Thermal behavior of connectors in joints

One of the main failure causes of MV joints is related to thermal ageing of the joint. The European Standards [1] for MV joints for cables describe heat cycle tests in air and water to evaluate the compatibility of the joint with a specific cable. The connectors used in combination with the joints are tested separately in free air (according to [2]). Investigation on several failures that occurred on qualified joints, mounted with qualified connectors, revealed that the compatibility between the connector and the joint needs also to be tested. Electrical tests have demonstrated that, when a joint and a connector are not compatible, while the cable reaches 110°C during emergency regimes the connectors can reach temperatures in excess of 145°C. Therefore several DGO´s in Belgium started a research program to develop test methods that take into account the thermal behavior of connectors inside the joints. Two test methods are described in this paper.