A generalized FEM-based framework for earth return impedance calculations on vertically-multilayered media

Accurate modeling of earth return impedance is essential for assessing electromagnetic interference (EMI) in pipelines near overhead transmission lines (OHL). Conventional models, limited by assumptions of homogeneous or horizontally stratified soils, often subestimate EMI risks. This paper introduces a finite element method (FEM)-based approach to calculate self and mutual impedances in vertically stratified soils, overcoming limitations of analytical models. Compared with homogeneous cases, the FEM approach demonstrates improved accuracy, with impedance values reflecting real soil complexities. A case study with a 150 kV OHL near an underground pipeline highlights the efficacy of the proposed framework in capturing EMI effects in complex soil environments.