When new direct current (DC) powered rail transit systems are scheduled for construction effective electrical isolation from the earth is a key criterion. Electrical isolation is achieved through the use of insulating materials and regular maintenance resulting in nominal generation (leakage) of stray currents. Stray current leakage causes corrosion damage to rail transit system components and nearby buried metallic structures/pipelines.

Over time insulation materials break down due to environmental and operational factors including but not limited to the following; debris, organic matter (vegetation), and water intrusion. Ineffective insulation is a pathway for stray DC interference, reducing operational efficiency and possibly leading to an unsafe condition for equipment and personnel. Excessive levels of stray current leakage are likely to fuse metallic system components with arcing and may lead to fire.

The purpose of this paper is to discuss the inspection and maintenance methods necessary to sustain a safe and reliable DC powered rail transit system. The topics discussed are practical and the lessons learned are first-hand accounts taken from many years of construction and maintenance testing/troubleshooting.

Subject
Rail, Test methods, Materials, Leaks, Personnel, Equipment, Stray current, Health, safety, and environment, Construction, Electrical isolation, Maintenance, Visual assessment, Stray current corrosion
Keywords:
direct current, DC, light rail transit, stray current, interference, electrical isolation, testing, mitigation
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2025
Association for Materials Protection and Performance (AMPP)
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