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IEC 国际电工标准国际

IEC 60909-1 Short-circuit currents in three phase

三相交流系统中的短路电流 – 第1部分：根据IEC 60909-0计算短路电流的系数

IEC 60909-1 Short-circuit currents in three phase a.c. systems-1 Factors for the calculation of short-circuit currents according to IEC 60909

Short-circuit currents in three-phase AC systems – Part 1: Factors for the calculation of short-circuit currents according to IEC 60909-0

版本年份 2002 文件语言 英语 全文 6 页 格式 PDF
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IEC 60909-1 Short-circuit currents in three phase 三相交流系统中的短路电流 – 第1部分：根据IEC 60909-0计算短路电流的系数封面

标准信息

STANDARD INFORMATION
标准编号
IEC 60909-1 Short-circuit currents in three phase
所属分类
IEC 国际电工标准
发布机构
IEC
版本年份
2002
文件语言
英语
文件格式
PDF
文件页数
6 页
文件大小
6.78 MB

中文名称为参考译名，文件语言以原文为准。

· 更新：

标准简介

OVERVIEW

中文简介

该标准是IEC 60909系列的技术报告，旨在解释用于计算三相交流系统短路电流的各种系数的来源和应用。它作为IEC 60909-0的补充，详细说明了电压系数、发电机和变压器系数等在标准化计算程序中的具体使用方法，以满足技术精度和简单性的要求。

English summary

This technical report is part of the IEC 60909 series, aiming to explain the origin and application of factors used for calculating short-circuit currents in three-phase AC systems. It serves as an addition to IEC 60909-0, detailing the specific usage of voltage, generator, and transformer factors within the standardized calculation procedure to meet requirements for technical precision and simplicity.

以上为根据文件整理的内容简介。

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IEC 60909-1 Short-circuit currents in three phasePDF 第 1 页 · 原页码 1

1.4.2 Subscripts

0No load (T0)
aApproximation
adAdmissible
dDirect axis
eExact
fField of the synchronous machine
IECaccording to IEC 60909-0, for example KS(IEC)
iInternal
LLoad
MAXMaximum (short-circuit current at worst-case load flow)
NNetwork
qQuadrature axis
SSuperposition method
*Per unit quantity

1.4.3 Superscripts

bBefore
'Transient
"Subtransient

2 Factors used in IEC 60909-0

2.1 Voltage factor c for the equivalent voltage source at the short-circuit location

2.1.1 General

The magnitude of a short-circuit current in a three-phase a.c. system (maximum or minimum short-circuit current) at any location depends primarily on the network configuration, the generators or power-station units and the motors in operation and secondarily on the operational stage of the network before the short circuit.

The variations during operation in a three-phase a.c. system are very large. Therefore, it is difficult to find the special load flow that leads either to a maximum or to a minimum short-circuit current at the different locations of the network. In a given system, there are as many different short-circuit current magnitudes as there are possible different load-flow conditions for every location. Normally, extreme load-flow cases are not empirically known.

IEC 60909-0 therefore recommends a calculation method with the equivalent voltage source cUn/√3 at the short-circuit location. This method, described in IEC 60909-0, is an approximation method without special conditions of operation. The aim of this standard is to find the maximum short-circuit currents with sufficient accuracy, mainly taking into account safety aspects and as far as possible economical aspects.

During the planning stage of a network, the different future load-flow conditions are unknown. Therefore, the equivalent voltage source cUn/√3 is based on the nominal system voltage Un and the voltage factor c = cmax or c = cmin for the calculation of the maximum or the minimum short-circuit currents. These factors c are given in table 1 of IEC 60909-0. The introduction of a voltage factor c is necessary for various reasons (IEC 60909-0, 1.3.15). These are:

  • voltage variation depending on time and place;
  • changing of transformer taps;
  • neglecting loads and capacitances by calculating according to IEC 60909-0 (see 2.3.1);
  • the subtransient behaviour of generators, power-station units and motors.

The meaning of the voltage factor c is illustrated for a simple model of a radial network in 2.1.4. Furthermore, results of extended calculations given in 2.2.5 and 2.3.4 demonstrate the possible deviations of calculations with the equivalent voltage source at the short-circuit location against the worst-case values found with a special procedure using the superposition method.

2.1.2 Calculation methods

In principle, there are two methods for the calculation of the initial symmetrical short-circuit current at the short-circuit location (IEC 60909-0, figures 1 and 2):

  • the superposition method, derived from Helmholtz's or Thevenin's principle;
  • the method using the equivalent voltage source at the short-circuit location (see 2.1.3).

Examples for the superposition method are given in 2.2 and 2.3. There the results of the superposition method are compared with the results found with the method using the equivalent voltage source at the short-circuit location.

If a certain load flow in an existing network is known, then it is possible to calculate the initial symmetrical short-circuit current with the superposition method, but this method gives the short-circuit current only related to the load flow presupposed. Therefore, it does not necessarily lead to the maximum short-circuit current. The reason is that for one short-circuit location there are as many short-circuit currents as load-flow conditions without exceeding the boundary conditions of voltages and currents during normal operation, even if the same operational voltage at the short-circuit location is given.

To overcome this problem and to find the worst-case load flow that leads to the maximum short-circuit current at one short-circuit location, a special method was developed by varying the operation conditions [9], [13], [26]1). Further information is given in 2.2.5 and 2.3.4.

2.1.3 Equivalent voltage source at the short-circuit location and voltage factor c

The procedure for the calculation of the initial symmetrical short-circuit current using the equivalent voltage source at the short-circuit location is described in IEC 60909-0. This method, which is normally based only on the rated data of electrical equipment, is an essential simplification compared to the superposition method or a transient calculation, because also in this case it is necessary to know the load-flow conditions before the short circuit.

Using this simplified procedure, the equivalent voltage source cUn/√3 at the short-circuit location is the only active voltage in the positive-sequence system. All network feeders, synchronous machines and asynchronous motors are short-circuited behind their internal (subtransient) reactances (IEC 60909-0, 3.6.1). All the shunt capacitances and the shunt admittances (loads), except those of the motors, are to be omitted in the positive- and the negative-sequence system (IEC 60909-0, 2.3). Capacitances of the zero-sequence system are to be considered in general. The zero-sequence capacitances are to be omitted in low-voltage systems and in high-voltage effectively grounded systems (i.e. earth fault factor δ ≤ 1,4). Special considerations are necessary in high-voltage networks with long-distance lines and, of course, in the case of isolated neutral or resonant earthed networks (IEC 60909-0, 1.1). An example for the application of the calculation using the equivalent voltage source at the short-circuit location F is given in IEC 60909-0, figure 4.

1) The figures in square brackets refer to the bibliography.

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