Porcelain suspension insulators are widely used in the power system to provide electrical insulation and mechanical support for high voltage transmission lines. To detect and replace the faulty insulators on power transmission lines is of great importance for safe operation of the power system. The utilities detect the faulty one by measuring the voltage across the insulators or by observing the cracks. It is a time-consuming method. In this paper, developed field analysis using finite element method and asymptotic boundary conditions is reported. It reveals that the electric field near the good insulator is quite different from that of the faulty one. The ratio of r and z components of the electric field is significant to characterize the faulty insulator. Experimental measurement with Pockels field sensor verified the analysis. This new method can enhance the speed and safety of detecting faulty insulators in an operating power transmission line.
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