SATEC PM175 Manual - Manual (Page 98)

‎Chapter 4 PAS Application Software EN50160 Evaluation and Recording
98 Series PM175 Powermeters
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
The Plt compliance limit can be changed in the meter via the
EN50160 PQ Recorder setup.
Voltage Dips
A voltage dip is a sudden reduction of the RMS voltage below
90% of the nominal value, followed by a return to a value
higher than 90% of the nominal in a time varying from 10 ms to
60 s.
Method of Evaluation
A voltage dip is classified as one polyphase event regardless
of the shape and of the number of phases affected (as per
Eurelectric’s Application guide to the European Standard EN
50160, and 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 falls
below the start threshold on one of the phases to that at which