Power Quality Analyzer PowerPad
®
IV Model 8345
125
20.2.21 Tangent
Tangent of the difference between the angle of the fundamental voltage and the
angle of the fundamental current.
Tangent, per phase:
Total tangent:
20.3 FLICKER
The quantities are calculated in accordance with class F3 of standard IEC
61000-4-15, edition 2.0, § 4.7.3, § 4.7.4, and § 4.7.5.
Flicker measures the human perception of the effects of fluctuations in the
amplitude of the voltage supplying a lamp.
These variations are caused mainly by reactive power fluctuations in the
network caused by the connection and disconnection of devices.
To accurately study the effects on vision, the measurement must be made over
a long enough time (10 minutes or 2 hours). Flicker can vary considerably over a
short period due to the different connections and disconnections to the network.
Therefore, the 8345 measures:
■
Instantaneous flicker P
inst
The value displayed is max (P
inst
) on a 150/180-cycle aggregation. The max
(P
inst
) recorded in Trend mode is calculated on the selected aggregation
■
Short-term flicker P
st
This is calculated over 10 minutes. This interval is long enough to minimize
the transient effects of connections and disconnections and long enough to
account for the deterioration of vision
■
Long-term flicker P
lt
This is calculated over 2 hours and accounts for devices with a long cycle.
For P
lt
, the instrument allows you to choose the calculation method (see
§ 3.4.1) between a fixed or sliding window. Long-term flicker is based on a
2-hour observation period
The perceived discomfort is a function of the square of the amplitude of the
fluctuation multiplied by the duration of the fluctuation. The average observer’s
sensitivity to lighting fluctuations is greatest around 10 Hz.
