Abstract:

Because of the pull effect of flexible bus， strong interaction exists in substation equipment interconnected by flexible bus during severe earthquake. The substation equipment was simplified as a single degree of freedom system with lateral stiffness， and the flexible bus was simplified as a spring with variable stiffness. The effective stiffness of the spring was obtained according to the suspension theory. Then a kinetic model of single span structure was built for the electrical coupling equipment interconnected by flexible bus， and solved by using the Newmark-β method combined with Newton iteration. Through the analysis of the structural features and equipment parameters， it shows that the tension stiffness of flexible bus has a nonlinear growth with horizontal span， and the characteristic frequency of coupling system is influenced by the natural frequency of standalong equipment， the quality ratio and the effective stiffness of flexible bus. It is found that there is a critical rise-span ratio under seismic action. When the rise-span ratio of flexible bus is smaller than the critical ratio， large tension generates in the bus， and the seismic response of equipment is greatly influenced by equipment frequency. So during the seismic design of substation equipment interconnected by flexible bus， the influence of critical rise-span ratio must be considered.

Key words: substation coupling equipment, flexible bus, seismic action, effective stiffness, rise-span ratio, numerical simulation