Electrification Phenomena on Insulating Materials in an Ion Flow Field

Many researchiers have investigated electrical environmental problems under HV transmission lines. Electrification of an object is one of the important factors in the case of dc transmission lines. In this research, electrification of the surface of an insulating material (50 cm square and 5 mm thick PMMA plate) by an ion flow was studied. A rod-plane electrode gap was used to supply the ion flow, and the charge accumulated on the sample surface was measured. From the measurement, the surface potential was evaluated to be about 20 kV maximum for the experimental conditions. Additionally, an unexpected phenomenon was observed. An abnormal decrease of the charge was observed after the removal of the applied potential for the ion supply when the charge on the surface exceeded 70 ¿C/m2. The distribution of charge density was mapped with the use of an electrometer. The distribution was also visualized by sprinkling electrified powder on the surface. The process of this phenomenon is discussed in this-work and the following conclusions are obtained. The phenomenon of decreasing charge is believed to be caused by the fall of ions of opposite polarity and the fall of small neutral particles onto the sample surface. The contour line was observed in the visualized pattern but there was no abrupt variation in the charge density distribution.