Corona Discharge Detection with Modified Consumer Cameras

Corona discharges are a type of partial discharges (PD) on the surface of conductors. They are a common problem in high-voltage transmission systems and switch-gear due to the high electric field strength. Because of the emitted ozone and ultraviolet (UV) radiation, corona discharges lead to the degradation of polymeric insulators. They also generate undesired audible noise and radio frequency interference. Special cameras are available for the detection and localization of corona discharges on overhead lines and in air insulated substations. However, these cameras usually work with a beamsplitter, separate sensors for visible and UV light, highly UV transmissive quartz optics and solar-blind filters to be used in the day time. This makes them rather expensive. In this paper a modified consumer camera is presented as an alternative to specialized corona cameras. Regular digital camera sensors are naturally sensitive for UV (and infrared) radiation and can be used to detect discharges. Because of the adverse effects on the image quality, manufacturers usually implement filters on the sensor to block the UV light. These filters can be removed to greatly enhance the sensitivity of the camera. This paper aims to compare the two different technologies and their strengths and weaknesses and show some application examples.