ASCO 5010 Remote Display Unit
46
Section 11.
Technical Definitions
No
.
Subject group, Term
Explanation
1
V, I
RMS values of voltage (V) and current (I) parameters. The values are calculated from the measured
discrete sampling of the waveform at the declared resolution of the instrument.
For Current: 256 samples per 50 Hz cycle
For Voltage: depending on the model number; from 256-1024 samples per 50 Hz cycle
2 Voltage
Flickering
A cyclic or quasi-cyclic RMS voltage fluctuation whereby the RMS voltage fluctuates 0.25-4% of
nominal voltage at a frequency in the range of 0.4-25 Hz. This type of disturbance has been
historically defined as causing distress to workers due to flickering lighting, and is described and
defined in the IEC 61000-4-15 standard. ASCO offers parameters the reflect this standard as well as
some variations that ASCO has found to be useful.
3 P
ST
Perceptivity- Short Time: The perception of the flicker over a period of 10 minutes. P
ST
=1 is the
threshold of perceptivity. The P
ST
value is calculated according to the formula dictated by the
EN50160 standard
4 P
LT
Perceptivity- Long Time: The perception of the flicker over a period of 2 hours, calculated from a
sequence of 12 consecutive P
ST
values according to the following formula:
3
12
1
3
12
i
sti
LT
P
P
5 P
SST
An ASCO measurement designed to get quicker results regarding Flicker evaluation. This
measurement reaches a very close approximation of the EN50160 values, but in a fraction of the
time.
The P
SST
is calculated the same as P
ST
but averaged over 2, 10 and 60 seconds. This ASCO defined
value is valuable in that it enables faster assessment of the flicker. ASCO P
SST
converges to a real
value within 3min from a drastic flicker change, or immediately for periodic steady state flicker.
SP
LT
An ASCO measurement designed to get quicker results regarding Flicker evaluation. This
measurement reaches a very close approximation of the EN50160 values, but in a fraction of the
time.
The SP
LT
is calculated the same as P
LT
but averaged over 1 hour. This ASCO defined value is
valuable in that it enables faster assessment of the flicker.
LP
LT
A measurement designed to give better results regarding Flicker evaluation by using a longer
averaging time.
The LP
LT
is calculated the same as P
LT
but averaged over 1 day and 7 days, as per EN50160 parts
4-15. ASCO adds another averaging period of 10 hours to allow a quicker "long term" average.
6
Phasor
A graphic vector rendition of voltage and current magnitude and phase shift between the three
currents and their respective voltages. The phasor diagram is displayed with respect to V
1
(Y) or V
12
(
∆
)
7
PF – Power Factor
The efficiency of power consumption by a load. The ratio between the Apparent Power (Volt-
Ampere) and the Active Power (Watt) described simply as P/S.
A simple representation is offered by calculating the P/S ratio for the first (fundamental) harmonic:
PF
Displacement
=P
H1/
S
H1.
The more accurate PF is defined as the sum of the P/S ratio over all the harmonics: PF
True
= P
Total
/S
Total
= Cos(
θ
).
PF
True
=
2
2
Q
P
P
Where the sums are over N harmonics.
8
E – Energy
Energy is defined as the power in kW consumed over 1 hour. It is measured in kWh.
