Electrical Safety and Stray Current Protection with Platform Screen Doors in DC Rapid Transit

Modern transit system are equipped with platform screen doors (PSDs) that represent a new element introduced in the electrical safety and stray current protection scenarios. Passengers may interact with PSDs and platform while boarding, leaving and waiting trains. Typical contractual requirements and applicable standards are discussed, identifying touch voltage scenarios suitably defining electrical circuits and parameters. DC voltage limits are at all clear and unambiguous in the range of relevant touch voltage values. The evaluation of exposure is thus carried out with the help of body impedance and body current models. Solutions are then discussed for protection of PSDs and passengers, including stray current limitation as constraint. A novel PSD bonding arrangement is proposed that reconciles insulation for utmost electrical safety level and bonding for traction fault protection.