Faults Evaluation of MV Underground Cable Joints

During the summer periods of the last few years there have been unexpected increased numbers of failures of underground cable joints of the medium voltage (MV) network both of e-distribuzione and of other Italian electrical distributors. As a result of this, the University of Roma “La Sapienza” and e-distribuzione started a cooperation with the aim to investigate on causes of such failures and for finding the most appropriate countermeasures in terms of improvement of technologies, operative procedures and operation. This paper reports the main results of a temperature measurement campaign on such MV underground cable joints and an experimental inspection on both failed and not failed cable joints. In this contribution, a discharge mechanism and the ongoing adopted mitigation actions are also presented. The gained information will be useful in re-designing innovative more robust and resilient joints for medium voltage underground cables.