Environmental Engineering Reference
In-Depth Information
F
≤
1 is the shape factor of the voltage change waveform.
The flicker strength
P
st
is the sum of the flicker impressions within a time interval
T
p
. When
F
is taken as 1, and
T
p
is chosen as 10 min (600 s), the short-time flicker
strength is calculated
P
st
=
1
/
3
,
2
∑
t
f
T
p
(7.6)
According to EN 50160 the value
P
st
= 1 must not be exceeded in 95% of a week
observation interval.
Flickermeters as described in IEC 61000-4-15 are used to record flicker, see
Fig. 7.12. The block diagram indicates the input component 1, a quadratic demod-
ulator 2, a band path and weighing filter 3, a variance estimator 4 and a statistic
block 5.
Figure 7.13 shows some typical waveforms in the course of simulation of the
lamp-eye-brain response.
The measuring devices contain a calculating algorithm, using weighing factors
a
i
to apply to cumulative frequency values
P
i%
of the power level spectrum to deter-
mine the short-time flicker strength:
5
1
P
st
=
a
i
·
P
i
(7.7)
Fig. 7.12
Block diagram of a flickermeter
Fig. 7.13
Typical signal waveforms in a flickermeter
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