The metering of three-phase supplies

The development of electricity supply during recent years has resulted in complexity in the metering of 3-phase supplies and has confronted the meter engineer with the task of achieving accuracy under difficult conditions. It is naturally the large bulk supplies which are the most complex and which demand a high standard of accuracy for commercial reasons. Unfortunately, each additional complexity introduces an additional source of error, and the paper deals with the inaccuracies introduced by auxiliary apparatus and special fitments. It is shown that careful attention must be given to the errors introduced by instrument transformers, interaction and mechanisms.