Earthing, Bonding, and Stray Current

This chapter discusses the concept of earthing and bonding (E&B) for the railway system (traction and auxiliary), including design provisions for stray current in direct current (DC) traction. The traction return system of the DC railway shall be completely insulated from all earthing installation, conductive structures, and soil. For alternating current railway systems, the return circuit is connected to the earthing system, e.g., via pole foundations and the structure earth of viaducts, tunnels and other structures. For this reason, a part of the traction return current flows via the earthing systems and the earth back to the traction substation. Protective E&B conductors shall be designed to withstand the maximum fault current under short‐term conditions according to the relevant tripping time of the backup protection. With respect to the earthing and equipotential bonding measures, it may be distinguished between indoor and outdoor equipment.