Abstract It is one of the main causes of conductor overheated fusing failure that the poor contact between conductors and the connecting clamp. In late October 2012, a typical case of that was discovered and dealt with by a power plant in Jilin, China. The project investigates the formation mechanism and development of the failure by laboratory tests combined with simulation method. The investigation indicates that there are two main characteristics of the infrared thermal image when conductors and clamps are poorly contacted—the temperature of the conductor is higher than that of the clamps, and the thermal image of the conductor shows it’s heat-producing like a equidistant helix. The characteristic thermal images provide some practical significance to determine and eliminate the equipment defects timely in inspection routines, thus improving the system reliability.