Zero Clamping - ABB Relion REC670 Applications Manual

Section 16
Monitoring
All measured values can be supervised with four settable limits that is, low-low limit, low limit,
high limit and high-high limit. A zero clamping reduction is also supported, that is, the
measured value below a settable limit is forced to zero which reduces the impact of noise in
the inputs.
Dead-band supervision can be used to report measured signal value to station level when
change in measured value is above set threshold limit or time integral of all changes since the
last time value updating exceeds the threshold limit. Measure value can also be based on
periodic reporting.
Main menu/Measurement/Monitoring/Service values/CVMMXN
The measurement function, CVMMXN, provides the following power system quantities:
• P, Q and S: three phase active, reactive and apparent power
• PF: power factor
• U: phase-to-phase voltage amplitude
• I: phase current amplitude
• F: power system frequency
,
The measuring functions CMMXU, VMMXU and VNMMXU provide physical quantities:
• I: phase currents (amplitude and angle) (CMMXU)
• U: voltages (phase-to-earth and phase-to-phase voltage, amplitude and angle) (VMMXU,
VNMMXU)
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 amplitude compensation at 5, 30 and 100% of
rated current and at 100% of rated voltage.
The measuring functions CMSQI and VMSQI provide sequence component quantities:
• I: sequence currents (positive, zero, negative sequence, amplitude and angle)
• U: sequence voltages (positive, zero and negative sequence, amplitude and angle).
16.1.3

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
each of the functions. For example, the zero clamping of
VMMXU, zero clamping of I1 is handled by
376
The available measured values of an IED are depending on the actual hardware
(TRM) and the logic configuration made in PCM600.
The power system quantities provided, depends on the actual hardware, (TRM)
and the logic configuration made in PCM600.
ZeroDb for each and every signal separately for
U12 is handled by UL12ZeroDb in
IL1ZeroDb in CMMXU ETC.
1MRK 511 358-UEN A
GUID-8DABC3F5-6615-493C-B839-A5C557A2FAE8 v2
Application manual