Insulated joint for corrosion protection of buried subway gallery structure: consideration on cable ground connection

Protection against corrosion of a subway´s metallic structure can be performed by insulated joints at the interface between galleries and stations. A preliminary analysis shows some differences in stray current flowing and a possible improvement of protection depending on the joint region configuration. This analysis is performed by means of a commercial three-dimensional finite-element method. A consequence of using insulated joints is a suitable grounding of the sheaths belonging to power and signal cables laying inside the gallery and particular care in connecting them to ground electrical masses or other metallic structures in order to avoid shunting insulated joints. Induced voltages and currents must be predicted to avoid any danger in both under-rated and fault conditions.