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

Modern transit systems are equipped with platform screen doors (PSDs) that represent a new element introduced in electrical safety and stray current protection scenarios. Passengers may interact with PSDs and platforms while boarding, leaving, and waiting for trains. Typical contractual requirements and applicable standards are discussed, identifying touch voltage scenarios suitably defining electrical circuits and parameters. The 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 the protection of PSDs and passengers, including stray current limitations as a constraint. A novel PSD bonding arrangement is proposed, which reconciles insulation for utmost electrical safety level and bonding for traction fault protection.