Doc# E107706 12- 3
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12: Flicker and Analysis
P(3s) = (P(2.2) + P(3) + P(4))/3
P(10s) = (P(6) + P(8) + P(10) + P(13) + P(17))/5
P(50s) = (P(30) + P(50) + P(80))/3
The .3-second memory time constant in the Flicker meter ensures that P(0.1) can-
not change abruptly and no smoothing is needed for this percentile.
• Long Term Flicker Evaluation: The 10-minute period on which the short-term Flicker
severity is based is suitable for short duty cycle disturbances. For Flicker sources
with long and variable duty cycles (e.g. arc furnaces) it is necessary to provide cri-
teria for long-term assessment. For this purpose, the long-term Plt is derived from
the short-term values over an appropriate period. By definition, this is 12 short-
term values of 10 minutes each over a period of 2 hours. The following formula is
used:
where Psti (i = 1, 2, 3, ...) are consecutive readings of the short-term severity Pst.
12.2.1: Summary
Flicker is changes in the illumination of light sources due to cyclical voltage
variations.
Pinst is Instantaneous Flicker values in Perceptibility Units (PU).
Pst is value based on 10-minute analysis.
Plt is value based on 12 Pst values.
Measurement Procedure
1. Original Signal with amplitude variations
2. Square demodulator
3. Weighted filter
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