Study of the influence of test methods on DC pollution flashover voltage of insulator strings and its flashover process

The influence of different test methods on dc pollution flashover voltage of insulator strings is presented in this paper. In addition, the relationship among the flashover voltages obtained by different voltage applied methods is put forward. Subsequently, the pollution flashover phenomenon is investigated using the insight from high-speed photography, and the comprehensive magnitude and orientation of forces on partial arcs is analyzed during the propagation. Thus, a new electrical circuit model consisting of a surface arc of length x₁ and air arc of length x₂ in series with a resistance representing the wet pollution layer supplied by a constant voltage is built. The results obtained from the model indicate that the main reason that makes the exponent b describing the influence of pollution on flashover voltage varying with the configuration and material of insulators is the difference of partial arc fluttering degree for insulators.