Numerical modeling in EMC problems of electric power substations when lightning strikes

For numerical modeling of lightning current spreading in lightning protection, grounding, electric power supply systems the ZYM program is used. Hybrid (field-circuit) thin-wire model is implemented in the program for electromagnetic fields and transients calculations (in ground and in air). Circuit model structure and its parameters are determined automatically, the user should only draw 3D model of a power substation and transmission line. The program is integrated with AutoCAD (using ObjectARX technology) that provides effective geometrical modeling with object and results visualization. Three impulse process calculation methods are researched and implemented: Fourier method, discrete circuits method (similar to ATP-EMTP) and step algorithm based on the Vlach method. The comparison of the methods shows the effectiveness of the latter. The wave process calculation caused by a lightning stroke in the overhead ground wire close to the power substation is carried out as an example. Surge voltage on the transformer and on the electrical equipment is determined before and after surge arrester is installed. The results are animated.