The method of "characteristic" currents and countercurrents for short-circuits diagnosis

Many softwares are available to analyze the design of electrical power systems. Therefore, it becomes relevant to know rules of thumb to be able to diagnose in an elementary and intuitive way the computerized results. For the short circuit analysis, in most practical cases, it is sufficient to adopt simplified and standard based calculation methods. The paper introduces the parameter of the countercurrents and illustrates the approach of the short-circuit models of power system components based on the "characteristic" currents method CCM. The paper, at first, presents a short overview of the IEC Std 60909, assumed as reference for the proposed approach.