Study of the effect of harmonics on measurments of the energy meters

An investigation of the effect of voltage and current harmonics on the accuracy of readings of energy meters was carried out. Harmonic distortion is one of the power quality problems, which typically arises from the consumer´s electrical equipment. Such harmonics produced by discontinuous conducting devices and non-linear loads create recognized problems for most power distribution systems. These problems can lead to over heating and power losses of power system distribution components. Such conditions involved differences in voltage and current magnitudes as well as differences in the voltage and current total harmonic distortion levels. This study presents comparison between the electromechanical energy meters and the electronic digital energy meters. The study also includes the accuracy of readings when the meters are subjected to the same non-linear similar conditions. The harmonics were measured using VIP system III illustrating the THD of voltage and current when power factor compensating capacitors were used or not. It was found that the accuracy and the sensitivity as well as the precision of digital electronic meters are higher than that of the electromechanical one. When using both meters to read the energy consumed by the loads, it was noticed that there is a difference between readings of the two compared types as the digital electronic meter has a difference of (± 0.5% to 1%) which is a considerable amount of energy for large consumers. An economical assessment was made and showed that the digital meter is saving about L.E 1.8 to 3.6 million per annum for the distribution company. It is recommended to distribution companies to use digital meters instead of electromechanical ones especially for large and medium consumers.