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Included angle selection for a V-shape insulator string applied in 750-kV compact transmission line is studied in this paper. The mechanical performance of V-shape insulator string is demonstrated from calculation and experiment. A new solution, which is based on the finite-element method and applied to calculate the deformation of V-string, is presented. This paper discusses the relation between deformation (displacements and force) and load on V-string. Loading experiment for V-string is conducted in order to verify the calculation results. Experimental data of displacements for V-shape composite and porcelain insulator string are obtained. Finally, combined with the calculation and experiment results, the selection of included angle for V-shape insulator string is discussed, and recommendations for the included angle value of V-shape insulator string in 750-kV compact transmission line are made.

Live working is important for the continuity of electricity supply in power system. Experiment results of 50% switching impulse sparkover voltages (U50) for different live working entering routes on a real tower are presented. The potential and electric-field distribution around the 750 kV straight tower window with a line worker inside, was analyzed via an approach combing charge simulation method and indirect boundary element method. The comparison demonstrates the close relationship between electric-field distribution and U50. The sparkover voltage and the maximum electric-field strength change synchronously for a specific structure. Generally speaking, the higher the electric filed strength is, the lower the sparkover voltage will be. Thus, the experiment procedure for deciding the best entering route can be simplified according to the electric-field distribution calculation.

PurposeThe purpose of this paper is to present a method to calculate the transient induced voltages along the underground pipelines and analyze the transient interference generated in the pipelines due to the inductive coupling in the fault‐to‐ground condition of power lines in close proximity.Design/methodology/approachBased on finite difference‐time domain method, an improved method is proposed to calculate transient inductive interference in underground metallic pipelines due to a fault in nearby power lines. The frequency‐dependent problem in the analysis of transient interference is solved in phase domain. Compared with the traditional method, the disposal of phase‐modal transformation matrices’ frequency‐dependent characteristic is avoided and the calculation is simplified by using vector fitting approach and recursive algorithm greatly in the proposed method.FindingsA novel improved method is proposed to calculate transient induced voltage distribution along underground metallic pipelines due to a fault in nearby power lines. Results show that the peak value of transient induced voltage at the most critical point is about 1.15 times of the magnitude in the steady state without the fault removed and the analysis of transient inductive interference is necessary in the fault‐to‐ground case of power lines.Practical implicationsIn order to mitigate the interference from power lines to nearby pipelines, pipelines should be good grounded and positioned as far away from the power line as possible. In high soil resistivity areas, the common corridor should be avoided.Originality/valueThe paper presents a method to calculate the transient induced voltages along the underground pipelines and analyze the transient interference generated in the pipelines due to the inductive coupling in the fault‐to‐ground condition of nearby power lines. The proposed method is general and can also be applied to other transient interference studies such as crosstalk problems of communication networks and interference between power lines and aboveground pipelines or communication cables. Effects of various parameters upon the inductive interference generated in underground pipelines due to a fault in nearby power lines are analyzed to be a guide for controlling the inductive interference.

In this paper, the electric-field distribution around the composite insulators and the heads of transmission towers is calculated by a model coupling the indirect boundary-element method to the moment method. The heterogeneous media, such as the composite insulators and the filament metal structures such as the transmission towers and the transmission lines, are considered altogether. The method can take into account not only the permittivity but also the resistivity of the media by using the complex resistivity in the frequency domain. The electric-field distribution around a three-phase 330-kV transmission tower with composite insulators was analyzed. The electric fields on the surfaces of the grading rings and the phase subconductors and at the ends of the composite insulators are analyzed. Both the method and the results are useful for the design of high-voltage transmission lines.