Crossing construction is one of the processes with the greatest safety risks during the erection of transmission lines. Guide ropes, traction ropes and ground conductors of various specifications are towed above the crossed object. In order to ensure the safety of the crossed object, a frame body higher than the crossed object is generally erected on both sides of the crossed object to serve as a temporary support facility for construction and to bear the impact of wires that may occur under fault conditions. Accidents caused by insufficient strength of the crossing frame during the pay-out process also occur from time to time. With the development of science and technology, on the one hand, the voltage level of overhead transmission lines has increased, the height of towers has increased, the cross-section of conductors has increased, and the number of sub-conductors has increased, resulting in an increase in the impact force under the failure state of laying out construction. On the other hand, the number of important crossings such as high-speed railways, highways and live lines is increasing. If crossing by conventional methods, there are major hidden dangers. It is necessary to improve the methods and devices for crossing over construction to effectively improve the safety and reliability of major crossings such as high-speed railways and high-speed. At the same time, improve the level of mechanized construction to ensure construction safety. After years of exploration and improvement, this project has developed a series of high-strength lattice spanning frames for transmission lines, and conducted comprehensive impact tests and analysis, filling gaps in domestic and foreign industries and forming three major technological innovation points: 1) Invented the technology of large-scale lattice-type crossing frame, proposed the idea of using a large number of existing tower groups and holding poles in the construction unit to form the crossing frame, invented a six-way connection piece, and developed a large-scale lattice-type crossing frame that can be flexibly combined, improving the impact resistance of the crossing frame, improving the utilization rate of the equipment, and realizing the mechanized and rapid construction of the crossing frame. 2) Invented the hard-capped lattice-type crossing frame technology and proposed the idea of replacing the current ldquo; soft closed netrdquo; protection method based on hard protection. The ldquo; dual-arm hydraulic propulsion type rdquo; hard capping system composed of a lattice-type frame body, a beam, a protective beam and a hydraulic propulsion device, optimizes the structural force of the capping of the crossing frame and improves the safety and stability of the sealing net at the top of the crossing frame. 3) The impact laws of conductor running and breaking accidents on the spanning frame are revealed. Based on verifying the impact of the laying off fault state on the spanning frame and the ability of the spanning frame to withstand fault impact, an impact test plan is formulated and simulated fault conditions are carried out. Impact test research reveals the impact laws of conductor running and breaking accidents on the spanning frame, and provides technical support for parameter verification, engineering application and achievement promotion. This project has been authorized 2 invention patents, 4 utility model patents, published 6 papers, and completed 2 industry standard reports and reviews. This project has been appraised by the scientific and technological achievements of China Society of Electrical Engineering. It is believed that the research results of the project have improved the safety level of objects being crossed under accident conditions. The results have significant field application value and good application prospects. They have generally reached the international and domestic advanced levels, among which they are in the forefront of hard capping of spanning frames and spanning frame impact testing. The project's research results have been mature and applied 18 times in 8 line projects including the Beijing-Shanghai high-speed railway, including 14.3982 million yuan in direct economic benefits in the past three years. The application results show that the crossing frame has high mechanization, high construction efficiency, low operation risks, strong impact resistance, stronger protection against objects being crossed, and obvious economic and social benefits. This achievement was recognized and promoted on a special basis by the State Grid Corporation of China, and was included as a typical equipment for mechanized construction technology. This project won the first prize in Science and Technology Progress Award of State Grid Shanghai City Electric Power Company in 2017. This project has developed mature and been promoted and applied in the construction of Shanghai, where the road network is developed. There are many application methods. In particular, the hard-capped crossing frame forms a closed protection for the objects being crossed, which can cope with harsh conditions and create good conditions for the uninterrupted operation of protected roads and railways under the crossing frame and the uninterrupted construction of high-voltage lines above the crossing frame, and has broad prospects for promotion and application.