GB/T 15544.1-2023 Short-circuit current calculation in three-phase a.c. systems—Part 1:Calculation of currents

Scope

This document specifies the calculation method for short-circuit current in three-phase AC systems with a rated frequency of 50 Hz. The equivalent voltage source method at the short-circuit point proposed in this document is a simple and practical method for calculating short-circuit current, and the calculation results generally have acceptable accuracy. If the same calculation accuracy can be achieved, other calculation methods, such as the superposition method, are not excluded. The short-circuit current calculated by the superposition method depends on a specific power flow, so it may not be the maximum short-circuit current. This document is applicable to the calculation of short-circuit current for balanced short-circuit faults and unbalanced short-circuit faults. It is not applicable to the calculation of short-circuit current for a single-phase grounding fault in a neutral-point ungrounded or resonant-grounded system. It is not applicable to the calculation of short-circuit current for artificial short-circuits under controlled conditions (short-circuit test stations) or for electrical equipment on aircraft and ships. For two independent single-phase grounding short-circuit faults occurring simultaneously in a neutral-point ungrounded or resonant-grounded system, the calculation of short-circuit current is described in GB/T 15544.4-2017. Short-circuit current and short-circuit impedance can also be determined through system tests, measurements by system analysis instruments, or digital computers. In existing low-voltage systems, short-circuit impedance can be measured at the expected short-circuit point. The calculation of short-circuit impedance is typically based on the rated parameters of power equipment and the topology of the system. The advantage of this method is that it can be applied to both existing and planned systems. Generally, two different amplitudes of short-circuit current need to be calculated: -- the maximum short-circuit current, used to

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