IS/IEC 62305:2010 Part 3 is the Indian Standard (BIS) for protection against lightning - part 3: physical damage to structures and life hazard. This standard provides requirements for the protection of structures against physical damage by means of a lightning protection system (LPS), and for protection of life against injury from touch and step voltages. It details the design, installation, and maintenance of external LPS components like air-termination systems, down-conductors, and earth-termination systems based on a risk-assessed Lightning Protection Level (LPL).
Specifies requirements for protection measures against physical damage to structures and danger to life within the structure caused by lightning flashes.
Quick Reference — Top IS/IEC 62305 Part 3:2010 Values
Key parameters for LPS design: rolling sphere radii, mesh sizes, conductor spacing, material dimensions, and separation distance factors.
| Reference | Value | Clause |
|---|
| Rolling Sphere Radius (LPL I) | 20 m | Cl. 5.2.2 (Table 2) |
| Rolling Sphere Radius (LPL II) | 30 m | Cl. 5.2.2 (Table 2) |
| Rolling Sphere Radius (LPL III) | 45 m | Cl. 5.2.2 (Table 2) |
| Rolling Sphere Radius (LPL IV) | 60 m | Cl. 5.2.2 (Table 2) |
| Max. Mesh Size (LPL I) | 5 m x 5 m | Cl. 5.2.3 (Table 2) |
| Max. Mesh Size (LPL IV) | 20 m x 20 m | Cl. 5.2.3 (Table 2) |
| Typical Down-conductor Spacing (LPL I) | 10 m | Cl. 5.3.3 (Table 3) |
| Typical Down-conductor Spacing (LPL IV) | 20 m | Cl. 5.3.3 (Table 3) |
| Min. Length, Vertical Earth Electrode (LPL I)— For Type A arrangement, low resistivity soil. l₁ in Fig. 3. | 5 m | Cl. 5.4.2.2 (Table 4) |
| Min. Length, Horizontal Earth Electrode (LPL I)— For Type A arrangement, low resistivity soil. l₁ in Fig. 3. | 5 m | Cl. 5.4.2.2 (Table 4) |
| Min. Radius of Ring Earth Electrode (Type B)— Equivalent radius of the area enclosed by the ring electrode. | 5 m | Cl. 5.4.2.3 |
| Min. Cross-section, Copper Air-termination Tape— Minimum thickness 2 mm. | 50 mm² | Cl. 5.6.2 (Table 6) |
| Min. Diameter, Solid Copper Air-termination Rod— Cross-section 50 mm². | 8 mm | Cl. 5.6.2 (Table 6) |
| Min. Cross-section, Hot-dip Galv. Steel Tape— Minimum thickness 2.5 mm. | 50 mm² | Cl. 5.6.2 (Table 6) |
| Min. Diameter, Solid Copper Earth Electrode Rod | 14 mm | Cl. 5.6.2 (Table 7) |
| Min. Diameter, Hot-dip Galv. Steel Earth Electrode Rod | 16 mm | Cl. 5.6.2 (Table 7) |
| Separation Distance Factor `ki` (LPL I) | 0.08 | Cl. 6.3 (Table 10) |
| Separation Distance Factor `ki` (LPL III) | 0.04 | Cl. 6.3 (Table 10) |
| Separation Distance Factor `kc` (2 down-conductors)— For non-interconnected ring conductors. | 0.66 | Cl. 6.3 (Table 9) |
| Separation Distance Factor `km` (Air)— Material providing electrical insulation. | 1 | Cl. 6.3 (Table 11) |
| Min. Thickness of Metal Sheet (Steel) as Air-termination— To prevent puncture or hot-spot problems. | 4 mm | Annex C (Table C.1) |
| Min. Thickness of Metal Sheet (Copper) as Air-termination— To prevent puncture or hot-spot problems. | 5 mm | Annex C (Table C.1) |
⚠ Verify against the latest BIS/IEC publication and project specifications. Amendment Slips may modify values.
Overview
- Status
- Current
- Usage level
- Essential
- Domain
- MEP — Electrical Installations
- Type
- Code of Practice
Also on InfraLens for IS/IEC 62305
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! The selection of the Lightning Protection Level (LPL) is not arbitrary; it must be determined using the detailed risk assessment methodology in IS/IEC 62305-2.
! Proper earthing is the most critical and often weakest link in an LPS. Achieving and maintaining low earth resistance (<10Ω) is paramount for effective dissipation of lightning current.
! Pay close attention to the separation distance 's' calculation to prevent side-flashing to internal metallic services, which can cause fires and damage sensitive equipment.
Frequently referenced clauses
copperaluminiumgalvanized steelearthing
International Equivalents
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International Comparison — Coming Soon
We're adding equivalent international standards for this code.
Key Values6
Quick Reference Values
Rolling sphere radius for LPL I20 m
Rolling sphere radius for LPL IV60 m
Minimum cross-section for copper down-conductor tape50 mm²
Minimum thickness of steel sheet as natural air-terminator4 mm
Maximum mesh size for air-termination (LPL I)5 m x 5 m
Recommended earth resistance for LPS< 10 Ohms
Key Formulas
s = ki * (kc / km) * l — Separation distance to prevent dangerous sparking
Tables & Referenced Sections
Key Tables
Table 3 - Lightning protection levels (LPL)
Table 4 - Minimum thickness of metal sheets or pipes in air-termination systems
Table 6 - Material, configuration and minimum cross-sectional area for air-termination conductors, air-termination rods and down-conductors
Table 7 - Material, configuration and minimum dimensions of earth electrodes
Key Clauses
Clause 5 - Lightning Protection System (LPS)
Clause 6 - External Lightning Protection System
Clause 8 - Maintenance and inspection of an LPS
Annex A - Positioning of the air-termination system
Annex D - Calculation of separation distance 's'
Frequently Asked Questions4
What is the rolling sphere method?+
It's a geometric method to determine the placement of air terminals. A sphere of a radius defined by the LPL (e.g., 20m for LPL I) is 'rolled' over the structure; any part of the structure the sphere cannot touch is considered a protected zone.
What is the minimum cross-section for a copper down-conductor strip?+
50 mm², with a minimum thickness of 2 mm (Table 6).
How often should a lightning protection system be tested?+
Complete inspection and testing should be done at intervals not exceeding 2-4 years for standard structures, and more frequently (e.g., 1-2 years) for critical systems or in highly corrosive environments (Clause E.7).
What is the difference between IS/IEC 62305 Part 3 and Part 4?+
Part 3 deals with protecting the structure itself from physical damage and protecting people from injury. Part 4 deals with protecting the internal electrical and electronic systems from the effects of lightning electromagnetic impulse (LEMP).
QA/QC Inspection Templates
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QA/QC templates coming soon for this code.