Influence of trailing cables on magnetic proximity detection systems
Mining Engineering, 2019, Vol. 71, No. 8, pp. 56-58
Zhou, Chenming; Li, Jingcheng; Damiano, Nicholas; Carr, Jacob; Noll, James
Machine-related injuries are a major safety concern in underground coal mines. Severe injuries and fatalities can occur when a miner is struck, crushed or pinned by mining equipment, such as a continuous mining machine, shuttle car or scoop. Proximity detection systems (PDSs) have been used in mining to reduce these types of injuries and fatalities. All of the PDSs that are currently approved by the U.S. Mine Safety and Health Administration (MSHA) for use in underground coal mines are magnetic-field-based and could be affected by metallic objects such as trailing cables. Researchers from the U.S. National Institute for Occupational Safety and Health (NIOSH) investigated the influence of trailing cables on the performance of PDSs. In particular, the magnetic field coupled from proximity system generators to a de-energized trailing cable was characterized. The results show that significant energy can be coupled from the proximity detection system generators to a trailing cable when there is a closed loop in the cable. The effect on PDS performance from the magnetic field radiated around an energized trailing cable was also quantified for different current amplitudes in the cable. It was shown that the magnetic field caused by the electric current in the trailing cable mainly consists of a 60-Hz signal and its harmonics, which cause little interference to the PDS. The results presented in this paper can help PDS manufacturers to design better systems that are more immune to these effects.
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