On the accuracy of watt-hour meters in nonsinusoidal environment

This paper deals with the accuracy of induction type watt hour meter operating with harmonic polluted voltage and current waveforms. It starts with the derivation of the registration error resulting from the inherent meter characteristic that exists even for pure sinusoidal voltage and current signals, as well as the error component due to the harmonic content in their time waveforms. A generalized approach is presented allowing for the simultaneous presence of harmonics in both voltage and current. The error is given as a function of three main parameters: the current harmonic distortions HD_i, the voltage harmonic content HD_v and finally the fundamental current. The derived model allows investigating the contribution of each of these parameters to the meter registration error. The effect of both harmonic distortion factors HD_i and HD_v as well as the fundamental current and its displacement factor is illustrated using typical three-dimensional plots. Applying curve fitting techniques, two important approximate relations could be found: the first gives the registration error under pure sinusoidal current and voltage conditions in terms of the peak fundamental current. The resulting equation is insensitive to the current displacement factor. The second relation gives the meter registration error as a function of both distortion factors HD_i and HD_v. The validity of the approximate equation over the entire range of distortion factors is demonstrated