ABB ret650, Technical Manual

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Section 14 Monitoring
14.1 Measurements
14.1.1 Functionality
Measurement functions is used for power system measurement, supervision and
reporting to the local HMI, monitoring tool within PCM600 or to station level for
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. There are no interconnections regarding any settings or
parameters, neither between functions nor between signals within each function.
Zero clampings are handled by ZeroDb for each signal separately for each of the
functions. For example, the zero clamping of U12 is handled by ULZeroDb in
VMMXU, zero clamping of I1 is handled by ILZeroDb in CMMXU.
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:
1MRK 504 135-UEN A
Section 14
Monitoring
409
Technical manual