电力变压器油箱形变破裂建模及仿真

Modeling and Simulation of Power Transformer Tank Deformation and Rupture

电力变压器内部短路故障过程中油箱鼓包、破裂、甚至爆炸屡有发生,其引发的喷油及起火等次生灾害严重威胁到运行人员人身及周围设备和环境安全。为揭示故障油压骤升与油箱形变和破裂的机理和过程,论文将这一复杂现象视为故障压强和油箱应力两个问题进行建模和求解。首先,建立变压器故障压力模型、油箱瞬态力学模型以及压力场-结构场耦合模型,从能量转换的角度理论描述故障电能与油压和应力之间的对应关系;其次,建立360 MV·A/220 kV变压器3D有限元模型,利用多线性各向同性硬化模型近似油箱箱体的应力应变关系;第三,仿真计算不同故障能量及位置下变压器内部故障压强与油箱应力分布和变化特征。仿真结果表明:故障能量、油压幅值以及油箱应力大小之间存在正相关性;及时切除故障及加固油箱箱壁应力集中区域等措施可以有效提高油箱的耐压和防爆能力,减少或避免喷油及火灾等次生灾害的发生。

Power transformer tank bulging, rupture, even explosion occurs from time to time when suffering internal short-circuit faults. The resulting disasters such as oil spray and fire greatly jeopardize the safety of nearby staffs, apparatus and public environment. In order to reveal the mechanism of abrupt oil pressure increase and successive tank deformation and rupture inside the transformer, this work describes this complex process with two separate stages, i.e. fault pressure and tank stress. The model and corresponding solution of each stage is provided respectively. Firstly, the transformer fault pressure model, tank transient mechanical model and pressure-mechanical field coupling model are introduced. Based on the law of energy conservation, the relationship among the fault energy, oil pressure and stress is interpreted. Secondly, a 3D finite element model is built for a 360 MV· A/220 kV power transformer. In addition, the stress-strain relationship of the tank wall is described by employing a multi-linear isotropic hardening model. Thirdly, the distribution and variation of the internal fault pressure and stress in the transformer tank wall are simulated and analyzed for a variety of fault locations and severities. The simulation results show that some positive correlations exist among the fault energy, oil pressure amplitude and tank stress. It is also found that countermeasures, such as rapid fault clearance and reinforcements for the stress concentration area, are helpful to improve tank＇s capability of overpressure endurance and to reduce the risk of oil spray, fire, tank explosion and other secondary disasters.