Sphere gap was widely used in measuring high voltage. However, in some cases, such as distribution voltage measuring of insulators, sphere gap did not work well for its too-large self-capacitance.

A new method of measuring the distribution voltage of insulators has been established.

In this paper, the distribution voltage of a section of insulators has been induced by a drainage ring to a pair of needle electrodes, which was made of tungsten and had a 20μm tip radius [1]The gap between the two needle electrodes were 1mm, 2mm and 3mm.The relationship between the sustained voltage, including the distribution of insulators and the discharge phenomenon the distribution of insulators and the discharge phenomenon, has been found on two aspects: discharge frequency and discharge intensity[2].

. The discharge frequency was obtained by recording the current flowed the needle electrodes and analyzing the recorded data. The discharge intensity was defined by the grey scale of the discharge photograph obtained by a high resolution camera. With this novel method , the distribution voltage along the insulators, including ceramic insulators, glass insulators and composite insulators can be easily and precisely measured ,which contributes to the study of the electric properties of insulator. Therefore, failures of insulators caused by unevenly distributed voltage can be avoided by innovating design of insulators.