The design and application of dc surge arresters to protect dc electrification system from transient overvoltage caused by lightning and switching surges is the purpose of this standard. Lightning surges can cause high energy transient overvoltages by direct or indirect coupling with a dc electrification system. Transient overvoltage protection from lightning and switching surges of various dc transit electrification systems can be achieved by the application of metal-oxide varistor (MOV) gapless-surge arresters. The application of surge arresters to running rails in areas where lightning activity is severe requires special study of protection coordination w...

This standard covers the application of dc surge arresters for transient overvoltage protection of dc transit electrification systems. These dc transit electrification systems include light rail, heavy rail, streetcar, and trolley bus systems. This standard covers the selection and application of metal-oxide varistor (MOV) gapless-surge arresters to divert surge energy away from the transit system components. It does not cover low-voltage SPDs that are required within dc traction power system equipment, such as rectifier units, vehicle propulsion systems, or other sensitive components of the dc transit system.

It is the purpose of this standard to provide uniform practices for lightning and switching transient overvoltage protection of dc transit electrification by proper selection of dc surge arresters based on the surge environment and site conditions of the transit system. This standard allows the use of SPDs in dc transit systems to avoid insulation failure due to transient overvoltage. Transient overvoltage protection is just as important as short- circuit protection. This standard will minimize equipment damage caused by transient overvoltages, increasing system reliability that will result in reduced maintenance.