Influence of insulating layer and proximity effect in overhead line capacitance matrices

In this paper, a numerical soluction based on the method of moments is used to compute the external parameters of hybrid systems composed of bare and coated cables commonly used in overhead lines. The considered formulation is more efficient than calculation methods based on the finite element method, which requires the discretization of the whole computational space. Also, it is more rigorous than routines available in electromagnetic transient simulators, which neglect the proximity effect. Application examples considering closely-spaced cables are used to illustrate the influence of insulation, relative permittivity of the insulating layer, and cable separation on per-unit-length capacitance matrices. These examples are also used to test the validity of a simplified formulation used to calculate overhead cable parameters in popular electromagnetic transient simulators.