Dynamics analysis of 220 V DC auxiliary system in power plant using different mathematical models

The calculation of short-circuit currents in DC auxiliary systems of power plants and substations is essential for design and application of distribution and protective devices used in these systems. Because of differences between DC and AC auxiliary systems, DC system protection designers should be take into account that important fact in calculation and dimensioning of DC auxiliary system. There are several mathematical models that are usually used for calculation of short-circuit currents in DC auxiliary system. In this paper, the authors performed short-circuit currents calculation for one real DC auxiliary system of power plant using three different, well-known, mathematical models. The results of calculations were compared with results given by testing of selectivity of DC auxiliary system on the site. Based on comparison results of different calculations and testing on the site conclusion related to choice one of three the most often used mathematical models as the most suitable has deduced.