HT instruments SIRIUS89N - Manual (Page 129)

SIRIUS89N
EN - 127
16.13. MEASURING METHOD: OUTLINES
The instrument is able to measure: voltages, currents, active powers, inductive and
capacitive reactive powers, apparent powers, inductive and capacitive power factors,
analogic or impulse parameters. All these parameters are analyzed in a digital way: for
each phase (voltage and current), 6 x 128 samples are acquired on a module of 16 x
20ms, repeated for the three phases.
16.13.1. Integration
periods
The storage of all the data would require a huge memory capacity.
Therefore we’ve tried to find out a storage method which permits to compress the
information to be memorised, though providing significant data.
The chosen method is the integration one: after a certain period called “integration period”,
which can be set from 5 seconds to 60 minutes (3600sec), the instrument extracts from
the sampled values the following values:
• Minimum value of the parameter during the integration period (harmonics excluded)
• Medium value of the parameter (intended as arithmetic average of all the values
registered during the integration period)
• Maximum value of the parameter during the integration period (harmonics excluded)
Only this information (repeated for each parameter to be memorised) are saved in the
memory along with starting time and date of the integration period.
Once these data are memorised, the instrument restarts to take measurements for a new
period.
16.13.2. Power
factor calculations
According to the standards in force, the medium power factor can’t be calculated as
average of the instantaneous power factors. It must be obtained from the medium values
of active and reactive power.
Each single medium power factor (of phase or total) is therefore calculated, at the end of
each integration period, on the medium value of the corresponding powers independently
on the fact that they must be registered or not.
Besides, for a better analysis of the type of load present on the line and in order to have
terms of comparison when studying the invoicing of the low cos
ϕ, the values of inductive
and capacitive cos
ϕ are treated as independent parameters.