• I: phase currents (magnitude and angle) (CMMXU)
• V: voltages (phase-to-
ground and phase-to-phase voltage, magnitude and angle)
(VMMXU, VNMMXU)
The CVMMXN function calculates three-phase power quantities by using fundamental
frequency phasors (DFT values) of the measured current and voltage signals. The
measured power quantities are available either, as instantaneously calculated quantities
or, averaged values over a period of time (low pass filtered) depending on the selected
settings.
It is possible to calibrate the measuring function above to get better then class 0.5
presentation. This is accomplished by angle and magnitude compensation at 5, 30 and
100% of rated current and at 100% of rated voltage.
The power system quantities provided, depends on the actual hardware,
(TRM) and the logic configuration made in PCM600.
The measuring functions CMSQI and VMSQI provide sequence component quantities:
• I: sequence currents (positive, zero, negative sequence, magnitude and angle)
• V: sequence voltages (positive, zero and negative sequence, magnitude and angle).
18.1.3 Zero clamping
GUID-8DABC3F5-6615-493C-B839-A5C557A2FAE8 v4
Measuring functions CVMMXN, CMMXU, VMMXU and VNMMXU have no
interconnections regarding any settings or parameters.
Zero clampings are also handled entirely by ZeroDb separately for each function's
every output signal. For example, zero clamping of U12 is handled by UL12ZeroDb in
VMMXU, zero clamping of I1 is handled by IL1ZeroDb in CMMXU, and so on.
Example of CVMMXN operation
Outputs seen on the local HMI under Main menu/Measurements/Monitoring/
Servicevalues(P_Q)/CVMMXN(P_Q):
S Apparent three-phase power
P Active three-phase power
Q Reactive three-phase power
PF Power factor
ILAG I lagging U
ILEAD I leading U
Table continues on next page
1MRK 504 163-UUS A Section 18
Monitoring
Transformer protection RET670 2.2 ANSI 865
Application manual
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