16 M4M 20 NETWORK ANALYZER USER MANUAL
4.Measurement method
Import energy registers increments when the power is positive and export energy registers increments
when power is negative.
All import and export registers are positive (or zero) and will either increment or stand still. Net energy
registers contains the import minus the export register for corresponding registers and can be positive
or negative.
The ABB M4Ms use the vector registration method for computation of energy.
4.1.Vector registration method
In the vector registration method the instantaneous energy consumption of the measuring elements (the
three phases in 3-phase 4-wire metering) is summed up to the total register. If the sum is positive the
import register is incremented and if the sum is negative the export register is incremented.
Say for example that the power in the three phases are L1: +1 kW, L2: -1 kW and L3: +1 kW. The total power
will then be 1 – 1 + 1= 1 kW and the total import register will increase at a rate of 1 kWh each hour and the
total export register will stand still.
If the power in the three phases instead are L1: +1 kW, L2: -1 kW and L3: -1 kW the total power will be 1 – 1
-1= -1 kW and the total export register will increase with the rate of 1 kWh each hour and the total import
register will stand still.
Note that if a 3-phase load with neutral have connections between the phases that have a power factor
smaller than 0.5, that is constitute a mainly reactive load, the power in single phases can be negative even
if the 3-phase load is consuming energy. The total power and energy will however always be positive for a
3-phase load that is consuming energy.
Note also that the sum of the per phase registers will be bigger than the total register if the power in the
phases contains a mix of both positive and negative power. In applications where the load is a 3-phase
load the total register should always be used for billing.
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