Partial discharges in high-voltage insulation of turbogenerators

This paper is aimed at the development of one of the main turbogenerator diagnostic methods - partial discharge galvanic measuring on high-voltage stator winding insulation. For this purpose the stator slot model with inserted stator bars which, in maximal possible measure, respect the real machine electrode configuration were constructed. Artificial defects were created on stator bar samples similar to those which may occur during the technological production process or the machine operation. Samples with a large scale of types of defects like delamination from copper stack, interlayer delamination, stress grading tape on the slot exit, defects on external corona protection in the slot part and samples with undamaged insulation were analyzed in detail. Partial discharge patterns of these defects show considerable dissimilarities. Individual measurements were analyzed and compared in term of phase distribution of measured discharge levels and count of discharge occurrence. Obtained results were confronted with measurements on individual winding phases of turbo generator and the applicability of the model measurements for practical utilization was considered.