| The oil-immersed transformer is the core equipment of the power system and the traction power supply system.Its long-term stable operation is the prerequisite for ensuring the safe and economic operation of the power supply system.According to statistics,insulation degradation is the primary cause of transformer failure,and most of the insulation degradation is caused by partial discharge.Partial discharge locating is helpful to improve the maintenance efficiency and optimize the transformer insulation design,so it is of great significance to locate the partial discharge of the transformer.Among them,the ultrasonic method has the advantages of high locating accuracy,strong anti-interference ability,and online detection,and is widely used in various electrical detection occasions.The problems that affect the locating accuracy of the ultrasonic method mainly include the ultrasonic propagation path,time delay estimation algorithm and locating algorithm.Around these three issues,the research done in this article is as follows:The principle of partial discharge generating ultrasound is systematically introduced by electro-mechanical-acoustic analogy Based on the built partial discharge locating platform and acoustic simulation research,the attenuation characteristics of ultrasonic waves and the propagation characteristics and propagation paths under complex structures are demonstrated,and the corresponding situation is obtained The calculation method of the next propagation time.The noise source of the partial discharge ultrasonic signal is analyzed.The EEMD algorithm is used to filter and de-noise.The signal envelope is extracted by cubic spline interpolation,and then the time-domain envelope characteristic parameters are obtained.The acoustic signal is divided into direct wave and non-direct wave,and the signal classification is realized by the support vector machine algorithm based on the envelope characteristic parameter.Finally,the preliminary determination of the location of the local discharge source is achieved through the cross direct area.After analyzing and comparing the experimental data,the LMSTDE algorithm with higher precision is selected as the delay estimation algorithm,and the DE-PSO algorithm is selected as the positioning algorithm.Taking the test transformer as the research object,a three-dimensional simulation model of the test transformer sound field is established,and the correctness of the model is verified by comparing with the experimental numerical value.Finally,through the actual measurement case,the process of partial discharge positioning method proposed in this paper is fully explained,and the results show that the positioning result error is small and the accuracy is high.In short,this paper combines the theoretical analysis,simulation modeling and actual measurement application research to analyze the ultrasonic propagation path in the transformer,selects a higher-precision delay algorithm and positioning algorithm,and finally achieves higher-precision partial discharge locating. |
