Zero Clamping - ABB REB670 Applications Manual

1MRK 505 337-UUS -
14.1.3
Application manual
The CVMMXN function calculates three-phase power quantities by using fundamental
frequency phasors (DFT values) of the measured current respectively 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).

Zero clamping

The measuring functions, CVMMXN, CMMXU, VMMXU and VNMMXU have no
interconnections regarding any setting or parameter.
Zero clampings are also entirely handled by the ZeroDb for each and every signal
separately for each of the functions. For example, the zero clamping of U12 is handled by
UL12ZeroDb in VMMXU, zero clamping of I1 is handled by IL1ZeroDb in CMMXU
ETC.
Example how CVMMXN is operating:
The following outputs can be observed on the local HMI under Monitoring/
Servicevalues/SRV1
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
U System mean voltage, calculated according to selected mode
I System mean current, calculated according to selected mode
F Frequency
Section 14
Monitoring
403