Corona Partial Discharge Detection With A Modified Raspberry Pi Camera Prototype
Philipp Elfers, Johannes Friedrichs, Sebastian Azer, Philip G. Born · 2024
Corona partial discharges are a common challenge in power grids which can cause degradation of insulation materials. In the worst case, this leads to a breakdown and failure of the insulation system of grid components like switchgear, bushings, instrument transformers or power transformers. As an alternative to electrical measurements or acoustic detection methods, corona partial discharges can be detected with optical camera systems. Due to generation and recombination processes in air insulated equipment, photons mostly within the ultraviolet spectrum are emitted which are invisible to the human eye. For the optical detection of partial discharges in air under daylight conditions, special camera systems are required. The availability of commercial camera systems for corona partial discharge detection is limited by a small number of suppliers leading to challenging economic situations for the potential user. Typically, they are complex instruments containing integrated optics and separate sensors for the visible and the ultraviolet spectrum. Therefore, a new approach has been tested by using a modified Raspberry Pi camera sensor and mirror optics. A Raspberry Pi camera sensor has been turned sensitive to ultraviolet light by chemical and mechanical modification. This camera prototype has been tested under AC-conditions in an high voltage laboratory and a corresponding electrical partial discharge measurement following IEC 60270. The UV-images captured by the modified camera sensor are correlated to the events measured with the electrical partial discharge measurement system. The Raspberry Pi camera prototype is capable of detecting corona discharges as low as 7.5 pC up to several nC at distances of 2 m. Higher PD-activity such as increasing apparent charge levels and impulse repetition rates are linked to brighter events on the camera screen due to more photons detected on the camera sensor. This paper introduces a new approach of a corona partial discharge detection camera system using a modified Raspberry Pi camera sensor.