Abstract
The article analyzes short circuit current reduction due to three main factors: electrical arc, cable heating and contact and coil resistance in auxiliary network of traction substations. The research was made using ETAP software module Unbalance Short Circuit, where mathematical model of dynamic arc, as it is described by Russian and abroad scientists, iterative cable heating as it is described in Russian and European standards and contact resistance were implemented. Mathematical model includes power grid, auxiliary transformer, circuit breakers, current transformer, and cable. Cable size varies to show influence of each above-mentioned factors. Calculations were made using phase domain method and all the parts of auxiliary network were considered. The results show up to 60 percent decrease in three-phase short circuit current considering three factors together. It influences the ability to trip short circuit current by backup protections, fault-clearing time, cable sizing and the power supply quality. Neglect of one or more factors may, in some cases, mean insensitivity of the protection and the inability to trip the short circuit current in time.
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