ABB RET670 Applications Manual page 755

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1MRK504116-UUS C
Application manual
example, via IEC 61850. The possibility to continuously monitor measured values of
active power, reactive power, currents, voltages, frequency, power factor etc. is vital
for efficient production, transmission and distribution of electrical energy. It provides
to the system operator fast and easy overview of the present status of the power system.
Additionally, it can be used during testing and commissioning of protection and control
IEDs in order to verify proper operation and connection of instrument transformers
(CTs and VTs). During normal service by periodic comparison of the measured value
from the IED with other independent meters the proper operation of the IED analog
measurement chain can be verified. Finally, it can be used to verify proper direction
orientation for distance or directional overcurrent protection function.
The available measured values of an IED are depending on the actual
hardware (TRM) and the logic configuration made in PCM600.
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.
The measurement function, CVMMXN, provides the following power system quantities:
P, Q and S: three phase active, reactive and apparent power
PF: power factor
V: phase-to-phase voltage magnitude
I: phase current magnitude
F: power system frequency
Main menu/Measurement/Monitoring/Service values/CVMMXN
The measuring functions CMMXU, VNMMXU and VMMXU provide physical
quantities:
I: phase currents (magnitude and angle) (CMMXU)
V: voltages (phase-to-ground and phase-to-phase voltage, magnitude and angle)
(VMMXU, VNMMXU)
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.
Section 3
IED application
749

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