IEEE Draft Standard for Grounding Practices for dc Electrification Overhead Contact Systems, Including Application of Lightning Arresters, for Transit Systems

This standard is a basis for the design and application of dc surge protection devices to assist in protecting Overhead Contact System (OCS) from transient overvoltages associated with lightning and switching surges. Switching surges are inherent characteristics of electrification system and are generally considered low energy transient overvoltages. Lightning surges are natural, caused by electrical discharge that occurs in the atmosphere between clouds or between clouds and ground. Lightning surges are known for causing very high energy transient overvoltages by direct or indirect coupling with OCS. This standard covers transient overvoltage protection of OCS used in dc transit rail electrification systems. Transient overvoltage protection of third rail dc and the running rails may be achieved by the application of same type of surge protection devices as are recommended for the OCS, although these rails are generally less likely to be affected by lightning transient overvoltages due to their proximity to earth where flash-over can occur to drain surge energy away from the rails without the application of surge overvoltage protection devices. The word surge arrester instead of lightning arrester has been used in this standard without affecting the technical contents of the standard.