Ultraviolet Detection Of Partial Discharge At The Surface Of Power Transmission And Transformation Equipment And Its Application

Under the long-term influence of electrical,thermal,force and physical environment factors,the decline of electrical,mechanical and other properties of the insulation of power transmission and transformation equipment will result in aging and damage,which will affect the safe and stable operation of the insulation of power transmission and transformation equipment.The detection of partial discharge characteristics on the insulation surface of power transmission and transformation equipment is helpful to find defective insulation in time,facilitate the operation and maintenance of the insulation of power transmission and transformation equipment,and prevent the occurrence of major safety accidents caused by insulation damage.Ultraviolet imaging technology is widely used in the operation and maintenance of power systems because it is convenient and quick to detect the partial discharge characteristics on the insulation surface of power transmission and transformation equipment.In this paper,based on the theory of partial discharge on the insulating surface of power transmission and transformation equipment and the principle of ultraviolet imaging detection,through the analysis of the ultraviolet image characteristics of partial discharge on the insulating surface,the ultraviolet image processing algorithm was studied and realized by programming.Simulation and experimental method are used to study the electric field distribution and partial discharge along 220 k V insulators under different conditions.Finally,ultraviolet imaging technology is used to analyze the results of insulation ultraviolet detection of the primary side equipment of a substation.The details are as follows:(1)Based on the theory of partial discharge on power equipment insulation and the ultraviolet detection method,the characteristics of ultraviolet imaging on the insulating surface of power equipment are analyzed.The wavelength of the optical signal creating by the partial discharge on the power equipment insulation is within the wavelength observation range of the solar-blind ultraviolet imager.The intensity of the partial discharge at the insulation surface of power equipment can be judged by the number of photon and the feature of the ultraviolet image.(2)Based on the modern image processing technology and the characteristics of the UV image of partial discharge phenomenon,the algorithm of image segmentation,filtering and noise reduction and spot area calculation for the UV image of partial discharge on the insulating surface of power transmission and transformation equipment is studied,and the related program is written.The number of photons detected in UV and spot area in UV image during partial discharge on the surface of the glass insulator can be increased by fouling and increasing the external construction frequency voltage,which verifies the rationality of the proposed algorithm.(3)Experiments and simulation method are used to study the surface partial discharge intensity of 220 k V silicone rubber insulator string and porcelain insulator string under different conditions.The surface electric field of 220 k V silicone rubber insulator string can be significantly reduced and the intensity of partial discharge can be weakened by adding the uniform ring;the effect of the uniform ring at the high voltage end is more significant than that of the uniform ring at the low voltage end;the cracking of voltage equalizing ring has little effect on the surface electric field distribution and partial discharge intensity of 220 k V silicone rubber insulator string;both pollution and damage will affect the surface electric field characteristics of the insulator and increase the partial discharge intensity on the surface of the 220 k V porcelain insulator string.However,the defect types cannot be effectively distinguished by the number of photons detected by UV.(4)Ultraviolet detection was carried out on the power equipment of a 220 k V indoor substation in Hubei province.According to “DL/T345-2019 Application Guidelines of UV Diagnostic Technology for Live Electrical Equipment”,the number of ultraviolet detection photons of partial discharge on the insulation surface of different power transmission and transformation equipment was uniformly calibrated to the standard test distance.It is found that the number of photons detected at the hanging insulator string in AC phase station,the high voltage terminal of voltage transformer and the metal connection of phase A through wall bushing are all larger than 8000,which belongs to high intensity discharge section.The number of photons at other detection positions is in the range of 1000～8000,which belongs to moderate intensity discharge section.Infrared detection of power transmission and transformation equipment should be further carried out,and partial discharge intensity and insulation status of power equipment should be judged based on infrared detection results,so as to determine the type of insulation defects and equipment operation status in time.