The Development of the Three-Electrode Testing System for the Volume Resistivity of Composite Insulation Materials

The volume resistivity is an important parameter to reflect the electric performances of the insulation materials. In traditional two-electrode testing system for volume resistivity, the influence of the surface current doesn´t be taken into consideration. As a result, higher testing error could be brought about for some insulation materials, especially for those with high resistivity. In order to separate the volume current from the surface current, so as to improve the testing accuracy, a three-electrode testing system has been developed and the corresponding checkouts were performed in this paper. The testing system mainly consisted of five parts that were voltage regulation, electrodes layout, micro-current measurement, data processing and environment controlling, respectively. Especially, a well shielding was designed to avoid the possible interferences. The direct method, namely voltammetry, was used to get the volume resistance of insulation materials. Then, the volume resistivity variations of the composite insulator sample with temperature were measured in the developed platform. The test results show that the developed system has higher accuracy and better reliability. Meantime, the system´s applications and its improvements were discussed.