Zero Clamping - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
18.1.3
Line distance protection REL670 2.2 ANSI
Application manual
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).

Zero clamping

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
U System mean voltage, calculated according to selected mode
I System mean current, calculated according to selected mode
F Frequency
Section 18
Monitoring
817