The Approximate Method of Three Phase Short-Circuit Current Calculation Based on the Per-Unit Value Form of Ohm’s Law

Abstract

It is found that it is difficult to master the method to calculate the short circuit current by using the power unit system under the multi-grade voltages in the power system for the undergraduate students. This method is also important for the following courses studying and further practical working. Based on this purpose, the short circuit current is analyzed with the multi-grade voltages within the power system by using Ohm’s law in order to calculate the total impendence without voltage conversion. Firstly, the concepts about the rated average voltage and the per-unit system etc. are described in detail. Secondly the equation form about the per-unit value is described with the multi-grade voltages based on Ohm’s law, and including the simple calculation method of electrical elements impendence per-unit value. The results show that, applying the method proposed in the paper to the practical teaching, the students can easily master the content of the short-circuit current with multi-grade voltages within the power system by using per-unit system method.