Mega MEg40+, Manual

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Měřící Energetické Aparáty
41
disPlay and EvalUation Using a PErsonal coMPUtEr
The data obtained during operation of the monitor and stored in its memory for further
use are transmitted into a personal computer. The simplest operations with the transmitted
data include statements. For each of the detected events, place (phase), type, size, time
duration and time of occurrence is specified. Another example can be a statement of
quarter-hour maximum phase currents with the times of occurrence.
The displayed time courses provide wide application. They include a display of
characteristic data obtained gradually in the follow-up recording intervals. For voltages
and currents in the individual phases, such data include total or average RMS values,
minimum RMS value and maximum RMS value. For the active, reactive and apparent
power, they are average, minimum and maximum values, similarly for the coefficient of
performance (true power factor). It is also useful to display time curves of the average,
minimum and maximum values of the total harmonic distortion and selected harmonics.
Statistical evaluation with subsequent displaying of results in the form of histograms and
cumulative diagrams is also considered. This applies to the above mentioned quantities
but without their time curves. Simple numerical expression is often sufficient, e.g. what
percentage of supply voltages detected in ten minute intervals is outside ± 10 % of the
rated value.
The personal computer allows additional processing of displayed data. It is also possible
to make additional time aggregation. The period T
v
is determined as an M -multiple of
the recording interval, i.e. T
v
= M T
z
. From the data collected for the recording intervals
during the period T
v
, the corresponding data are evaluated for the period T
v
. Then if
U
zc
( m ) are total RMS voltage values belonging in the recording interval with the serial
numbers m = 1, 2, … M during the time T
v
, the voltage during the time T
v
has the total
RMS value
(17)
minimum and maximum value
(18)
The same procedure is used for currents. The average active power in the time T
v
is
(19)
and the minimum and maximum active power is also computed.
( )
m U
M
U
M
m
zc vc
∑
=
=
1
2
1
min min
min
z
m
v
U U =
max max
max
z
m
v
U U =
( )
∑
=
=
M
m
z v
m P
M
P
1
1