Research on using safety pin to prevent collapse of transmission tower in ice calamity

A new kind of protective fitting which is safety pin is put into use in this paper, which can make transmission line dissociate from tower when ice thickness exceed the numerical value that ultimate load related. The approach has achieved the effect of avoiding and decreasing the ice disasters because it efficiently prevents collapse of power transmission tower and disconnection of transmission line. Through the analysis of ultimate load capacity of the 5A-ZM4 transmission tower in the "State Grid Typical Design Transmission and Distribution Projects" the load of controlling tower-line separation is determined. And then the size of safety pin is designed. The ultimate load capacity of safety pin analyzed by nonlinear finite element method through step loading is consistent with the load of controlling tower-line separation. As the loads increase, the safety pin status changes from elasticity to plasticity gradually, and finally the numerical non-convergence occurs. Based on this, the ultimate load capacity of safety pin and load-displacement curve gets. The safety pin meets the engineering requirements in normal use and disconnects necessarily through the analysis of the entire loading process. The order of formation of the microcosmic crack of safety pin and the macroscopic fracture judged through the crack formation criteria verifies the reliability of safety pin. The use of safety pin can achieve the objective of disasters prevention.