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
Cl. 5Lightning Protection System (LPS)
Cl. 6External Lightning Protection System
Cl. 8Maintenance and inspection of an LPS
Annex A - Positioning of the air-termination system
Annex D - Calculation of separation distance 's'
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
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.