基于频域热特征成像的复合绝缘子缺陷检测方法

Defects Detection Method for Composite Insulators Based on Frequency Thermal Characteristics Imaging

为了消除复合绝缘子内部缺陷对电力系统安全运行的潜在威胁,提出一种基于频域热特征成像的复合绝缘子检测方法。该方法对被检测绝缘子施加脉冲热激励,并采集其表面动态变化温度分布,利用离散傅里叶变换分析其表面温度变化信息的频域特征,通过识别幅值图和相位图序列中的异常区域以检测内部缺陷。通过对复合绝缘子不同深度的护套孔隙和分层缺陷的检测试验证实了低频段频域热图对深度较大缺陷的检测优势。最后,分析了不同深度缺陷差分相位谱的变化规律,并利用差分相位谱的盲频特征估计了缺陷的深度。相比于其他缺陷检测技术,该方法具备非接触测量、检测速度快、结果形象直观、可定量测量的特点,具有广阔的应用前景。

In order to eliminate the potential threat of the composite insulators with internal defects to the safe operation of power systems, a detection method for composite insulators based on frequency thermal characteristics imaging was presented in this paper. In this method, the inspected insulators were excited by a heat pulse while the dynamic surface temperature distribution was recorded by an IR camera.Discrete Fourier transformation was used for analyzing the frequency domain characteristics of the surface temperature change, and the defects can be detected by identifying the abnormal regions in amplitude and phase thermal image sequences. The porosity and delamination defects at different depths in the sheath of composite insulators were detected by experiments, which proved the advantage of low frequency-domain thermal images in detecting the deeper defects. Finally, the variation laws of the differential phase spectra of the defects with different depths were analyzed, and the blind frequency in differential phase spectrum was used to estimate the depth of the defects. Compared with other defect detection technologies, pulsed phase thermography has a broad application prospect, with the characteristics of non-contact measurement, fast detection speed, visual results and quantitative measurement capability.