An efficient analytical based technique to numerical calculation of extended earth return impedance and admittance of overhead lines

This paper describes an efficient numerical integration technique for the extended overhead line earth return impedance and admittance formula. In-appropriate handling of the infinite integral in the formula can lead to erroneous calculated earth-return parameters at extreme frequencies, and a significant increase in computational effort. In this paper, an efficient technique based on an analytical approach is introduced to enforce proper discretization of the extended transmission line equations. Firstly, the line equations are analyzed, and a common cause of improper discretization is identified. Then the equations are further broken down numerically, based on which a procedure to suitably select a discretization interval and step is developed. Validation was conducted by calculating the earth return parameters of overhead-line cases using the proposed method and equal distance discretization. The proposed technique shows accurate results while using fewer discretization points than equal distance discretization.