Underground Medium-Voltage Cable Rejuvenation—Part III: Influence of Operating and Emergency Conditions

The present study, the last of three parts, deals with the testing of three solutions for the blocking of cable-ends of silicone injected cables on an underground experimental line at up to maximum operating conditions. Another objective is to verify in the laboratory the impact of emergency conditions on silicone-injected cables. The experimental line is composed of 16 triplexed XLPE cable sections, rated 28-kV, having 750-kcm aluminum conductors; the line comprises also 42 splices. Only two phases of each cable section were silicone-injected by a service provider. It was found that the solution to dam cable-ends after silicone injection performs successfully and, also, that the silicone diffuses rapidly in the cable´s extruded layers. It was further revealed that, with freshly injected cables problems arise due to high conductor temperature above 100^°C, but it becomes harmless a few months after injection.