threshold on one of the phases to that at which it becomes lower than the
end threshold on all affected phases including a threshold hysteresis.
The overvoltage threshold can be changed in the meter via the EN50160 PQ Recorder
setup.
The basic voltage measurement is one-cycle RMS voltage updated each half-cycle.
Statistical Survey
The PowerSmart+ Advanced PQM provides the statistical evaluation of temporary
overvoltages using the classification recommended by Eurelectric’s Measurement guide for
voltage characteristics. Temporary overvoltages are classified by voltage magnitude and
duration as shown in Appendix E.
Indicative Values
Temporary overvoltages on the low voltage side will generally not exceed 1.5 kV RMS.
Transient Overvoltages
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 transients with a rise time less than 0.5
ms and duration from 150 us 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 700V.
Statistical Survey
The PowerSmart+ Advanced PQM provides the statistical evaluation of transient
overvoltages using the classification recommended by Eurelectric’s Measurement guide for
voltage characteristics. Transient overvoltages are classified by voltage magnitude as
shown in Appendix E.
Indicative Values
Transient overvoltages in LV systems will generally not exceed 6 kV peak, but higher
values occur occasionally.
Voltage Unbalance
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.