Railway traction earthing protects people and equipment while managing the return current that flows through the rails and earth. On DC traction especially, part of that current strays into the ground as stray current and corrodes buried pipes and structures - so the earthing and bonding are designed to control it, not just to clear faults.
Traction earthing
- 25 kV AC traction - OHE mast and structure earthing, booster and return conductors.
- DC metro traction - carefully controlled return path to limit stray current.
- Substation and signalling earths kept separate then bonded.
- Track and structure bonding to equalise potential.
Stray-current corrosion
Stray current leaves the rail, passes through buried metal and returns, corroding that metal where it leaves. Control it with a low-resistance, insulated return path, drainage bonds, and monitoring - alongside corrosion-resistant copper earthing. See the railway and metro earthing guide.
