绝缘沿面缺陷是GIS设备内部常见缺陷，特高频法是对运行条件下GIS绝缘缺陷检测应用最广泛的手段。目前由于对缺陷劣化过程中的信号变化机理认识尚不明晰，导致放电特高频信号幅值无法直接和缺陷严重程度相关联，从而难以对缺陷劣化阶段进行合理划分。试验测量了绝缘沿面缺陷劣化过程中的特高频信号，并通过仿真探究了绝缘沿面缺陷特高频信号的变化机理，最后根据不同劣化程度特高频信号仿真结果提出了基于功函数归一化均值的沿面缺陷劣化程度划分方法。研究发现，劣化过程中绝缘表面功函数与特高频放电次数和均值都密切相关，利用功函数将特高频均值归一化后可以作为缺陷劣化阶段的划分标准，将缺陷严重程度分为低、中、高三类。经试验数据验证发现，所提方法能够对绝缘沿面缺陷劣化过程作出较好划分。研究成果为基于放电信号的缺陷严重程度评估奠定了理论基础。

Insulation surface defects are common defects inside GIS. The ultra-high frequency method is the most widely used to detect GIS insulation defects in operation. At present, due to the unclear understanding of the signal change during the defect degradation, the amplitudes of the UHF signals cannot be correlated with the severity of the defect directly, making it difficult to divide the defect degradation stages reasonably. An experiment is conducted to measure the UHF signals during the degradation of insulation surface defects and the change mechanism of the UHF signals is explored through simulation. Finally, according to the simulation results of UHF signals with different degradation stages, a method for dividing the degradation stage of surface defects based on the normalized mean of work function is proposed. It is found that the surface work function is closely related to the number of discharge pulses and the UHF mean value during the degradation. The UHF mean value normalized by the work function can be used as a criterion for dividing the defect degradation stages into three categories low, medium and high. It is verified that the proposed method can make a good division of the insulation surface defect degradation process through the experiment. The research results lay a theoretical foundation for defect severity assessment based on discharge signals.