Use of Cable Surface Temperature to Detect High-Resistance Splices
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Mine power trailing cables are subject to considerable abuse and are quite often damaged severely enough to require a repair splice. Although recently developed splice materials provide a splice that is initially sound both mechanically and electrically, continual flexing of the cable can rapidly cause the splice connectors to loosen, resulting in a significant increase in electrical resistance. Although the added splice resistance does not affect the delivery of power through the cable, it can cause extreme local heating. If heavy current is drawn for several minutes, the splice can catch fire or rupture. Such a failure disrupts production and can be dangerous. Since the added resistance of the splice does not significantly alter the overall cable resistance, it cannot be detected by any measurement of the bulk properties of the cable. A method is suggested for determining splice resistance from a small number of temperature measurements made on the cable jacket while the cable is in use. The advantage of the method is that it requires no knowledge of cable current flow or other electrical parameters but only the cable size and its temperature profile. A theoretical analysis of cable splice heating is presented, relating the results to laboratory experimental data. Data are also presented from several cables in the field, including one which experienced a splice fire shortly after the data were taken. Results are encouraging, suggesting that the method can be developed into a practical periodic check of cable splice characteristics.