Power measurement in the presence of harmonic distortion

Due to the rapid progress in power electronics, more and more energy is transmitted at nonsinusoidal voltage and current. However, the instrumentation controlling the flow of energy in such situations remains almost the same as is used for sinusoidal waveforms. The necessity of understanding these phenomena stems from the fact that they determine the efficiency of the power transmission and the possibility of power factor improvement. They also affect the energy accounts. It is possible to digitize the phase voltage synchronously with the current every T seconds over the cycle and the power can be digitally calculated. This approach will yield the real power at all the harmonic frequencies present. It is found from results of various practical cases that the harmonic content of the load waveform affects power measurement significantly. Furthermore, it is shown that, with sample data techniques, true power or energy consumed by the distribution system can be determined