Three-Dimensional Boundary Element Method and Finite Element Method Simulations Applied to Stray Current Interference Problems. A Unique Coupling Mechanism That Takes the Best of Both Methods

In this paper it will be demonstrated how a boundary element method (BEM) model based on so-called pipe elements and a finite element method (FEM) model that is limited in space can be coupled to study local effects on 3D structures in half space. The main idea is to replace the original 3D structure with an “equivalent pipeline network,” which is used in the BEM model to calculate the complete direct current (DC)-traction interference problem. In the FEM code on the other hand, an “equivalent bounding box” that surrounds the complete 3D structure is defined. The potential distribution on this bounding box is calculated using the BEM model and applied as boundary condition for the actual FEM calculation on the original 3D structure. This new approach is applied and validated on a typical underground car park geometry made of steel sheet walls that exhibits stray current interference from a neighboring DC-traction system. It has been demonstrated that this unique coupling technique works very well and allows the modeling of local effects on 3D structures influenced by large DC-traction systems.