标准摘要
[中文适用范围]： IEC 60909 的这一部分规定了在标称频率 50 Hz 或 60 Hz@ iea) 下运行的高压三相交流系统中，在两个单独的同时线对电流期间，计算不平衡短路情况下的预期短路电流的程序。 - 中性点隔离或谐振接地系统中的对地短路；b) 直接接地或低阻抗接地中性系统中单线对地短路情况下流经大地的部分短路电流。当确定车站（发电厂或变电站）的感应电压或接触电压或跨步电压以及接地电位升高时，使用程序。本标准不包括：a）在短路测试中的受控条件下故意产生的短路电流站@ orb) 船舶或飞机上电气装置的短路电流@ orc) 隔离或谐振接地系统中的单线对地故障。本标准的目的是建立实用且简明的计算程序两个单独同时发生的线对地短路期间的线对地短路电流以及电气装置@通过地球的部分短路电流，导致具有足够精度的保守结果。为此，通过考虑在短路位置施加的等效电压源并将所有其他源设置为零来确定电流。该程序适用于手动方法或数字计算测定。本标准是对IEC 60909-0的补充。一般定义@符号和计算假设参考该出版物。本文件仅定义或指定特殊项目。这并不排除使用特殊方法@例如根据特定情况调整的叠加方法@如果它们至少给出相同的精度。如IEC 60909-0中所述@短路电流及其参数也可以通过以下方式确定根据电气设备的额定数据和系统的拓扑布置计算短路参数的优点是既可以用于现有系统，也可以用于规划阶段的系统。 [外文原描述]： IEC 60909-3:2009 is also available as IEC Standards+ 60909-3:2009 which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition. 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. This publication is to be read in conjunction with IEC 60909-0:2001.
英文名称Short-circuit currents in three-phase AC systems - Part 3: Currents during two separate simultaneous line-to-earth short circuits and partial short-circuit currents flowing through earth