A Novel Lifespan Approach for Assessment and Selection of Damping Systems Used in Hybrid DC Circuit Breakers Employed in Railways

Due to the constant growth and development of medium voltage DC (MVDC) grids in the current century, hybrid DC circuit breakers (DCCBs) are necessary to interrupt fault currents. The fast operation time of hybrid DCCBs and high speed at the moment of collision (opening/closing) can cause fatigue in mechanical disconnectors and other CB components. In this paper, a new algorithm based on the lifespan calculation of the equipment is implemented to evaluate system stress and select a suitable damping system. This approach provides clarity and simplicity when selecting damping systems and offers more detailed information on the reliability of the equipment. The modeling of this algorithm is established by the Finite Element Model (FEM) using COMSOL Multiphysics software. To validate this approach, an ultra-fast disconnector (UFD) of a 1.5 kV hybrid DCCB, intended for railways, is designed and fabricated, which can operate under 2 ms. Furthermore, the minimum mechanical endurance limit of the 1.5 kV DCCB is set at 10,000 or 20,000 operating cycles following the railway DCCB standard (IEC61992-2). Finally, mechanical and electrical dampers are selected by this algorithm, which uses the new lifespan approach in compliance with the IEC61992-2 standard.