Force safety device for electric substation with flexible buses

The intensity of the short-circuit current sets the design loads for the electric substation structure with flexible buses for voltage up to 115 kV and sometimes for higher voltage. A nonrecoverable force safety device (FSD) incorporated in flexible bus can restrict the transmission of huge unwanted forces to the existing substation portals, while the short-circuit currents intensity increases with time during operation. The FSD may reduce also the cost of new designed portals construction. The proposed device is replaced when tripped, operating similar to a safety fuse of any electrical equipment. The paper deals with theoretical investigation of the FSD efficiency. Two mathematical models (one is to verify another) are built; the first model is based on the finite difference equations and the second one uses ANSYS finite elements program. The finite difference equations are derived by linearization of nonlinear equations of bus motion. Both models include bus conductor, insulators, FSD, portals masses and portals stiffness. A probability approach to the FSD design is considered as well. Results of calculations that show the efficiency of the FSD are presented.