Influence of local, frequency-dependent grid and earthing impedances on the current distribution in the earth and earthing system

本地频率相关电网和接地阻抗对大地和接地系统中电流分布的影响

• 批准号: 521916793
• 负责人: Professor Dr.-Ing. Uwe Schmidt
• 金额: --
• 依托单位: Fakultät Elektrotechnik- und Informatik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/521916793?language=en
• 关键词: Influence; local; frequency; dependent; grid

The neutral point treatment in connection with the design of earthing systems is an essential part of the measures to comply with personal safety in the operation and planning of electrotechnical systems and networks. It has an effect on the dimensioning of medium and high-voltage networks in particular. Compliance with the normative requirements in the event of earth fault currents and the resulting touch voltages is obligatory. The dominant neutral point treatment in power systems with nominal voltages up to and including 110 kV is resonant neutral point earthing (RESPE). The advantage of this neutral point treatment is very low (residual) earth fault currents and the associated low touch voltages in the event of a fault. Measurements in recent years show that high proportions of harmonic currents often dominate the residual earth fault current. This leads to controversial discussions about the influence of harmonic currents on the design of earthing systems. The measures of the current normative standard always refer to rms values and are formulated in relation to the nominal grid frequency (50 Hz). The differentiated handling of components of higher frequency is not defined. Taking these into account requires additional measures and leads to the expectation of impermissible touch voltages. If the frequency-dependent current distribution in the earthing system is known, it may be possible to neglect harmonic components of the potential-raising current. This significantly reduces the effort required to comply with the touch voltage. Within the scope of the research project, the frequency-dependent current distribution in the earthing system is investigated. Based on measurements in distribution networks up to and including 110 kV, a model is developed to describe the locally distributed, frequency-dependent impedances and the effective current loops in the event of an earth fault. The frequency-dependent current distribution in the earth and earthing system is fundamentally described. By developing mathematical procedures for mapping this current distribution, resulting reduction factors for the earth current and earth voltages are calculated. A worst-case consideration for any distribution network configurations is derived. The University of Applied Sciences Zittau/Görlitz has been involved in the technical work of the committees in a leading role for many years. The Chair of Electrical Energy Systems has many years of experience in the research field. Numerous publications prove the necessary expertise. The investigations provide valuable results for the dedicated consideration of harmonics in the earth fault current, especially in the residual earth fault current at RESPE, and the description of the potential-raising effect of these on earthed equipment in different network constellations. On a scientific basis, quantitative criteria are provided for the evaluation of existing earthing measures and areal earthing systems.

与接地系统设计有关的中性点处理是电工系统和网络运行和规划中符合人身安全措施的重要组成部分。特别是对中高压电网的尺寸有影响。在发生接地故障电流和由此产生的接触电压时，必须遵守规范要求。在标称电压110kv及以下的电力系统中，主要的中性点处理是谐振中性点接地（RESPE）。这种中性点处理的优点是非常低的（残余）接地故障电流和在故障发生时相关的低接触电压。近年来的测量表明，高比例的谐波电流往往占接地故障剩余电流的主导地位。这导致了关于谐波电流对接地系统设计影响的争议性讨论。现行规范标准的测量方法总是参考均方根值，并与标称电网频率（50hz）有关。对高频分量的微分处理没有定义。考虑到这些，需要额外的措施，并导致预期的不允许的触摸电压。如果已知接地系统中随频率变化的电流分布，则可以忽略升电位电流的谐波分量。这大大减少了符合触摸电压所需的努力。在研究项目范围内，研究了接地系统中随频率变化的电流分布。基于对110kv及以下配电网的测量，建立了一个模型来描述局部分布的、频率相关的阻抗和发生接地故障时的有效电流回路。从根本上描述了大地和接地系统中随频率变化的电流分布。通过开发映射这种电流分布的数学程序，可以计算出地电流和地电压的减小系数。导出了配电网结构的最坏情况考虑。齐陶应用科学大学/Görlitz多年来一直在委员会的技术工作中发挥主导作用。电能系统主席在研究领域有多年的经验。许多出版物证明了必要的专业知识。这些研究结果为专门考虑接地故障电流中的谐波，特别是在RESPE的剩余接地故障电流中的谐波，以及描述这些谐波对不同网络星座接地设备的电位升高作用提供了有价值的结果。在科学的基础上，为现有接地措施和接地系统的评价提供了定量的标准。