7500A Low Voltage Switchgear Main Bus-bar System Design And Copper Bar Multiphysics Simulation Analysis

Low voltage switchgear is a kind of power transmission and distribution equipment widely used in the field of electric energy distribution and control.After a period of development,low-voltage switchgear has gradually grown from its original bulk and single function to high performance,miniaturization,communication and intelligent.With the development of low-voltage switchgear,the current value carried by the main copper bus-bar in the cabinet is continuously increasing.Under the condition of relatively large current,the cross-section,arrangement and fixed mode of the main copper bus-bar in the switchgear must be strictly designed to satisfy the system cooling and main bus-bar stabilization requirements.In this paper,research object is the 7500 A low-voltage switchgear and multi-physics analysis of the electromagnetic field,thermal flow field and short-circuit electric power of the main copper bus-bar is put forward by simulation analysis.Through the simulation results of the temperature rise and the stress field,the cross-sectional shape of the copper bus-bar,the arrangement and the optimal solution of the main bus-bar system are given.A set of 7500 A low voltage switchgear main bus-bar system is designed.The main research content of this paper are as follows.:(1)FEA was used to simulate the electromagnetic field of the main copper bus-bar and the current density distribution are compared between direct current(DC)and alternating current(AC)conditions with same effective value.When AC is applied,due to induced eddy curren,the current density distribution of the conductor cross-section appears uneven,resulting in the skin effect and proximity effect.For the skin effect,the current distribution and unit length loss of a variety of special shaped copper bus-bar were compared under the same current load conditions.An optimized design scheme for a C-shaped copper bus-bar was given.For the proximity effect,a dual-conductor joint-loaded current was used.By studying the relation between the conductor loss and the arrangement distance between conductors,it was found that the proximity effect weakened as the row spacing increased.(2)According to the analysis of electromagnetic loss value,boundary condition was established and temperature rise simulation of bus-bar was carried,which proved reliable by experiment In the case of natural convection,the distribution of the flow field and the temperature field was analyzed,and the temperature rise dangerous point was found on the copper bar near the circuit breaker.A forced air cooling scheme with convection cooling was given,the cabinet temperature was decreased to 50 K.(3)The dynamic stability check of the main bus-bar copper was carried out.The short-circuit electromotive force variation of the main bus-bar copper was analyzed using the FEA method,and it was found that the B-phase copper bus-bar will receive the most short-circuit electric power.The optimal fixing scheme for the main bus-bar system was designed by the stress strain field results.The short circuit withstand capability test of the main copper bus-bar was designed to verify the accuracy of the simulation analysis.