Juraszek Janusz
Faculty of Materials, Civil and Environmental Engineering, University of Bielsko-Biala, 43-309 Bielsko-Biala, Poland.
Materials (Basel). 2020 Mar 27;13(7):1559. doi: 10.3390/ma13071559.
The reliability and safety of power transmission depends first and foremost on the state of the power grid, and mainly on the state of the high-voltage power line towers. The steel structures of existing power line supports (towers) have been in use for many years. Their in-service time, the variability in structural, thermal and environmental loads, the state of foundations (displacement and degradation), the corrosion of supporting structures and lack of technical documentation are essential factors that have an impact on the operating safety of the towers. The tower state assessment used to date, consisting of finding the deviation in the supporting structure apex, is insufficient because it omits the other necessary condition, the stress criterion, which is not to exceed allowable stress values. Moreover, in difficult terrain conditions the measurement of the tower deviation is very troublesome, and for this reason it is often not performed. This paper presents a stress-and-strain analysis of the legs of 110 kV power line truss towers with a height of 32 m. They have been in use for over 70 years and are located in especially difficult geotechnical conditions-one of them is in a gravel mine on an island surrounded by water and the other stands on a steep, wet slope. Purpose-designed fiber Bragg grating (FBG) sensors were proposed for strain measurements. Real values of stresses arising in the tower legs were observed and determined over a period of one year. Validation was also carried out based on geodetic measurements of the tower apex deviation, and a residual magnetic field (RMF) analysis was performed to assess the occurrence of cracks and stress concentration zones.
输电的可靠性和安全性首先取决于电网的状态，主要取决于高压输电线路杆塔的状态。现有输电线路支架（杆塔）的钢结构已经使用多年。它们的服役时间、结构、热和环境荷载的变化性、基础状态（位移和劣化）、支撑结构的腐蚀以及技术文件的缺失都是影响杆塔运行安全的重要因素。迄今为止所采用的杆塔状态评估，包括测量支撑结构顶点的偏差，是不够的，因为它忽略了另一个必要条件，即应力准则，也就是应力不得超过允许应力值。此外，在困难的地形条件下，测量杆塔偏差非常麻烦，因此往往不进行测量。本文对高度为32米的110 kV输电线路桁架式杆塔的腿部进行了应力应变分析。这些杆塔已经使用了70多年，位于特别困难的岩土工程条件下——其中一个位于被水环绕的岛屿上的砾石矿中，另一个矗立在陡峭、潮湿的斜坡上。提出了专门设计的光纤布拉格光栅（FBG）传感器用于应变测量。在一年的时间里观测并确定了杆塔腿部产生的实际应力值。还基于杆塔顶点偏差的大地测量进行了验证，并进行了残余磁场（RMF）分析，以评估裂纹和应力集中区域的出现情况。
