Partial discharges in internal voids: dependence on defect position with respect to electrodes

A study on the behaviour of partial discharge (PD) activity occurring in insulation cavities as a function of their position with respect to electrodes is presented in this paper. PD measurements were carried out on different specimens, with different defect positions and geometries. Test results permit to develop an algorithm based on fuzzy logic, which is able to locate the defect position starting from the phase-resolved PD pattern, on the basis of its dissymmetry on the two half-cycles of the supply voltage. The algorithm works correctly for low over-voltage ratios, for symmetric electrode geometry (i.e. for uniform electric fields) and when the distance between electrodes is relatively large.