Accurate Measurement Method for Distribution Parameters of Four-Circuit Transmission Lines with the Same Voltage Considering Earth Resistance

In response to the limitations of existing parameter measurement methods for four-circuit transmission lines of the same voltage—namely, the failure to account for earth resistance and the complexity of methods that hinder live-line measurements—this paper proposes a more accurate method for measuring the distribution parameters of such transmission lines, incorporating earth resistance. The paper derives the transmission equations, including earth resistance, from the standard transmission line equations for three-phase power lines. The symmetrical component method is employed to decouple the parameters, allowing the earth resistance, which is difficult to measure directly, to be expressed as a combination of positive and zero-sequence parameters that are easier to measure. Additionally, the phase-mode transformation matrix for the four-circuit line parameters is derived, enabling the diagonalization of the twelve-order parameter matrix for the four-circuit lines. This transformation matrix can then be applied to the voltage and current signals measured at both ends of the line, facilitating the determination of the voltage and current magnitudes. At each magnitude, the relationship between voltage and current conforms to the transmission equations of a single-circuit line. The proposed method is compared with traditional methods and improved traditional methods using PSCAD/EMTDC software (version 4.6.2). Furthermore, an adaptability analysis of the proposed method is conducted, considering variations in line length and theoretical initial values. The results demonstrate that the proposed method is suitable for measuring the distribution parameters of four-circuit transmission lines of the same voltage across a range of voltage levels and line lengths.