Compression Connectors for Stranded Aluminum Power Conductors

Twelve different commercial compression connectors for 240 mm2 stranded aluminum cable conductors have been examined in order to identify and clarify the correlations between the quality of a connector and its design characteristics, assembly procedures, and other relevant parameters. The quality of the connectors is assessed with basis in resistance measurements during shortcircuit tests and thermal cycling as specified by the IEC 61238-1 standard. Visual inspections of cross-sectioned connections, hardness measurements, and other examinations revealed that large mechanical deformations in connector-conductor interfaces significantly improve the quality. Connecting soft (annealed) conductors is considerably more difficult than hard-drawn conductors, but excellent results can be obtained if the work hardening during compression increases the conductor hardness to a level approaching that of hard conductors. The sequence in which the compression indents is made can be decisive for the quality of a connector. Unless the connector barrel or sleeve contains excessive amounts of contacting compound, it is advantageous to set the first indents at the ends of the barrel and the last ones in the middle.