Sector applications · Complies to RDSO
Railway and Metro Earthing and Protection
Railways and metros combine traction power, signalling and public areas along one corridor. Protection manages earthing and bonding of the traction return, limits touch voltages on platforms and structures, and protects signalling and telecom equipment from lightning and traction surges.
When it applies
- Mainline AC electrified railways
- DC metro and light-rail systems
- Stations, depots and traction substations
- Signalling, telecom and electronic interlocking installations
When it does not
- Traction power design itself, which belongs to the railway's system designer
- Rolling stock
- Any work that departs from the railway administration's approved specifications
How the system works
- AssessA lightning risk assessment and the sector's own standard set the protection level.
- Earth and bondEvery structure, frame and cabinet is joined to one earthing system.
- Protect the linesCoordinated surge protective devices are fitted on power, DC, RF and data lines.
- Monitor and maintainCounters and status contacts show what happened; inspection keeps the system in service.
Coordinated surge protection
Each device takes its share. The Class I device diverts lightning current at the service entry; Class II and III devices bring the remaining voltage below what the equipment can withstand.
Design parameters
The values a consultant or contractor needs to fix before the system is drawn.
| Parameter | Typical value or rule | Reference |
|---|---|---|
| Earthing and return circuit | Protective provisions against electric shock on AC and DC traction systems | EN 50122-1 |
| Stray current | DC systems: return circuit insulated from earth; stray-current monitoring | EN 50122-2 |
| Signalling and telecom earthing | Low-resistance, maintenance-free earth with ring conductor; values per the RDSO specification, typically 1 Ω or lower | RDSO specifications |
| Surge protection | Coordinated SPDs on power, signalling and data lines of interlocking and telecom rooms | IEC 61643-11 · IEC 61643-21 |
| Station structures | Platform roofs and foot-over-bridges protected and bonded | IEC 62305-3 |
| Maintenance earthing | Portable earthing for overhead line and substation work | IEC 61230 |
Solution pack: component BOQ
Each line opens the LPES product category. Part codes and final quantities are confirmed on your quote from the drawings.
| Component | Role in the system | Quantity rule |
|---|---|---|
| Earthing Conductors | Earthing and bonding conductors for structures, rooms and equipment | Route length from the bonding plan |
| Portable & Temporary Earthing | Portable earthing sets for overhead line and substation maintenance | One set per maintenance gang per voltage |
| Type 1 Lightning-current Arresters | Surge protection at power incomers of signalling and telecom rooms | One set per incomer |
| Earth Pits, Chambers & Covers | Inspection chambers for electrodes along the corridor | One per electrode |
From design to handover
- Collect the administration's specifications and the earthing and bonding plan
- Design earthing for stations, signalling rooms and substations
- Install electrodes, ring conductors and bonding
- Fit coordinated surge protection on power, signalling and data lines
- Test, document and submit for the administration's acceptance
Services for this solution
Industries that use it
What the standards require
Checked against the current editions held in the LPES standards library.
- IEC 62305-2:2024
- Risk to life and physical damage is compared with a tolerable risk of 10⁻⁵ per year; failure of internal systems is judged separately as a frequency.
- IEC 62305-4:2024
- A coordinated SPD system protects against conducted surges only. Radiated fields need shielding and cable routing.
- IEC 62305-4:2024 Cl. 7
- Where an external LPS exists, a Class I (Type 1) SPD is required at the service entry.
- IEC 62305-4:2024
- Earthing conductor to the SPD: 16 mm² copper for Class I, 6 mm² for Class II and 1.5 mm² for Class III.
- CEA Safety Regulations 2023, Reg. 38(3)
- Lightning protection is addressed for multi-storeyed buildings above 15 m and listed public premises such as airports, hospitals and hotels.
- IEEE 80-2013
- A substation grid is judged by touch and step voltage against the tolerable limits, not by its resistance alone.
Regulation and standards cross-check
What Indian regulation and the wider standards add to this solution. Paraphrased; confirm against the current official text, amendments and state notifications before relying on a clause in a tender or inspection.
| Standard | Clause | What it requires |
|---|---|---|
| IEC 61936-1:2021 | Clause 1 | Railway power-supply substations are within scope. Electrified railway tracks and rolling stock are excluded and follow the traction standards. |
| CEA Safety Regulations 2023 | Reg 38(3)(vi) | Lightning protection is required for multi-storeyed buildings above 15 m and for listed premises, which include hospitals, hotels, academic buildings, industrial installations and other public buildings. The regulation names no design standard, so IS/IEC 62305 applies through Reg 14. |
| CEA Safety Regulations 2023 | Reg 50 | Above 650 V the whole switchyard or substation, including non-current-carrying metal, is connected to an earthing system or mat that limits touch and step potential and earth potential rise, including potential transferred through earth wires, cable sheaths, fences and pipelines. |
| CEA Safety Regulations 2023 | Reg 77 | Owners of overhead lines, substations and generating stations exposed to lightning must divert lightning surges to earth. The arrester earthing lead is kept as short and straight as possible, does not pass through steel pipe, and goes to a separate vertical electrode or to a junction of the earth mat. |
| IEC 61936-1:2021 | 10.2.3, Table 6 | High-voltage and low-voltage earthing are interconnected where practicable. Where low-voltage circuits leave the high-voltage earthing area, earth potential rise is held to 1,200 V for faults cleared within 5 s and 250 V beyond 5 s, unless a global earthing system exists. |
| IEEE Std 80-2013 | Clause 17 | Special areas are checked one by one: the fence, with a perimeter conductor about 1 m outside it or bonding, operating-handle mats, cable sheaths, surge arrester earthing, and potentials transferred by communication circuits, pipes, rails and low-voltage neutrals. |
| CEA Safety Regulations 2023 | Reg 14(2), Reg 2(1)(zze) | Relevant standards, including the National Electrical Code and the National Building Code, shall be followed. Indian Standards come first, then IEC, IEEE and European Norms in that order. Where a standard and the regulations differ, the regulations prevail. |
What we ask for before design starts
- Single-line diagram with sources, operating modes and earthing arrangement
- Equipment list with impulse withstand levels
- Cable routes and every point where services enter
- Fault levels and protection clearing times
- Existing earthing and lightning protection records
- Site layout with fences, pipes, rails and neighbouring installations
Try the numbers
Protection level explorer
- Rolling-sphere radius
- 45 m
- Mesh size
- 15 × 15 m
- Down-conductor spacing
- 15 m
- Peak current covered
- 100 kA
- Coefficient ki
- 0.04
- Interception efficiency
- 90%
Values from IEC 62305-1 and IEC 62305-3. The level for your structure comes from the risk assessment.
Tolerable touch and step voltage
- Tolerable touch voltage
- –
- Tolerable step voltage
- –
- Surface derating Cs
- –
IEEE Std 80-2013, equations 27 and 29 to 33. Set the thickness to 0 for no crushed-rock layer. These are limits; the grid design must keep mesh and step voltage below them.
What we find on audits
- Equipment earths and lightning earths kept separate
- Surge protective devices chosen without coordination or the right voltage rating
- Long connecting leads that add kilovolts to the protection level
- Data and signal lines left unprotected while power lines are protected
- No inspection after a strike, so failed devices stay in service
What you receive: the LPES Protection Passport
- As-built drawings of the installed system
- Risk assessment and design calculations
- Test results: earth resistance, continuity, SPD checks
- Component list with part codes and type-test references
- Inspection schedule for the protection level
Lightning to Load: one accountable partner
- Assess
- Design
- Specify
- Supply
- Implement
- Verify
- Assure
Standards basis
IEC 62305-2, -3 and -4:2024 (Ed. 3) · IEC 61643 series · IEEE 80-2013 · IEC 61936-1:2021 · IS 3043:2026 · CEA Safety Regulations 2023 · IS 732:2019 · IEC 60364-6:2016 · IEC 61936-1:2021
Reviewed by LPES engineering, November 2026. Clause and table numbers follow IEC 62305:2024 (Edition 3) and IS 3043:2026.
Questions engineers ask
What earth resistance do signalling installations need?
RDSO specifications set the value; 1 Ω or lower is typical for electronic interlocking. The current specification governs. Compliance Audit
Why is DC metro earthing different?
DC return current that leaks into the ground corrodes buried metal, so the return circuit is insulated from earth and stray current is monitored. Earthing System Design
How are signalling rooms protected from surges?
With coordinated SPDs on the power supply and on every signalling and data line entering the room. Type 1 Lightning-current Arresters
What is portable earthing used for?
To earth and short-circuit the overhead line or equipment before work, so that it cannot become live. Portable & Temporary Earthing
Which conductors are used for bonding?
Copper or galvanised steel conductors sized for the fault current, as shown on the bonding plan. Earthing Conductors
Get this solution quoted for your site
Send the drawings or the basic dimensions. LPES returns the design parameters, the BOQ with part codes and the price in one offer.
