The Theory,on-site Measurement And Simulation Of Gust Response Factor For Transmission Lines Under Typhoon

The transmission tower-line system will always be subjected to the wind loading during the service.As a kind of large-span and tall structure,it is particularly sensitive to the wind loading.Especially,in the coastal areas of eastern China,where urban power grids are densely distributed,the frequent landing of typhoon caused the collapse of transmission lines on a large scale,and this can be attributed to the lack of understanding of the vibration characteristic of transmission lines under typhoon,especially the underestimate of GRF(Gust Response Factor).In the past,the monsoon model was used to calculate the GRF,but the strong pulsation characteristic of typhoon was ignored.By means of theoretical analysis,on-site measurement and numerical simulation,this paper systematically reveals the evolution law of GRF under typhoon,and analyzes the influence of GRF on the wind-resistance performance of transmission lines.The main research contents and conclusions are as follows:(1)Based on the random vibration theory,the theoretical expression of GRF is obtained.The Mode decomposition method in structural dynamics is used to derive the calculation method of GRF using responses,and the rationality of some assumptions in the theory is verified.Based on actual cases,this paper analyzes the similarities and differences of GRF in five international mainstream transmission line design codes,showing that typhoon is not considered separately in all kinds of codes,but DL / T 5551-2018 is more reasonable.(2)Based on the SHM system,the differences of wind field characteristics between typhoon and monsoon is analyzed,and the law of GRF of transmission lines under monsoon and three typhoons is revealed.The effects of turbulence intensity,wind speed and height on GRF are analyzed,indicating that the critical wind speed and critical turbulence intensity exist in the measured GRF under typhoon and monsoon,respectively.According to the measured results,GRF under typhoon is obviously larger than that of monsoon.Thus,the high turbulence intensity of typhoon must be considered when calculating the GRF in typhoon prone areas.(3)The three-dimensional wind fields of monsoon and typhoon are simulated,respectively,and the wind-induced dynamic analysis is carried out with the monitored transmission line as the research object.The differences between the simulated GRF and the recommended value in DL/T 5551-2018 are compared.The influence mechanism of tower-line coupling effect on GRF is put forward from the structural frequency and mode shapes.Finally,the parameter analysis of wind speed,turbulence intensity and exposure categories is carried out,showing that the three parameters have significant influence on GRF.(4)The influence of typhoon’s high turbulence intensity on the wind-resistance performance of transmission lines is discussed.Based on the uniform defect mode method and birth to death element method,the calculation method of the ultimate wind resistance bearing capacity of transmission lines is determined,and its effectiveness is verified by the full-scale test.On this basis,the wind-resistance performance evaluation framework considering turbulence intensity and span is established,and the influencing factors of wind-resistance performance are analyzed.It is found that the improvement of both can significantly reduce the ultimate wind resistance capacity of transmission lines.Ignoring the high turbulence characteristics of typhoon may bring hidden danger to the service safety of transmission lines.