Finite Element Structural Analysis And Structure Improvement Of 220kV GIS Equipment

GIS equipment, which is known as Gas Insulator Switchgear, is a kind of advanced high voltage switchgear. Since GIS equipment has a lot of merits include low area occupation, high reliability, high environmental adaptability, high security and easy to maintain, it has been widely used in a large number of power stations. But working circumstance of GIS equipment is severe and stress situation is complex. With a large number of GIS equipment put into use and the increasing service time, the device displayed a series of problems such as leakage of SF6, insulation failure and mechanical failure, these problems will severely impact safe and stable running of the equipment. Leakage of SF6 is the most common problem, especially in winter and under severe climate circumstance, this problem not only has bad effect on stable running of GIS equipment, but also will destroy our health and ecological environment. Generally, it is difficult to conduct fully monitor of the equipment through conventional monitor method, so failures cannot be prevented. Through finite element analysis it is convenient to obtain fully learn about stress situation of the equipment, so that the aim of problems prevention, structure improvement and maintenance can be reached.Systematic analysis for static characteristics, multiphysical field coupling and bellows of the equipment has been conducted through finite element method in this thesis. Based on results of structure analysis, structure improvement of some partial structures has been carried out. The main research and work of this thesis are as follows:Overall structure analysis is an effective method to observe stress and deformation situation and to find weak points of the equipment. Analysis of stress and deformation situation of the equipment has been carried out under the effect of internal and external pressure and gravity. Through the overall structure analysis, some weak positions of GIS equipment such as bellows expansion joint, elbow and some other local structures have been found. The refinement of the model and finite element analysis of such local structures have been carried out. The results can help to get a deeply understand of stress and deformation situation of some parts such as bellows, bolts and flanges.The SF6 leakage problem of GIS equipment is more common in winter, thus effect of temperature on stress and deformation of the device should not be ignored. In this paper, the multiphysical coupling analysis method was used to analyze the loss and heat problem of the tubular conductor under the action of the alternating current, the temperature distribution of the busbar has been obtained. The analysis of stress and deformation were conducted under the condition of normal temperature and extreme low temperature respectively. The results initially get effect of temperature on stress and deformation of the equipment.Based on the results of structure analysis, local structural improvement of the GIS device was conducted in this thesis. The structure of bellows was improved: replace flange in square size with flange in circle size; connect flanges with six sets of bolts; and compare stress and deformation situation of bellows expansion after the improvement with that before improvement. Apply improved bellows expansion into model of overall structure and analysis through finite element method, then observe the application effect of bellows expansion after improvement. In addition, the lower end of the supporting rod structure was improved: replace the original fixed structure with the sliding connection structure so that the supporting rod can slide along the Z direction. Bellows expansion cooperate with sliding support bar could adjust deformation and alleviate stress of the device through change constraint condition. It can be seen through the analysis that improvement of constraint condition can help to reduce the stress of local structure in some extend.Meantime, layout adjustment of bellows expansions and support bars was carried out and the overall structural deformation in different layout scheme was analyzed and compared. Numerical analysis results showed that adding of bellows expansion to some large-deformation positions will help to alleviate stress of flanges through compensate large deformation. Adding of support bars to large-deformation positions can prevent appearance of stress on local positions through restrict deformation of the equipment.