New electronic current transformers (ECTs) often adopt a circular array of magnetic sensors for the large current measurement without iron cores. However, the position of this ECT on the measured conductor will directly influence the current measurement accuracy. In this study, we build a 3-D magnetic-field model which is used to analyze the impact of the magnetic-sensor circular array position on current measurement. To meet the accuracy Class 1.0, we estimate the necessary magnetic sensor number and the acceptable position deviation of the ECT. Finally, a new ECT with the circular array of seven magnetic sensors is designed and implemented, which is used to validate the simulation analysis of the ECT position deviation.