Numerical Simulation and Stability Analysis of Internal Explosion of Transformer Net Side Bushing by SPH Method

The net side bushing is an important part of the transformer. During operation, the cooling oil inside the bushing will explode due to insulation breakdown, which will cause great potential safety hazard to the transformer. Therefore, it is of great significance to carry out quantitative evaluation of the net side bushing explosion accident. In this paper, a two-dimensional transformer bushing model was established by nonlinear finite element software ANSYS/LS-DYNA with smooth particle hydrodynamics (SPH) method. The dynamic response of transformer bushing under internal explosion was simulated. And the influence of different parameters on the failure characteristics of bushing was analyzed. The instability time of bushing was evaluated by the stability judgment method based on the curves of radial particle velocity. The results show that under the action of internal explosion, the middle part of the bushing is first damaged under the combined action of tension and compression of the inner and outer surfaces, and the overall damage of the bushing shows a convex trend during the propagation of the shock wave. The high explosion equivalent, the existence of cooling oil and initial crack defects have a greater influence on the stability of bushing. The decrease of explosion equivalent can change the failure mode of bushing from bidirectional shear failure to tensile failure, and the influence on overall stability is also reduced. When the explosion source is located on the outer wall of the conductive rod, the shock wave radiated by the cooling oil not only makes the bushing instability time advance, but also causes the outer wall expansion damage range to become wider. The stress concentration and the decrease of effective wall thickness make the shear failure instability of bushing with initial crack defects develop rapidly.