Lightning Arrester Design as per NBC & IS Code + Risk Analysis Calculator (2026 Guide) Free Excel download
Lightning protection systems (LPS) are critical for safeguarding buildings against lightning strikes. As per National Building Code of India and IS 2309, every structure must be evaluated for lightning risk and protected accordingly.
This guide covers:
- Lightning arrester design
- Risk assessment method
- IS & NBC guidelines
- โก Risk calculator (included below)
โก Lightning Risk + Down Conductor Calculator (IS 2309)
๐ฅ Building Dimensions
โก Lightning Data
๐ Weighting Factors
โก WHAT IS A LIGHTNING ARRESTER?
A lightning arrester is a device that:
- Intercepts lightning
- Safely conducts it to earth
- Prevents damage to structure & equipment
๐ TYPES OF LIGHTNING PROTECTION SYSTEMS
๐น Conventional System
- Franklin rod
- Down conductor
- Earthing
๐น Early Streamer Emission (ESE)
- Advanced lightning rod
- Larger protection radius
๐ DESIGN REQUIREMENTS (NBC + IS 2309)
๐ฅ Key Requirements:
- Protection for buildings > 15m height
- Proper earthing resistance (< 10 ohms)
- Minimum 2 down conductors
- Bonding of all metallic parts
๐ง RISK ASSESSMENT (MOST IMPORTANT)
Lightning protection is based on:
- Building height
- Location
- Usage
- Lightning density
โก BASIC RISK FORMULA
R=NgโรAeโรCdโ
Where:
- R = Risk
- Ngโ = Lightning ground flash density
- Aeโ = Effective collection area
- Cdโ = Location factor
๐น PART 1: RISK CALCULATION
Formula flow:
- Collection Area
- Probability
- Weighting Factor
- Overall Risk
๐งฎ LIGHTNING RISK CALCULATOR (SIMPLE LOGIC)
๐ฅ Inputs:
- Building length (m)
- Width (m)
- Height (m)
- Ng (lightning density)
- Location factor
๐ Calculation Steps:
1. Effective Area:
2. Risk:
โ DESIGN COMPONENTS
- Air terminals (rods)
- Down conductors
- Earth pits
- Surge protection devices (SPD)
โ COMMON MISTAKES
- Ignoring earthing resistance
- Wrong spacing of conductors
- No bonding
- Not calculating risk
๐ญ RECOMMENDED BRANDS
- OBO Bettermann
- Schneider Electric
- DEHN
- Furse
โ FAQ
What is lightning density (Ng)?
Number of lightning strikes per kmยฒ per year.
Is lightning protection mandatory?
Yes, for high-rise buildings as per NBC.
What is safe earthing resistance?
Below 10 ohms (preferably <5 ohms).
๐ฏ CONCLUSION
Lightning arrester design is not optional โ it is a life safety requirement. Using proper IS code guidelines and risk assessment ensures optimal protection.
Download free AutoCAD DWG files for MEP engineers including plumbing, HVAC, fire alarm, and electrical systems. All drawings are ready to use and based on industry standards.
๐ข Why Download from MEPWORK?
- Free DWG files
- Ready-to-use drawings
- Designed for engineers
- Updated as per industry standards
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The platform is created to solve real-world engineering problems and provide practical tools for faster and more accurate project work.
All resources are regularly updated as per latest standards (NBC 2016, IS Codes, NFPA, and 2026 industry practices).













