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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]