Analysis and Treatment of Local Overheating of 500?kV GIS Equipment in a Nuclear Power Plant
During normal operation,a hot spot was found at the A/C phase corrugated pipe support of a 500 kV GIS(SF6 gas insulated fully enclosed composite electrical device)in a nuclear power plant.After on-site infrared temperature measurement,it was found that the temperature of the A phase hot spot was as high as 167℃,the C phase hot spot was about 82.3℃,and the B phase had no hot spot,with a temperature of about 50℃.By analyzing the parameters such as temperature,working current,grounding current,and infrared imaging of the equipment that can reflect the type of equipment overheating,a step-by-step elimination method is used to analyze and determine the cause of equipment overheating.The final cause of overheating is identified as the difference in material and magnetic permeability between the GIS shell and corrugated pipe.The magnetic circuit is diverted through the flange sealing surface bolts,and relatively loose screws have poor magnetic conductivity.Screws with good conductivity are prone to hot spots.After analysis,adding a short copper bar between the upper and lower flanges of the corrugated pipe can eliminate the hot spot problems caused by different materials of the corrugated pipe and varying degrees of screw tightness.After the power outage,the equipment was equipped with a short copper busbar for diversion,and the fixing bolts of the corrugated pipe hot spot flange were replaced.At the same time,the equipment was disassembled and inspected,and the sealing ring of the local hot spot was replaced.After processing,the equipment ran normally,the hotspot disappeared,and the A/B/C three-phase remained at around 45℃.The equipment returned to normal,and the correctness of the fault cause analysis was also verified.
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