Research For Maximum Scale Span Of Isolated Span Of Mined-out Areas In Taiyuan City

The influence on the HV transmission lines above the coal mined-out areas has become increasingly prominent with the growth of UHVDC/UHVAC transmission lines. Shanxi Province is rich for coal energy resources. Because coal mined-out areas are distributed widely, great potential danger and the lower backfilling rate, so it’s a great challenge for the safe operation of different levels transmission lines, which located above the coal mined-out areas or just got through it. Therefore, it’s greatly important for stable and economic operation of the power systems, if we carry out the research for the calculation of maximum scale span in isolated span and develop efficient and comprehensive management plans. In this paper, we carry out our research from three aspects:(1) We analysis the stability mechanism and evaluation index of the coal mined-out areas in Taiyuan city. Based on the basis of previous research, we found that uneven settlement or subsidence is caused by mainly over-harvesting and lower backfilling rate by exploring the mechanism of mined-out areas in Shanxi province. At the same time, the deep-rock ratio and thickness ratio are firstly proposed to describe characteristics of the mining areas. We analyzed the influence on the safe operation of transmission lines, when the two parameters is changed.(2) We discuss the influence of the mined-out area and comprehensive management program on transmission lines. By analyzing the qualitative and the various effects caused by the transmission line and its characteristics, and combining with the mined-out area distribution Shanxi province, we made effective methods for the stable operation of transmission lines in Taiyuan city. We found that the choice of big slab foundation or joint basis, avoiding serious subsidence mining areas, installing tower-line monitoring devices and establishing distributed ledger and so on are effectively to avoid major accidents caused by the mined-out areas in Taiyuan city.(3) Maximum scale span of isolated span model is established and solving equations is derived in the mined-out area. Taking 110kV Caozhuangtou AC transmission line of G3-G4 isolated span in Taiyuan city as an example, we calculated its enormous span, allowing span and scale span respectively when it’s not relaxing and no elevation in overhead transmission lines. The results are 1502m、600.8m.The research could provide the theoretical basis for building HV transmission line above mined-out areas and it has perfect engineering application value.