Research On Lightning Protection And Grounding System In Qinghai-Tibet Railway Ge-La Segment

Qinghai-Tibet Railway passes through Qinghai-Tibet Plateau. The length of this railway is about 1100km, the average height above sea level of 84% length locates above 4500m and 50% of railway passing through the perennial frozen sediment soil area of Qinghai-Tibetan Plateau. This zone has high frequency thunderstorm, and the soil resistivity reaches to 3000Ω·m. The frozen soil and altiplano are the main problems during the construct of Qinghai-Tibet Railway. Because of the special geologic and climate condition, the design and implement of grounding system and lightning protection in Qinghai-Tibet Railway is difficult to that in the other zones. Today, the systemic research of grounding system and lightning protection in Qinghai-Tibet Railway is blank in the world. To keep the Qinghai-Tibet Railway safe, it is importance and necessary to start this research.To summarize and analyze the thunderstorm condition along the Qinghai-Tibet Railway, the form, characteristic, activity rules and lightning parameters of plateaus thunderstorm are introduced. Some protection principles to transmit electricity systems in this zone are recommended. To keep the lightning protection level of 35kV transmission line along the railway meets the design demands and reduces the construct difficulty, the methods of fix arrester is recommended. First, the simulative module of 35kV transmission line is set up. The influence of different fix condition of arresters in tower on lightning protection level is analyzed. Then the arrester fix method is recommended.To reduce the grounding resistance of substation, the geologic condition of Ge-La segment is introduced. The design principles of substation grounding grid are recommended. To farther reduce the grounding grid resistance, the reducing-resistance module is analyzed. The simulative exam is applied in Sichuan Balang Mountain to prove the grounding result. The results show that the module has better than the metal grounding rod.Obtain exact soil structure parameters is the basic of the grounding system design. The Laplace equation is applied to calculate the potential distributing of point current source in multi-layer horizontal soils, and then the relationship between the apparent soil resistivity and measurement pole span (ρ-αcurve) is obtained. According to the actualρ-αcurves, which are measured on the spot in substations of Wang-Chu segment in Qinghai-Tibet Railway. The soil structure model of this area is obtained. To analyze the influence of soil structure on grounding resistance, the horizontal two-layer soil structure is applied. The influence of grounding area, top-layer soil height change on resistance is discussed. The results show that the top-layer soil height and reflect factor have better influence on grounding resistance.