E-Mon E-PS-A-RTU-N - Manual (Page 89)

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 89
Supply Voltage Variations
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
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 3-second time integration intervals. The meter establishes the maximum
difference of the RMS voltage between two intervals selected from three 3-second
consecutive intervals and compares it with the target compliance limit.
A rapid voltage change is not classified if it crosses a voltage tolerance limit (±10% Un), as
it would be considered a voltage dip or a temporary overvoltage.
Target Values
The maximum rate of rapid voltage changes in normally once per hour or less. For voltage
variations repeating more than once an hour, amplitude is limited by the flicker index. The
maximum rate of rapid voltage changes in variations per hour can be changed in the meter
via the EN50160 Advanced Setup. The target magnitude limit of rapid voltage changes can
be programmed in the meter via the EN50160 PQ Recorder setup.
Under usual operating conditions the magnitude of rapid voltage changes (once per hour or
less) should generally not exceed 5% of nominal voltage in LV networks, and 4% in MV
networks. In some circumstances, like in systems where equipment switching must be
carried out to meet supply system or load requirements, it can reach 10%Un in LV
networks, and 6%Un in MV networks.
Flicker
Flicker expresses the visual discomfort caused by repetitive changes of brightness in
lightning subjected to fluctuations of the supply voltage. Flicker is indicated by the long-
term flicker severity parameter Plt, which is evaluated every 2 hours.
Method of Evaluation
The basic measurement is the short-term flicker severity indicator Pst, evaluated each 10
minutes by instrumentation complying with IEC 61000-4-15. The indicative long-term flicker
severity Plt is evaluated from 12 consecutive Pst values. For testing purposes, the Pst
period can be temporarily changed in the meter in the range of 1 to 10 minutes via the
EN50160 Advanced Setup.
Pst values are not classified during intervals when the supply voltage magnitude exceeds a
voltage tolerance limit (±15% Un) or is affected by voltage dips with depth more than 15%
Un.
Target Values
The flicker compliance limit given in the EN50160 is:
Plt ≤ 1 for 95% of a week