高压电缆缓冲层烧蚀缺陷超声检测技术仿真研究

Simulation Research on Ultrasonic Detection Technology of Buffer Layer Ablation Defects in High Voltage Cables

近年来波纹铝护套结构高压电缆中出现的缓冲层烧蚀缺陷造成巨额经济损失和不良社会影响,然而该缺陷产生及发展机理尚不明确,检测技术仍处于探索阶段。文中基于缓冲层间隙放电导致烧蚀缺陷的理论,开展高压电缆缓冲层烧蚀缺陷产生超声信号特征研究,探索超声检测技术在缓冲层烧蚀缺陷检测领域的可行性。文中首先基于高压电缆结构特征以及缓冲层多孔介质特性,建立缓冲层多孔介质波模型以及缓冲层放电产生超声波模型。随后通过数值模型得到缓冲层放电产生超声波声压等效波形以及不同层数缓冲层在不同频率下的吸声系数,建立有限元仿真模型分析了缓冲层放电产生超声波的传播特性以及在电缆外护套处的检测信号灵敏度。若放电发生在缓冲层内层,难以通过超声检测技术检出该信号,在波纹铝护套波谷处产生较为强烈的放电时,具有通过超声技术检测该信号的可行性。

In recent years,ablation defects found in the buffer layer of HV corrugated aluminum sheathed cables have caused severe economic loss and bad influence on society.However,the generation and development mecha⁃nism of this kind of defect is unclear so far and the detection technique is still in the exploratory stage.In this paper,the study of ultrasonic signal characteristic due to ablation defect in the buffer layer of high voltage cables is per⁃formed on the basis of the theory that gap discharge of the buffer layer leads to ablation defect so to explore feasibility of ultrasonic detection technology in the detection field of ablation defect of the buffer layer.In this paper,multiple porous media wave model of the buffer layer and the ultrasonic wave model due to discharge of the buffer layer are set up firstly on the basis of structural characteristic of high voltage cable and multiple porous media characteristic of buffer layer.Then,the equivalent waveform of ultrasonic wave sound pressure due to discharge in buffer layer and the sound absorption coefficient of buffer layer with different number of layers at different frequencies are obtained through the numerical model.The propagation characteristics of ultrasonic wave generated by the discharge in buffer layer and its detection signal sensitivity at the cable sheath are analyzed by way of setting up a finite element simula⁃tion model.In case discharge in the inner layer of the buffer layer,it is difficult to detect the signal through the ultra⁃sonic detection technology.In case of strong discharge at the valley of the aluminum sheath,it is possible to detect the signal through the ultrasonic detection technology.