Partial discharge in medium voltage extruded cable joints

The main thrust of this work was to interpret the levels of PD in underground distribution extruded cable joints and accessories and use measurement of partial discharges to predict failure. This work also pursues objectives regarding safety of personnel working on underground structures. At first, the concept of a decision threshold (i.e. a PD level above which no work should be allowed) was set as an objective. Earlier papers have reported on a series of accelerated aging tests on brand new joints of the same type and joints removed from service that were designed to find an actual value for this threshold, using a portable PD detector developed by our company. This paper presents selected results on 36 brand new joints of different types. Some of these joints were assembled correctly, but others were set up to fail prematurely, either by making the metallic connector overheat, or by interfacial breakdown.