CLC/SR 73 - Short-circuit currents

IEC 60909-0:2016 is applicable to the calculation of short-circuit currents in low-voltage three-phase AC systems, and in high-voltage three-phase AC systems, operating at a nominal frequency of 50 Hz or 60 Hz. It establishes a general, practicable and concise procedure leading to results which are generally of acceptable accuracy and deals with the calculation of short-circuit currents in the case of balanced or unbalanced short circuits. This second edition cancels and replaces the first edition published in 2001. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - contribution of windpower station units to the short-circuit current; - contribution of power station units with ful size converters to the short-circuit current; - new document structure.

IEC 60865-1:2011 is applicable to the mechanical and thermal effects of short-circuit currents. It contains procedures for the calculation of: the electromagnetic effect on rigid conductors and flexible conductors, the thermal effect on bare conductors. For cables and insulated conductors, reference is made, for example, to IEC 60949 and IEC 60986. For the electromagnetic and thermal effects in d.c. auxiliary installations of power plants and substations reference is made to IEC 61660-2. Only a.c. systems are dealt with in this standard. This third edition cancels and replaces the second edition published in 1993 and constitutes a technical revision. The main changes with respect to the previous edition are: - The determinations for automatic reclosure together with rigid conductors have been revised. - The influence of mid-span droppers to the span has been included. For vertical cable-connection the displacement and the tensile force onto the lower fixing point may now be calculated. Additional recommendations for foundation loads due to tensile forces have been added. The subclause for determination of the thermal equivalent short-circuits current has been deleted (it is now part of IEC 60909-0). The regulations for thermal effects of electrical equipment have been deleted. The standard has been reorganized and some of the symbols have been changed to follow the conceptual characteristic of international standards.

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 IE C 60909-0:2001. NEW! 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.

Describes a method for calculation of the mechanical and thermal effects on rigid conductors caused by short-circuit currents in d.c. auxilliary installations in power plants and substations, as described in EN 61660-1. Provides a method which has wide application and which gives results of sufficient accuracy. The calculation method is based on substitute functions, which cause approximately the same maximum stresses in the conductors and the same forces on the supports as the actual electromagnetic force.

Describes method for calculating short-circuit currents in d.c. auxilliary systems in power plants and substations, which can be equipped with the following equipment, acting as short-circuit current sources: - rectifiers in three-phase a.c. bridge connection for 50 Hz; - stationary lead-acid batteries; - smoothing capacitors; - d.c. motors with independent excitation Provides a generally applicable method of calculation which produces results of sufficient accuracy on the conservative side.

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.

This application guide presents a practical method to be used when calculating short-circuit currents in low-voltage networks. The method corresponds strictly with HD 533 and leads to conservative results with sufficient accuracy. Two short-circuit currents which differ in magnitude are to be calculated: -the maximum short-circuit current which causes the maximum thermal and electromagnetic effects on electrical equipment and determines the required capacity or rating; -the minimum short-circuit current which may be a basis for the adjustment of protective devices.

Applicable to the calculation of short-circuit currents: - in low-voltage three-phase a.c. systems - in high-voltage three-phase a.c. systems operating at a nominal frequency of 50 Hz or 60 Hz. Systems at highest voltages of 550 kV and above with long transmission lines need special consideration. The contents of the corrigendum of February 2002 have been included in this copy.

Contains standardized procedures for the calculation of the effects of short-circuit currents in two sections as follows: - the electromagnetic effect on rigid conductors and flexible conductors; the thermal effect on bare conductors. Only a.c. systems for rated voltages up to and including 420 kV are dealt with.

This standard is applicable to the calculation of short-circuit currents: -in low-voltage three-phase a.c. systems, -in high-voltage three-phase a.c. systems with nominal voltages up to 230 kV operating at nominal frequency (50 Hz or 60 Hz). This standardized procedure is given in such a form as to facilitate as far as possible its use by non-specialist engineers.