Overheat Analysis on the Connection Gap in GIS with the Sections Connected by Bolts

The high-voltage busbar within GIS is usually segmented and assembled with steel bolt on site for ease of installation, transportation and maintenance. Gap may exist between some segmented busbars due to the tolerance, and in which only the steel bolts play the role of current conduction. Therefore when current is larger, the bolt can be melt gradually and fault may be occurred. In response to the short faults in some 220kV GIS, we investi-gated the temperature field distribution between the high-voltage busbars as well as its relationship with the current under different conditions. Furthermore, the coupled multi-physics model considered current, the connection gaps, bolts' material, thread geometries, heat-transfer coefficients and alumina membranes was also built based on the finite element method. The allowable maximal value of the current in three-phase and single-phase busbar in different situations was also calculated. The analysis indicates that the size of the gap has great influence on the temperature. And we find that the temperature will increase at around 10K to 50K with the gap when the bolt material is made of steel. This research will play a guiding role for GIS design and support theoretical base to ensure its long-term safety and reliable operation. © 2017, The editorial office of Transaction of China Electrotechnical Society. All right reserved.