电工技术学报  2023, Vol. 38 Issue (13): 3539-3551    DOI: 10.19595/j.cnki.1000-6753.tces.220473
电力系统与综合能源 |
不接地系统异名相两点接地故障工频电气量及其对选线的影响分析
亓志滨1, 田君杨2, 薛永端1, 蔡卓远1, 徐丙垠3
1.中国石油大学(华东)新能源学院 青岛 266580;
2.广西电网电力调度控制中心 南宁 530023 3.山东理工大学智能电网研究院 淄博 255049
Analysis of Power Frequency Electrical Quantity and Line Selection Applicability for Two-Point Grounding Faults Occurring on Different Phases in Isolated Neutral System
Qi Zhibin1, Tian Junyang2, Xue Yongduan1, Cai Zhuoyuan1, Xu Bingyin3
1. New Energy College China University of Petroleum (East China) Qingdao 266580 China;
2. Guangxi Power Grid Power Dispatching Control Center Nanning 530023 China;
3. Research Center for Smart Grid Shandong University of Technology Zibo 255049 China
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摘要 中性点不接地系统异名相两点接地且至少一个故障点过渡电阻较大时,故障电流较小出线保护不能直接切除,仍需依赖接地故障选线装置实现保护。根据故障边界条件建立不接地系统异名相两点接地故障复合序网,利用节点阻抗矩阵分别推导出两个接地点故障电流、系统零序电压等工频电气量随两个接地点过渡电阻的变化规律,并进一步分析了其对现有选线技术的影响。结果表明,异名相两点高阻接地时工频电气量总体特征与传统小电流接地故障特征相近,零序电压一般介于两个故障点单独接地时的零序电压之间,其中两个故障线路出口的零序电流既不符合故障线路特征也不符合健全线路特征,已有稳态选线原理并不完全适用。最后,利用数字仿真和现场数据验证了理论分析的正确性。
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亓志滨
田君杨
薛永端
蔡卓远
徐丙垠
关键词 中性点不接地系统异名相两点接地工频电气量稳态选线    
Abstract:In isolated neutral system, when two-point grounding faults occurring on different phases take place and at least one of the transition resistances is large, the outgoing protection with the small fault current can not be directly removed, it still need to rely on the line selection device to achieve protection. At present, there are some problems in the research on the two-point grounding fault of the small current grounding system, such as lack of quantitative analysis, lack of line selection effect analysis, and difficult to be applied in practice et al. To address these issues, based on the fault equivalent circuit, this paper analyzes the power frequency fault characteristics for two-point grounding faults occurring on different phases in isolated neutral system. Based on the fault characteristics, the adaptability of the existing power frequency line selection methods to the two-point grounding fault of the different phase is analyzed and the development suggestion of line selection technology is put forward.
Firstly, Setting up the compound sequence network of two-point grounding faults occurring on different phases, using the nodal impedance matrixes to respectively deduce the expressions of power frequency components, such as two grounding fault point currents, zero-sequence voltage, and so on. Secondly, analyze the characteristics of two-point grounding fault power frequency electrical quantity with the change of the transition resistances in ungrounded systems and compare them with the characteristics of single-point grounding faults. Finally, according to the fault characteristics, the limitation of the existing line selection methods are analyzed, and the development ideas of two-point grounding fault line selection technology are put forward.
The results show that, when the transition resistance of at least one fault point is large, the amplitudes of zero-sequence voltage and zero-sequence current of power frequency in two-point grounding of the different phase show the characteristics of single-point grounding. At least one fault feeder has a power frequency zero-sequence current amplitude greater than that of the healthy feeder. The phase relationship of zero-sequence current of power frequency between the fault feeder and health feeder depends on two fault phase sequences, transition resistance of two fault points and total capacitance to the ground of the system. Generally, there is no definite phase relationship. In general, the zero-sequence voltage amplitude when two fault points are grounded is between the zero-sequence voltage when two fault points are grounded separately. When the transition resistance of two fault points is similar, the zero-sequence voltage when two fault points are grounded is minimum. For two-point grounding faults occurring on different phases in isolated neutral system, the zero-sequence voltage starting criterion still has high resistance to transition resistance and can reach the threshold value in most cases.
The zero-sequence current at the outlet of two fault lines generally does not conform to the characteristics of both fault feeder and healthy feeder, and the existing line selection principle is not fully applicable. When the amplitude and phase information are used for line selection, missing selection or rejection will occur.
Development suggestions of line selection technology: (1) As for the development of steady-state line selection technology for two-point grounding fault, based on the conclusions of power frequency characteristics, the change of power frequency characteristics of faulty line and non-faulty line before and after subsequent fault, or the change of power frequency characteristics of faulty line and non-faulty line before and after first fault line removal can be further studied. According to the difference of power frequency characteristics between fault line and non-fault line in two stages, two-point grounding fault detection is realized and the detection time is further shortened to improve detection efficiency. (2) As for the development of transient line selection technology for two-point grounding fault, based on the conclusions of power frequency characteristics, the intermittent arc grounding process after subsequent fault can be analyzed.
Key wordsIsolated neutral system    two-point grounding faults occurring on different phases    power frequency components    the steady-state line selection   
收稿日期: 2022-04-01     
PACS: TM713  
基金资助:国家自然科学基金项目(52077221)和南方电网公司科技项目(046000KK52220008)资助
通讯作者: 田君杨 男,1981年生,博士,高级工程师,研究方向为电力系统继电保护与优化运行。E-mail:sumtjy@163.com   
作者简介: 亓志滨 男,1998年生,硕士研究生,研究方向为配电网接地故障检测与保护。E-mail:qizhibin90@126.com
引用本文:   
亓志滨, 田君杨, 薛永端, 蔡卓远, 徐丙垠. 不接地系统异名相两点接地故障工频电气量及其对选线的影响分析[J]. 电工技术学报, 2023, 38(13): 3539-3551. Qi Zhibin, Tian Junyang, Xue Yongduan, Cai Zhuoyuan, Xu Bingyin. Analysis of Power Frequency Electrical Quantity and Line Selection Applicability for Two-Point Grounding Faults Occurring on Different Phases in Isolated Neutral System. Transactions of China Electrotechnical Society, 2023, 38(13): 3539-3551.
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