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
Protected
Object
P Q
ANSI05000373_2_en.vsd
52
IED
ANSI05000373 V2 EN
Figure 208: 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.
12.1.8.3 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 outputs
and IEC 61850. This is achieved by magnitude and angle compensation at 5, 30 and 100%
Section 12 1MRK 511 287-UUS A
Monitoring
448
Technical manual
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