Fault Phenomenon and Treatment
One phase of 6kV outdoor busbar in a factory is overheated in operation. The temperature is measured by infrared thermometer up to 80 C. The heating place is the lap joint of two busbar, and then the temperature of the other two phases is only 30 C. The bus bar is fitted with an insulated heat shrinkable sleeve with color indication.
Inspection after power outage found that the overlap joint of two bus bars had 5 mm long insulated heat shrinkable sleeve pressed under the overlap joint. In this way, it is impossible to make good contact between the two mother drains, and rainwater will also seep into the contact surface. Because of the increase of contact resistance, the temperature of lap joint increases in operation.
After removing the mother row, it was found that the contact surface had been ablated and pitted. Cut off the excess insulating heat shrinkable sleeve, grind the contact surface with a thin flat file, then coat it with conductive paste (electric compound grease). After the connection is tightened, it is put into operation and no overheating is found. During the acceptance inspection of a newly installed 6kV distribution cabinet in a steel plant, the problem of insulating heat shrinkable sleeve pressing under the contact surface was also found, and the construction unit was promptly re-treated, eliminating the hidden trouble of the accident.
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Insulating heat shrinkable bushing has been widely used in cable and bus because of its high insulation strength, easy construction and simple technology. If the installation and construction are improper, it may cause the junction heat of cable and bus, and arc will start in serious cases, resulting in arc short circuit and other accidents. Great attention should be paid to eliminating potential accidents and ensuring safe production.