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Electric Power Research Limited

Foroozan Ghassemi

Accurate harmonic measurements on electrical power systems where the main instrument transformers are of the capacitor coupled voltage type (CVT type) is made possible by the provision of one or more current sensors (PQCS, PQCS). CVTs typically have a high voltage capacitor bank (CH) and a low voltage capacitor bank (CL). One or more current sensors (PQCS, PQCS) is/are positioned so as to measure capacitor current and from that the input voltage (Vin) of the CVT can be determined for each frequency.

Capacitor coupled voltage transformer and its input voltage parameter determination

An electric power meter measures the value of an electrical power parameter, e.g., Universal Apparent Power or Universal Power Factor, of an electrical power signal in the time domain by: calculating a first instantaneous power component as the product of an instantaneous voltage signal and an instantaneous current signal of the electrical power signal, carrying out a relative phase shift between the instantaneous voltage signal and the instantaneous current signal; and calculating a second instantaneous power component as the product of the relatively phase-shifted instantaneous voltage and instantaneous current signals. The first and second instantaneous power components are then RMS averaged to determine their respective magnitudes. Both of the calculated magnitudes are then used to determine the value of the electrical power parameter. The method can alternatively be implemented in the frequency domain to produce equivalent measurement values.

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Enfield Island Village, Enfield, United Kingdom

Foroozan Ghassemi