The study of railway electromagnetic interference (EMI) seeks to determine the source of the interference or to ensure the correct operation of the equipment within adverse conditions. The complexity of railway system increases when more electronics are used. However a simple DC track circuit is still used in train detection systems in many countries, including Sweden, our case study. Most of the failures reported in the Swedish railway infrastructure are related to the detection system, making this research of interest to the railway community. By searching the Swedish failures report database, 0FELIA, for the most repetitive and probable causes of failures, they were identified three worst case scenarios: low resistance between the rails, external interference as a lightning and iron-powder-bridges in the insulated joint. They were simulated using the software CST STUDIO SUITE® (Computer Simulation Technology Studio Suite), supported by real measurements on site. Measurements followed the current EMC standards and were used to tune and validate the models, resulting in simulations very close to the real measures.