基于等效负荷分支的配电网功率纵联保护方案

doi:10.19595/j.cnki.1000-6753.tces.251586

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摘要随着分布式电源的接入与不可测负荷分支的增加,配电网的故障特征发生了改变,导致传统单端量保护的死区问题难以避免。纵联保护以其优良的选择性和灵敏性在新型配电网中更具优势。然而,T接不可测负荷分支的存在使传统纵联保护方法的灵敏性与可靠性降低。因此,该文提出了基于等效负荷分支的功率纵联保护方法。首先,分析了传统功率差动保护适应性降低的原因;其次,结合配电线路与负荷的阻抗特征,提出了低数据同步需求的等效网络参数估计方法,分析了T接非线性负荷时的估算误差;然后,通过分析区内外故障不同条件下被保护线路两侧推算功率与测量功率的差值特征,构建了基于等效负荷分支的保护启动判据,有效降低了不可测负荷分支对保护的影响;最后,通过增设负荷投切识别判据避免保护误动。经仿真验证,在高比例新能源接入与大容量不可测负荷分支T接并网场景下,该保护方案能够灵敏、可靠地识别区内外故障,且具备较强的抗过渡电阻能力。

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关键词 ：纵联保护, 不可测分支, 等效网络, 同步性, 负荷投切

Abstract：With the large-scale integration of distributed generation (DG), traditional single-source radial distribution networks have evolved into complex multi-source power supply networks, resulting in significant changes in their fault characteristics. The sensitivity and reliability of traditional three-stage overcurrent protection are difficult to guarantee. Pilot protection, with its superior selectivity and sensitivity, demonstrates greater advantages in modern distribution networks. Considering engineering implementation costs, distribution networks permit loads to be connected as non-measurable branches in a T-configuration. Due to the current diversion effect of these non-measurable branches, traditional current or power differential protection faces a risk of maloperation during external faults or under normal operating conditions. Raising the protection threshold to account for the current of large-capacity load branches would significantly reduce protection sensitivity for internal faults. Therefore, to mitigate the impact of non-measurable branches on the protection scheme, this paper proposes a pilot protection method based on an equivalent load branch.
Firstly, the reasons for the reduced adaptability of traditional power differential protection following the T-connection of non-measurable load branches are analyzed, highlighting the dead-zone issue of conventional protection during metallic grounding faults at the line outlet. Secondly, by integrating the impedance characteristics of distribution lines and loads and based on the principle of star-delta equivalent network transformation, a network parameter estimation method with low data synchronization requirements is proposed using the phase voltage and current information from both ends of the protected line. The estimation error for T-connected nonlinear loads is analyzed, and an adaptive restraint setting method based on voltage variation characteristics is constructed. Then, by analyzing the difference characteristics between the calculated and measured power at both ends of the protected line under different voltage sag levels during internal and external faults, as well as the influence of fault output characteristics from external distributed generation sources on the protection, a protection initiation criterion based on the equivalent load branch is established. This effectively reduces the impact of non-measurable load branches on the protection. Finally, leveraging the differences in power factor characteristics between transition resistance and large-capacity loads, along with the difference characteristics between estimated and measured power under different fault types, a load switching identification criterion is introduced. This prevents protection maloperation and effectively enhances protection reliability.
Verified through PSCAD simulations and actual field fault recording data, the proposed protection scheme offers the following advantages: (1) It fully considers the influence of nonlinear load models, proposing an equivalent network parameter estimation method and a pilot protection criterion with low data synchronization requirements, thereby effectively reducing communication costs. (2) The protection scheme exhibits high reliability and sensitivity, featuring no dead zone for internal faults and no maloperation for external faults. With a protection threshold of 0.05 MV·A, it demonstrates a transition resistance withstand capability exceeding 250 Ω. (3) It fully accounts for the impact of load switching on protection. By incorporating a load energization identification criterion based on the active/reactive power difference ratio, it ensures the protection does not maloperation during scenarios involving high-capacity load energization. The effectiveness of this protection scheme has been validated in typical distribution network structures with varying distributed generation penetration levels, demonstrating considerable potential for engineering application.

Key words： Power pilot protection unmeasurable branches equivalent networks synchronism load switching

收稿日期: 2025-09-11

PACS:

TM614

基金资助:国家电网有限公司科技项目资助（5400-202455377A-3-2-ZX）

通讯作者: 赵玉枫男,1994年生,博士,讲师,研究方向为新型电力系统安全防御技术。E-mail：hdzyf@ncepu.edu.cn

作者简介: 李澳男,1999年生,博士研究生,研究方向为新型配电网安全防御技术。E-mail：1549762941@qq.com

引用本文:

李澳, 赵玉枫, 薛皓月, 王增平, 王彤. 基于等效负荷分支的配电网功率纵联保护方案[J]. 电工技术学报, 2026, 41(19): 6740-6752. Li Ao, Zhao Yufeng, Xue Haoyue, Wang Zengping, Wang Tong. Power Pilot Protection Scheme for Distribution Networks Based on Equivalent Load Branches. Transactions of China Electrotechnical Society, 2026, 41(19): 6740-6752.

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