A Technique for the Optical Detection and Analysis of Dry Band Arcs on a Composite Insulator

Video cameras have been used in high voltage (HV) testing for many years, as they provide a convenient means of optically recording the events of a test. For example, high speed video cameras can capture pre-breakdown phenomena, and UV sensitive cameras can enable visualisation of corona discharge. However, the use of machine vision cameras in conjunction with real time image processing, creates not just a visual aid, but transforms the camera into a measurement instrument. This paper describes the implementation of a unique system into a salt fog chamber testing facility; as used for ageing and performance tests on HV insulators. The system provides three distinct benefits in dry-band arc observation. A synchronised leakage current trace and discharge image allow a direct comparison of the two, on a unified time scale. To make locating discharges on the insulator profile much easier, dry band arc images are superimposed onto a pre-captured image of the test object. Finally, the image is processed and broken down into regions of interest, enabling a spatial histogram of discharge occurrences to be produced.