Research On UHV DC Transmission Line Audible Noise And Corona Discharge Test

With the development of UHVDC transmission, transmission lines electromagnetic environment becomes a problem that must be considered in circuit design process.Audible noise and corona discharge are important assessment indicators of DC line electromagnetic environment.Based on this, this paper studied audible noise and corona discharge phenomenon of DC transmission lines.The main work is as follows:Based on large outdoor cage corona in UHV DC test base ofthe State Grid Corporation, relevant test methods of corona audible noise were studied.The results show that,we can use a single positive test corona cage instead of a bipolarone when carrying out an audible noise test.It caneffectively reduce the impact of ground reflection on the test results to lay sound absorbing materialon the ground.Data of different test probes can mutually verifiable the effectiveness.According to the corona cage audible noise test methods, we draw the relationshipbetween audible noise and electricfield strength on wire surface.To further analyze the characteristics of corona audible noise, we need to distinguish corona noise from the environmental noise. Based on spectral envelope area and spectral irregularity, we performed experiments on corona noise spectrum and environmental noise spectrum of low, medium, high frequency and studied characteristics of environmental noise and audible noise spectrum under different voltage levels Research indicates that spectral envelope area of high frequency can effectively differentiate the corona noise and environmental noise. High frequency spectral envelope area, middle frequency spectral envelope area and its spectrum irregularity can be used to distinguish different wire corona discharge status. Data with smaller spectral envelope area and spectrum irregularity can be selected when researching audible noise under a certain voltage level.Finally, we studied corona discharge phenomena at high altitudes in western China. According to UV imaging detection technology, we tested the discharge photons changes in corona discharge process. By studying the attenuation law of discharge photon in the spread on the air, we obtained the formula to calculate the number of photons at discharge point using ultraviolet imager test results. And then we perform a comparative study of the changing properties of the photon number and onset voltage on the positive and negative transmission line, which has a certain significance on the application of UV imaging technique to detect corona discharge phenomenon.