ABB REL650 Applications Manual page 436

Section 14
Monitoring
430
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 VLZeroDB 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:
• 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
The output values are 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 (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.
1MRK 506 334-UUS A
Application manual