Section 14 Monitoring14.1 Measurements14.1.1 FunctionalityMeasurement functions is used for power system measurement, supervision andreporting to the local HMI, monitoring tool within PCM600 or to station level forexample, via IEC 61850. The possibility to continuously monitor measured values ofactive power, reactive power, currents, voltages, frequency, power factor etc. is vitalfor efficient production, transmission and distribution of electrical energy. It providesto the system operator fast and easy overview of the present status of the powersystem. Additionally, it can be used during testing and commissioning of protectionand control IEDs in order to verify proper operation and connection of instrumenttransformers (CTs and VTs). During normal service by periodic comparison of themeasured value from the IED with other independent meters the proper operation ofthe IED analog measurement chain can be verified. Finally, it can be used to verifyproper direction orientation for distance or directional overcurrent protectionfunction.The available measured values of an IED are depending on the actualhardware (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 theimpact of noise in the inputs. There are no interconnections regarding any settings orparameters, neither between functions nor between signals within each function.Zero clampings are handled by ZeroDb for each signal separately for each of thefunctions. For example, the zero clamping of U12 is handled by ULZeroDb inVMMXU, zero clamping of I1 is handled by ILZeroDb in CMMXU.Dead-band supervision can be used to report measured signal value to station levelwhen change in measured value is above set threshold limit or time integral of allchanges since the last time value updating exceeds the threshold limit. Measure valuecan also be based on periodic reporting.The measurement function, CVMMXN, provides the following power systemquantities:1MRK 502 048-UEN A Section 14Monitoring471Technical manual
