The pictures below show a geometric type stress relief used on a 15kv cable. The cable was an XLP, Al-750MCM, 15kv, 133%. The installation was about 15 years old and the problem was discovered as a result of a routine transformer test. The center phase cable had heated significantly enough to melt and distort the cable insulation. What is not seen in the pictures is that the cable insulation had started to split vertically on the side toward the transformer from the top of the termination down to the stress relief ball. The connection was not loose and no visible sign of moisture was noted leaking into the cabinet. The cause of the problem was not obvious and in my opinion was related to the preparation of the cable during construction. Possibly a knife score left in the stripped out area or insufficient cleaning. It was determined that the cable was under sized for the transformer full load rating. This was replaced with a Cu-750MCM, 133%, EPR insulation cable.