Error analyses of a 3-phase electricity meter with class-0.5 accuracy

A design of a 3-phase TOU electricity meter with IEC687 class 0.5 accuracy is proposed. The emphasis is upon its error analyses. Current transformers and voltage dividers are chosen to be the current and voltage transducers respectively. Two T1 ADS8345 16-bit A/D converters are used to digitize 3-phase current and 3-phase voltage signals independently. The Dallas DS89C450 microcontroller processes data with 16-bit fix-pointed calculation. Experiment results show that the accuracy of the meter lies within ranges specified in the IEC687 standard. Error Analyses are compared with the measured results, and show that the main cause of error is variation of the phase shift of the CT.