Monitoring; Measurements; Functionality - Hitachi Relion 650 Series Technical Manual

1MRK 511 557-UEN Rev. A
Section 12
12.1

Measurements

12.1.1

Functionality

Measurement functions are 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.
All measured values can be supervised with four settable limits, namely 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. Measured 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
• U: phase-to-phase voltage amplitude
• I: phase current amplitude
• F: power system frequency
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 as averaged values over a
period of time (low pass filtered) depending on the selected settings.
The output values can be displayed in the local HMI under Main menu /Tests /Function status /
Monitoring /CVMMXN /Outputs
The measuring functions CMMXU, VNMMXU and VMMXU 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)
It is possible to calibrate the measuring function above to get better than 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.
Technical Manual

Monitoring

The available measured values of an IED are depending on the actual hardware
(TRM) and the logic configuration made in PCM600.
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Section 12
Monitoring
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