Calibration of UV-sensitive camera for corona detection

[摘要] Electrical energy is continuously transported across the world by high voltage transmission lines. Thesetransmission lines are however subject to losses beside the inherent resistive and dielectric losses. Thisadditional loss phenomenon is described as corona. The CSIR has developed an optical system to detectthe radiation caused by the corona so that preventive measures can be taken to reduce these losses.The corona mechanism and how it results in measurable radiation is explored and the structure of the opticalsystem is analyzed. The optical emissions detected by the present optical system offer no indication of theseverity of the corona discharge. This issue is addressed in this thesis as correlations are sought betweenthe illuminated pixels displayed on the camera's display and physical quantities. A blackbody is employedto find a correlation between these illuminated pixels and radiation. Deviations from the correlation drawnis explored regarding the saturation mechanisms of the optical system and the distance from the blackbody.A corona cage is next employed to find a correlation between the illuminated pixels and electrical coronaloss, a quantity indicative of the severity of corona losses on a transmission line. Further tests are alsoperformed at a reduced gain as it was discovered that the optical system's response is more linear at reducedgain than at full gain. It is also indicated that this usage of reduced gain does not have a detrimental effect onthe sensitivity of the optical system. The corona cage measurement employs a small spheric source whichis taken as a base measurement against which all other measurements can be compared. The deviationof this base analogy is explored against deviations in the corona discharge geometry used, the prevalentweather condition, and the saturation of the optical system itself.Both the corona cage and blackbodies used are quite bulky pieces of laboratory equipment. The use of asmaller, more portable calibration source is therefore also explored. A literature study is made of lasers,lamp sources, and laser diodes that can be employed as a more portable calibration source. The final choiceof calibration source is shown to be a lamp source. Tungsten calibration lamps are explored in depth and acircuit is designed to keep the radiation from a lamp source constant in order to improve on its ability as acalibration source.

[发布机构] Stellenbosch University