The current sensor of the voltage-current sensor system proposed by us is two air-core sensing coils connected in series to each other with an opposite polarity. By doing so, it can measure the harmonics and power factor while removing the influence from power lines of other phases. When the sensors are surrounded by an iron case, emf may be influenced. However, it has been confirmed that a large change is not observed with regard to measurement of harmonics, and the proposed sensors can be used without problem. Therefore it was found out that the proposed sensor is able to perform power measurements in a state of being incorporated in the pole switch.