Structural modelling of corrugated tank of hermetically sealed transformers under dynamic loading

Hermetically sealed transformers are essential for applications that require the exclusion of moisture, oxygen and other contaminants from the transformer tank, thereby protecting the insulating fluid. This increases the lifespan and reliability of the transformer and reduces maintenance costs. The objective of this paper is to provide an analytical approach to modelling and predicting the structural behaviour of hermetically sealed transformers under dynamic thermal loading, with a focus on the sizing of the corrugated tank fins. The study involves determining the change in oil volume due to thermal expansion from winding power losses, resulting in an increase in pressure within the tank. This pressure change primarily causes deformation of the tank fins, requiring evaluation of mechanical stresses and deformations to ensure structural integrity. A simplified geometric model of the corrugated tank is proposed. The structural behaviour of the fins is modelled using different structural models, such as the Euler-Bernoulli beam model and the Kirchhoff plate model, solved using the Ritz variational approach. In addition, fluid-structure interaction is studied to account for the compressibility effects of the confined fluid, which can affect volume and pressure variations. The results of these models are compared with Finite Element Method (FEM) simulations and experimental data. Corrections are proposed through sensitivity analysis of geometric parameters using FEM simulations.