三相交流系统中的短路电流 第3部分：两个单独的同时线路对地短路期间的电流和流经大地的部分短路电流

[中文适用范围]： IEC 60909-3:2009 RLV 包含国际标准及其红线版本。 Redline 版本为您提供了一种快速、简单的方法来比较该标准与其先前版本之间的所有更改。 Redline 版本不是正式的 IEC 标准，只有当前版本的标准才被视为正式文件。 IEC 60909-3:2009 规定了在标称频率 50 Hz 或 60 Hz 下运行的高压三相交流系统中不平衡短路情况下预期短路电流的计算程序，即： - 两条单独的同时线路中的电流- 隔离中性点或谐振接地中性点系统中的对地短路； - 在直接接地或低阻抗接地中性系统中单线对地短路的情况下流经大地的部分短路电流。通过这些程序计算出的电流用于确定车站（发电站或变电站）和架空线路塔的感应电压或接触电压或跨步电压以及地电位升高。给出了计算具有一根或两根地线的架空线路折减系数的程序。此版本构成技术修订。相对于前一版本的主要变化是： - 引入了新的程序，用于计算护套或屏蔽层的折减系数，此外还引入了通过三芯电缆或三个单芯电缆的接地和护套或屏蔽层的电流分布。两端接地的金属非磁性护套或屏蔽芯线； ——修正了带地线架空线路折减系数的计算信息，并在新的第7章中给出； ——增加了第8章，用于计算两端金属护套或屏蔽层接地的三芯电缆的电流分布和折减系数； - 新的附录C和D提供了在两端带有金属护套和屏蔽层的电缆的情况下计算折减系数和电流分布的示例。 [外文原描述]： IEC 60909-3:2009 RLV contains the International Standard and its Redline version. The Redline version provides you with a quick and easy way to compare all the changes between this standard and its previous edition. The Redline version is not an official IEC Standard, only the current version of the standard is to be considered the official document. IEC 60909-3:2009 specifies procedures for calculation of the prospective short-circuit currents with an unbalanced short circuit in high-voltage three-phase a.c. systems operating at nominal frequency 50 Hz or 60 Hz, i. e.: - currents during two separate simultaneous line-to-earth short circuits in isolated neutral or resonant earthed neutral systems; - partial short-circuit currents flowing through earth in case of single line-to-earth short circuit in solidly earthed or low-impedance earthed neutral systems. The currents calculated by these procedures are used when determining induced voltages or touch or step voltages and rise of earth potential at a station (power station or substation) and the towers of overhead lines. Procedures are given for the calculation of reduction factors of overhead lines with one or two earth wires. This edition constitutes a technical revision. The main changes with respect to the previous edition are: - New procedures are introduced for the calculation of reduction factors of the sheaths or shields and in addition the current distribution through earth and the sheaths or shields of three-core cables or of three single-core cables with metallic non-magnetic sheaths or shields earthed at both ends; - The information for the calculation of the reduction factor of overhead lines with earth wires are corrected and given in the new Clause 7; - A new Clause 8 is introduced for the calculation of current distribution and reduction factor of three-core cables with metallic sheath or shield earthed at both ends; - The new Annexes C and D provide examples for the calculation of reduction factors and current distribution in case of cables with metallic sheath and shield earthed at both ends.