A study of polyphase watthour meter accuracy comparing single phase series to polyphase calibration

This paper examines the accuracy of polyphase watthour meters derived from two methods of calibration. The standard single phase series method is compared to the three phase method of calibrating polyphase transformer rated and self-contained induction type watthour meters. A total of seventy two meters from four different manufactures are tested. Sixty of these meters are tested at full load, full load with 0.5 lagging power factor and light load for each of the calibration methods. Twelve meters are further tested over a greater range of loading conditions. Also, the effect of rotating the phase of the input conductors on the meter´s accuracy is examined