Lightning, ground potential rise, and electrical damage; protecting wayside equipment on the MTA Long Island Rail Road

Abstract

Rail transportation systems are particularly prone to lightning and electrical damage. The many interconnected wayside systems are environmentally exposed and geographically distributed. Physical separation and the necessary interconnecting cables make the various signal, communications and power systems prime targets for damage from ground potential differences. The MTA Long Island Rail Road (LIRR) provides an excellent case study for this subject. As the largest commuter railroad in the US, the LIRR has a very high density of electrical and electronic equipment located along its right-of-way. Although the incidence of lightning on Long Island is relatively moderate, earth ground disturbances are of a much higher magnitude, due to extremely poor soil conductivity. To address these issues, the LIRR Engineering Department formed a multi-disciplinary task force. Their investigations revealed that equipment damage had been incorrectly attributed to either lightning or DC traction power faults. Investigations showed the main cause was actually AC transmission and distribution line power faults, due to a lack of inductive coordination. This paper provides some background information on lightning, power faults, and ground potential differences, and summarizes the Railroad's experience since it began seriously addressing these problems seven years ago.