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Users Manual
36
Formula for Plt Function
3
12
1
3
12
∑
=
=
i
Pst
Plt
Time
Flicker [%]
Interval length => 1 Pst
12 x interval length => 1 flicker value Plt
egb020.eps
Figure 17. Measuring Flicker Values
Unbalance
The ratio of negative-to-positive sequence harmonics is calculated, with the
angles and magnitudes of the phase voltages taken into account. These values
are averaged over the interval length defined in PQ Log.
Frequency
The line power frequency is measured and averaged over 10 seconds, and the
resulting values are divided into 42 classes for establishing statistics. Values
are also averaged over the interval length defined in PQ Log.