Phase Current Measurement Cmmxu - ABB REG650 Technical Manual

Section 14
Monitoring
14.1.8.3
420
Directionality
CTStartPoint defines if the CTs grounding point is located towards or from the
protected object under observation. If everything is properly set power is always
measured towards protection object.
Busbar
52
P Q
Protected
Object
ANSI05000373 V2 EN
Figure 198: Internal IED directionality convention for P & Q measurements
Practically, it means that active and reactive power will have positive values when they
flow from the busbar towards the protected object and they will have negative values
when they flow from the protected object towards the busbar.
In some application, for example, when power is measured on the secondary side of the
power transformer it might be desirable, from the end client point of view, to have
actually opposite directional convention for active and reactive power measurements.
This can be easily achieved by setting parameter PowAngComp to value of 180.0
degrees. With such setting the active and reactive power will have positive values
when they flow from the protected object towards the busbar.
Frequency
Frequency is actually not calculated within measurement block. It is simply obtained
from the pre-processing block and then just given out from the measurement block as
an output.

Phase current measurement CMMXU

The Phase current measurement (CMMXU) function must be connected to three-phase
current input in the configuration tool to be operable. Currents handled in the function
can be calibrated to get better then class 0.5 measuring accuracy for internal use, on the
IED
ANSI05000373_2_en.vsd
1MRK 502 043-UUS B
Technical Manual