The New IEEE-404 Test Specification for Joints Highlights the Importance of Connector Selection

On behalf of Hydro-Québec, IREQ undertook the evaluation of heat-shrinkable joints for 25-kV solid dielectric cable using the test schedule described in IEEE Standard 404-1986, a new specification containing higher performance requirements. Unexpectedly, the first batch of test samples failed. dramatically during the early stages of thermal heat and load cycling. Close examination of the joints followed by laboratory experiments, indicated thermal runaway of the connectors as the cause of failure, eventually attributed to faulty connector installation and compression. The experimental techniques and instrumentation used in this investigation are described in detail. The connector installation conditions were modified and the resulting satisfactory performance was demonstrated by testing samples for thermal stability under load-cycling conditions. New jointed-cable test samples were prepared and the splicing system successfully passed all the requirements of IEEE Standard 404-1986. It is now an accepted technique for the Hydro-Québec distribution system. This experience revealed that all aspects of a distribution system must be carefully considered when changes are made in the product performance requirements of any element. In fact all components of the system must be adjusted accordingly in order to provide the overall superior performance demanded by electrical utilities committed to reliable customer service.