基于相位差的小电阻接地有源配电网接地故障保护算法

doi:10.19595/j.cnki.1000-6753.tces.231742

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摘要大规模分布式电源（DG）接入小电阻接地系统配电网后,故障电流产生明显变化,采用零序电流保护方法切除单相接地故障将出现误动作。为了解决以上问题,首先,提出基于相电压与零序电流相位差的小电阻接地系统有源配电网接地故障保护算法;然后,通过建立包含多个分布式电源的配电网接地故障电气系统结构与模型,对故障时刻相电压与零序电流相位关系进行理论推导与计算,分析得出不同接地故障位置的相位差区间,根据相位差区间进行接地故障判断与保护;最后,进行仿真验证,结果表明该方法在配电网中性点采用小电阻接地系统时,在多种过渡电阻,不同分布电源接入数量与容量,各类型电缆长度等情况下,负载波动,均能可靠判断接地故障,适用于DG中性点经小电阻接地和不接地两种方式。

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	李君
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	黄守道
	刘君
	刘志勇

关键词 ：有源配电网, 相电压与零序电流, 相位差, 小电阻接地系统, 单相接地保护

Abstract：After the large scale distributed power supply is connected to the distribution network of the small resistance grounding system, the fault current changes significantly, which affects the original grounding protection accuracy of the system, zero-sequence current protection method is used to remove the single-phase ground fault. In recent years, experts and scholars have put forward the zero-order current phase differential protection scheme, pearson correlation protection method and zero-sequence current centralized comparison method, which is necessary to collect the zero-order current amplitude or phase of different monitoring points to upload it to the main station to calculate the fault location, which depends highly on communication and main station algorithm. In order to solve the above problems, the grounding fault protection algorithm of small resistance grounding system based on phase voltage and zero sequence current is proposed.
By establishing the structure and model of the distribution network grounding fault electrical system containing multiple distributed power sources, we theoretically derive and calculate the phase voltage and zero sequence current at the time of failure, by calculating the phase difference between different grounding fault positions and different grounding transition resistances. Analyzing the phase difference interval characteristic value of ground boundary fault, outboundary fault and DG outboundary fault, according to the interval eigenvalue, the protection algorithm is implemented by: Real-time acquisition and calculation of zero-order current amplitude, when its effective value is 3I_n>I_set, start the protection calculation; real-time acquisition and calculating phase voltage amplitude, compare the three-phase voltage amplitude, select the phase with the amplitude drop as the fault phase; calculate the phase difference between the fault phase voltage and the zero-order current in real time, when the phase difference θ_UC∈ (-10°, 40°), is the power side boundary fault, protect the instantaneous action. When the phase difference θ_UC∈ (80°, 130°), is the no fault line or no DG fault line, is an extra boundary fault; when the phase difference θ_UC∈ (150°, 230°), after the fault point with DG, Or a no fault line with a DG, is the DG external failure, protection time-delay action. The phase difference between fault phase voltage and zero sequence voltage is affected by transition resistance, neutral grounding resistance and line distribution parameters. When the capacitor current of the power grid reaches the extreme 700 A, the fault range within the boundary is expanded from (0.5°, 14.8°) to (-6.5°, 33°). In order to improve the adaptability of the criterion in extreme cases and consider a certain margin, the accuracy of the criterion is not affected, and the action angle of the protection criterion is larger than the calculation result.
After simulation verification, the following conclusions are drawn: (1) The algorithm can accurately judge the power side boundary fault, extra boundary fault and DG external failure. Applicable DG neutral point by the small resistance grounding and not grounding two ways. (2) The algorithm can accurately judge the grounding fault in different grounding transition resistance conditions. Transition resistance up to 3 kΩ. At the different numbers of DG, different DG short-circuit capacity, different cable lengths, With load fluctuations and other on, can accurately judge the grounding fault. (3) The algorithm realizes the grounding fault judgment inside the protection device, without communication with the main station or device to achieve fault judgment, not affected by communication. (4) No need to install a zero-sequence voltage transformer, phase voltage can be obtained by electric field induction, the phase voltage can also be obtained by taking the capacitance of the circuit breaker on the primary and secondary deep fusion column, zero-sequence current can be synthesized by three-phase current, can be adapted to the type fault indicator scenario. It can also be applied to the circuit breaker scene on the primary and secondary fusion column.

Key words： Active distribution network phase voltage and zero sequence current phase difference small resistance grounding system single phase grounding fault protection

收稿日期: 2023-10-18

PACS:

TM77

基金资助:国家重点研发计划资助项目（2020YFB0906000）

通讯作者: 李君男,1981年生,博士研究生,研究方向电力系统安全监测与主动防御技术。E-mail：568232496@qq.com

作者简介: 何敏女,1977年生,研究员,博士生导师,研究方向为复杂电力系统控制技术。E-mail：hemin607@163.com

引用本文:

李君, 何敏, 黄守道, 刘君, 刘志勇. 基于相位差的小电阻接地有源配电网接地故障保护算法[J]. 电工技术学报, 2024, 39(23): 7418-7429. Li Jun, He Min, Huang Shoudao, Liu Jun, Liu Zhiyong. Grounding Fault Protection Algorithm of Small Resistance Earthing Active Distribution Network Based on Phase Difference. Transactions of China Electrotechnical Society, 2024, 39(23): 7418-7429.

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