伴随着我国双碳目标下的能源战略转型，配电网由传统的电能分配载体转变为源荷储协调枢纽平台，对供电可靠性的要求显著提高。单相接地故障是中性点非有效接地配电网最常见也是保护正动率最低的故障类型，特别是单相接地往往伴随着较长的发展过程，现有的故障检测与保护方法难以快速处理，导致形成永久性接地故障甚至进一步恶化为相间短路故障，严重影响了配电网的安全可靠供电。本文选取电缆局部绝缘缺陷劣化和架空线单相触树这两种最典型的发展性故障作为研究对象，分别开展了机理分析、建模以及故障辨识的研究。主要工作包括：（1）分析了电缆局部绝缘缺陷劣化发展性故障机理，建立了基于控制论的暂态振荡间歇性电弧模型、基于电损伤理论的半稳态间歇性电弧模型和基于能量平衡方程的稳态间歇性电弧模型，完备表征了绝缘劣化各发展阶段随机性、间歇性等故障特性。（2）分析了架空线单相触树发展性故障机理，针对导电通道中接触点、树干、树皮表面电弧分别建立了热交换引发的空气间隙击穿扩大模型、考虑温度和含水量的圆柱体电阻模型以及沿树干发展的电弧模型，有效表征了各导电通道在每个发展阶段的故障特性。（3）归纳了故障发展过程中典型故障特征，定量计算了不同故障距离衰减对保护安装处感知的暂稳态电气特征量的影响。（4）提出了一种基于零序电压回归线斜率过零频率的电缆局部绝缘缺陷劣化发展性故障辨识方法和一种基于零序电流回归线斜率过零间隔的架空线单相触树发展性故障辨识方法，不受系统参数不对称和间歇性电弧引起的零序电流波动的影响，仿真及实测故障数据验证了方法的有效性。本文所提方法可以在发展性故障形成永久性故障前识别并切除故障，同时根据辨识出的故障诱因指导运维人员快速巡线处理故障隐患点，对于降低配网事故风险、减少线路隐患具有积极意义。
The distribution network is converted from a standard power distribution carrier to a source-load-storage coordination hub platform in tandem with the energy strategy‘s transformation under China‘s dual-carbon objective. This greatly enhances the need for power supply dependability. In non-effectively grounded distribution networks, single-phase grounding faults are the most prevalent fault types and have the lowest probability of correct protection. In particular, single-phase grounding is frequently associated with a lengthy development process, making it challenging to propose prompt fault detection and protection methods. This can lead to the formation of permanent grounding faults or, even worse, deterioration into phase-to-phase short-circuit faults, which can have a major impact on the safety and reliability of the distribution network‘s power supply. In this thesis, the two most typical developmental faults, cable insulation local defect degradation faults and overhead line single-phase tree contact faults, were chosen as research objects. Mechanism analysis, modeling, and fault diagnosis were conducted thoroughly. The major work consists of the following sections:(1) The mechanism of cable insulation local defect degradation faults was investigated. The oscillatory intermittent arc model based on cybernetics, the semi-steady-state intermittent arc model based on insulation degradation theory, and the steady-state intermittent arc model based on the energy balance equation were established. The fault characteristics of randomness and intermittency in each developmental stage were fully characterized.(2) The mechanism of overhead line single-phase tree contact faults was analyzed. The air gap breakdown expansion model based on heat exchange, the cylinder resistance model considering temperature and water content, and the arc model along the trunk were established for the contact point, trunk, and arc on the surface of the trunk in the conductor‘s path. The proposed models effectively characterized the fault characteristics of the conductor‘s path in each developmental stage.(3) The typical fault characteristics during fault development were summarized. The effects of different fault distance attenuation on the amount of transient-state and steady-state electrical characteristics perceived at the protection installation were quantitatively calculated.(4) A developmental fault identification method based on the frequency of the zero-sequence voltage regression line slope over zero for detecting the cable insulation local defect degradation faults and a developmental fault identification method based on the time interval of zero-sequence current regression line slope over zero for detecting overhead line single-phase tree contact faults were proposed. The proposed methods were not affected by the fluctuation of the zero-sequence current caused by asymmetrical system parameters and intermittent arcing, and the measured fault data verified the validity of the methods.The developmental fault identification methods proposed in this paper can identify and clear the faults before they develop into permanent faults. Additionally, the identified fault cause can guide the maintenance personnel to patrol the lines to deal with the hidden faults, which is helpful for reducing the risk of distribution network accidents and addressing the hidden problems of the lines.
