Scientific paper ID 2751 : 2025/3

The commissioning of some of the oldest metro stations and the corresponding traction lowering stations (TPS) in ”Metropolitan” - Sofia (”Konstantin Velichkov”, ”Vardar”, ”Zapaden Park”, ”Lyulin”) took place on 28.01.1998. In each of these TPS, standardized and uniform equipment and systems are used, which are supplied with an input AC voltage of 10 kV from several independent sources. The function for which these facilities are intended is mainly to ensure and provide reliable power supply from the contact rail (CR) of the respective section for movement with a constant voltage of 850V, as well as to ensure the necessary power supply for all other consumers of the given metro station (lighting, escalators, elevators, emergency lighting, etc.). The security of the power supply of the contact rail, the safe movement of trains and the safe and secure transportation of passengers are the most important tasks for the implementation of underground transport in the city of Sofia.

Management of all facilities in each TPS, the collection of data on events occurring during the normal operation of the traction substation and complex dynamic processes, is carried out through a dispatching system for control and data collection SCADA. Through it, control is implemented and the status of all main facilities is monitored, by transmitting information to the Dispatching Center. The report examines some of the most frequently occurring failures and defects in the process of normal operation (normal operating mode) in the TPS in Metropolitan-Sofia. Specific problem areas, failures and units that occurred, as well as the consequences of these failures and defects are indicated.