Software Design Of Short-Circuit Current Calculation Based On IEC60909 Standard

International Electrotechnical Commission(IEC) develop a new short-circuit current calculation standard of IEC60909(hereinafter referred to IEC standard) in 2001, which was formally approved to become the new national standard of engineering calculations in 2011. Compared with the traditional algorithm, the new algorithm has a greater degree of change. Currently, the foreign popular power system simulation software, such as EMTP, PSS/E, all have the function of short-circuit current calculation based on the IEC standard, while the domestic popular power system simulation software, such as BPA, PSASP, still lack of that feature. As the new national standard, IEC standard is practical, with a high reference value in network planning, design and operationThis paper first introduces the features and basic calculation method of the short-circuit current in AC system, focusing on comparing the differences between the proximal and the distal short-circuit current curves. Secondly, this paper make an in-depth research on the equivalent impedance calculation for each component in the AC system, and illustrate the practical significance, scientific evidence and specific methods of correcting impedance value. Correcting work of transformer and generator-transformer unit is the most complicated, and the presented optimization algorithm is just based on the transformer and generator- transformer unit model. The optimization algorithm allow to obtain the equivalent impedance in all cases by model-equivalent without modifying the admittance matrix. Based on this algorithm, it can realize quick short-circuit current scanning function. This paper also introduces calculating items of the IEC standard. Finally, on the basis of the above studies, combined with the current status of domestic and foreign short-circuit current calculation software, this paper developed a set of Fault Current Calculation Program which is compatible with BPA data format. It implements the function of short-circuit current rapid scanning based on IEC standard, and also implements the functions of SCR scanning and harmonic impedance scanning, which has been used for the actual system. Result based on an actual power system is presented to demonstrate the differences in accuracy and efficiency compared with other similar software, which shows the advantages of new software.