When designing power supply systems, an important stage is the calculation of short-circuit currents, as well as parameters of other emergency modes. Based on the results of such calculations, the selection of electrical devices is carried out, including switches, disconnectors, limiters, measuring current and voltage transformers, as well as the settings of relay protection devices. In addition to the design of power supply systems, transient analysis is widely used in the study of the operating modes of electrical energy converters. In many cases, an analytical calculation allows you to obtain only approximate values, since a number of assumptions are made. Therefore, when designing power supply systems, an urgent task is to simulate transient processes in alternating current circuits using specialized software. This article discusses the features of modeling using programs such as MatLab Simulink and SimInTech - the Russian analogue of MatLab. Simulation and circuitry models of the transient process for currents flowing through the RLC load are constructed, and the results obtained using various software are compared. The simulation model was based on the basic equations, compiled according to the laws of electrical engineering, namely: I and II Kirchhoff's law, Ohm's law, the law of electromagnetic induction, the equation of displacement currents. The schematic model in the MatLab Simulink simulation environment is built using the SimScape library and standard electrical elements. The schematic model in the SimInTech modeling environment is built using the elements of the EC-Dynamics library. Comparison of the simulation results showed that the relative error of the results when calculating the electrical circuit by various methods in various simulation environments does not exceed 0.01%, which indicates a high simulation accuracy and the adequacy of each of the collected models.