HT instruments VEGA78 - Manual (Page 123)

VEGA78
EN - 121
10.5. MEASURING METHOD: OUTLINES
The meter is capable of measuring: voltages, currents, active powers, inductive and
capacitive reactive powers, apparent powers, inductive and capacitive power factors,
energies, analogical or pulse parameters. All these parameters are analysed in a digital
way for each phase (voltage and current) and calculated based on formulas of the
previous sections.
10.5.1. Integration period
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 saved providing
significant data.
The selected method is the integration one: after a certain period called “integration
period”, which can be set from 1 seconds to 60 minutes, the meter extracts from the
sampled values the following values:
 MINIMUM value of the parameter during the integration period (harmonics excluded).
 AVERAGE value of the parameter (intended as arithmetic average of all the values
recorded during the integration period).
 MAXIMUM value of the parameter during the integration period (harmonics excluded).
Only this information (repeated for each parameter to be stored) are saved in the memory
along with starting time and date of the integration period.
Once these data are stored, the instrument restarts to take measurements for a new
period.
10.5.2. Power factor calculations
According to the standards in force, the medium power factor cannot 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
of 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 get
reference terms in the invoicing analysis of the low cos
, the values of inductive and
capacitive cos
 are treated as independent parameters.