EVS-EN 50526-2:2014

This European Standard applies to Voltage Limiting Devices (VLDs) to be applied in d.c. traction systems in order to comply with protective provisions against electric shock from d.c., and mixed a.c. – d.c. voltages, in accordance with the EN 50122 series, taking into account stray current provisions.
VLDs operate in such a way as to connect the track return circuit of d.c. railway systems to the earthing system or to conductive parts within the overhead contact line zone or current collector zone.