基于三维热力场耦合分析的换流变压器网侧干式套管拉杆连接结构力学计算及优化设计

Mechanical Calculation and Optimization Design of Pull-Rod Connection System of Gride-Side RIP Bushing of UHVDC Converter Transformer Based on 3D Thermal-Mechanical Coupling Analysis

换流变压器网侧套管在换流站系统运行中承担着关键作用,但在实际运行中其拉杆连接结构多次发生如拉杆断裂、拉杆与载流端子松脱等故障。本研究针对某出现故障的550 kV换流变网侧干式套管,采用三维电磁-热-流场耦合分析方法及热力场耦合分析方法,建立了套管及拉杆连接结构精细化模型,考虑了热传导、热对流、热辐射等条件,计算了网侧套管温度场及应力应变场分布。结果表明:换流变网侧干式套管的拉杆连接系统附近温度较高,拉杆表面大部分区域受到较大应力作用,拉杆与载流端子插接处应力极大,在工况反复热胀冷缩及换流变压器振动等因素的共同作用下可能导致拉杆与载流端子插接处脱开,电气连接失效。同时提出了采用导杆式插接结构替换拉杆连接系统的优化设计方案,通过仿真分析验证了导杆式套管温度分布及应力应变分布满足安全稳定运行的热裕度和机械裕度,为后续生产试验提供依据。

Net-side bushing of UHVDC converter transformer plays a key role in the operation of converter station system.However,in actual operation,pull rod connection system often failure,such as pull rod and current carrying terminal are separated.In this study,a refined model of bushing and the connection structure of pull rod is established for a faulty 550 kV net-side bushing of UHVDC converter transformer.Considering the conditions of heat conduction,heat convection and heat radiation,through the 3D electromagnetic-thermal-fluid coupling analysis method and thermal-mechanical coupling analysis method,the temperature field and stress-strain field of the net-side bushing are simulated.The results show that:the temperature near the pull rod connection system of net-side bushing is higher,most areas of the pull rod are subjected to higher stress,and the stress at the connection between the pull rod and the current carrying terminal is extremely high,Under the combined action of repeated high and low temperature cycles and converter transformer vibration under actual working conditions,it may lead to the disconnection between the pull rod and the current carrying terminal and the failure of electrical connection.At the same time,the optimization design of replacing the pull rod connection system with the current-carrying conductor structure is proposed.The simulation analysis verifies that the temperature distribution and stress-strain distribution of the current-carrying conductor type bushing meet the thermal margin and mechanical margin of safe and stable operation,which provides the basis for the subsequent production test.