An Evaluation of High-Voltage Cable-Coupler Performance for Underground Mine Power Systems

High-voltage cable couplers are convenient and widely used accessories in modern coal-mine power distribution systems for aiding in the extension and retraction of power-feeder cables throughout a mine. Coupler design has tried to keep pace with the industry's desire to move to higher distribution levels, but the increase in recorded failures of 15 kV-class couplers, which serve the distribution levels of 12.47 kV and above, have inhibited this transition. The problems associated with high-voltage cable couplers are analyzed. Manufacturing, testing, and mounting practices are reviewed. A discussion of a coupler's operating environment is also included. On the basis of the aforementioned conditions, a testing standard is developed and various coupler designs are subjected to its requirements. An analysis of the test results is provided. Although new couplers can satisfy the performance requirements of the cables to which they are mounted, partial discharge appears to be the failure mechanism of concern. The effects of partial discharge are magnified where voids, either in the insulation, cable termination, or potting compound, occur. In this regard, it is shown that the quality of installation of a coupler onto cable is quite critical. By slightly altering the mounting procedure, satisfactory partial-discharge readings are produced on a test coupler.