配电线路是配电系统的重要组成部分，我国的10-35kV的配电系统中性点多采用非有效接地方式，即中性点不接地或经消弧线圈接地。对于该系统中发生的配电线路单相接地故障，故障电流很小，故障特征难以辨别，保护构成困难。且目前配电线路结构多样，除广泛存在的单电源辐射状配电线路外，还有很多包含分布式电源的有源配电线路。到目前为止，还没有可靠、有选择性的单相接地保护方法在现场运行。本文针对配电线路的特点，提出了在多种供电场合下能够分区段切除单相接地故障的保护方案。论文的具体工作如下：1）详细分析了行波保护原理及其在配电线路中的适用性，分析了继电器出口处故障、配电系统分支线路等对于行波保护的影响，剖析了在配电线路中利用故障后初始电压电流行波构成行波保护的可行性。2）针对国内外大量存在的辐射状配电线路，分析故障行波在配电线路上的传播特性，提出了一种具备故障区段识别能力的单相接地保护方案，该方案在多分段的开环运行配电线路中可以有效区分故障区段，从故障线路两端切除单相接地故障。并针对不同的单相接地故障类型做了大量的EMTP故障仿真，验证所提保护方案的有效性。3）分析了分布式电源接入配电网对单相接地故障特征的影响，并提出了相应的单相接地保护方案，该方案不依赖于通信即可从故障线路两端切除单相接地故障。并利用PSCAD仿真软件验证所提保护方案的有效性。4）针对双断路器配置的双端供电配电线路，提出了相应的单相接地保护方案，方案可与方向过电流保护有效配合，实现单相接地故障的快速可靠切除。5）基于馈线保护装置TFP-101平台，利用C语言编写了所提算法的保护功能，参与装置的研发测试等工作，目前装置已在贵州凯里配电线路上挂网试运行。本文的研究工作大大提升了行波保护针对配电线路单相接地故障时的可靠性与选择性，使其在多种供电场合下均能够快速可靠地分区段将单相接地故障从线路两端切除，为尽快恢复非故障部分的供电创造了条件，有利于提高配电网自动化水平，也有利于分布式发电技术的进一步发展。
Distribution line is an important part of distribution system. The neutral of the 10-35kV distribution systems in China are mostly non-effective grounded, that is, the neutral is ungrounded or grounded using high impedance. When the single-phase-to-ground faults on distribution lines occur in such system, it is difficult to distinguish fault characteristics and protect the fault line because the magnitude of fault current is very small. At present, besides the widely existing radial distribution lines with a single source, there are many active distribution lines including distributed power source. The diverse structure of distribution lines makes it more difficult to protect such faults. So far, there is no single-phase-to-ground protection method which has the ability of identifying fault section in the field operation. In view of the characteristics of distribution lines, several protection schemes which can remove the single-phase-to-ground fault in section under various power supply situations are proposed in this paper. The specific work of this paper is as follows:1) The principle of traveling wave protection and its applicability in distribution lines are analyzed in detail. The effects of faults at the relay outlet and branch lines of distribution system on traveling wave protection are analyzed. The feasibility of traveling wave protection based on initial voltage and current traveling wave after fault in distribution lines is analyzed.2) Aiming at a large number of radial distribution lines in the world, the propagation characteristics of traveling wave on distribution lines are analyzed, and a single-phase-to-ground protection scheme which has the ability of identifying fault section is proposed. It can distinguish fault sections without relying on communication channels and remove single-phase-to-ground faults from both ends of fault lines. A large number of fault simulations for different types of single-phase-to-ground faults are done to verify the effectiveness of the proposed protection scheme by EMTP.3) The influence of distributed generation (DG) connecting to distribution network on the characteristics of single-phase-to-ground faults is analyzed, and the corresponding single-phase-to-ground protection scheme is proposed. The single-phase-to-ground fault can be removed from both ends of the fault line without relying on communication. PSCAD simulation software is used to verify the effectiveness of the proposed protection scheme.4) Aiming at the two-terminal power supply and distribution lines with double circuit breakers, the corresponding single-phase-to-ground protection scheme is proposed. The scheme can effectively cooperate with directional overcurrent protection to realize fast and reliable removal of single-phase grounding fault.5) Based on feeder protection device TFP-101 platform, the single-phase-to-ground protection function mentioned in this paper is realized by C language programming and tested.The research work in this paper greatly improves the reliability and selectivity of traveling wave protection for single-phase-to-ground faults on distribution lines, and it can quickly and reliably identify single-phase-to-ground fault section and remove the fault from both ends of the line in various power supply situations. It creates conditions for restoring the power supply of non-fault parts as soon as possible, which is conducive to improving the automation level of distribution network and also conducive to the further development of distributed generation technology.
