Lightning Protection System (LPS) in Mines – DGMS Guidelines, Installation Standards & Safety MCQs

🧾 DETAILED NOTES

1️⃣ Introduction

Lightning strikes are one of the most unpredictable and destructive natural phenomena. In mining areas, lightning can cause electrical surges, fires, explosions, and fatal accidents, especially around coal stockyards, oil storage tanks, and mine substations. To minimize such hazards, every surface installation in mines must be protected by a Lightning Protection System (LPS) designed and maintained as per DGMS circulars and Indian Standards (IS/IEC 62305).

2️⃣ DGMS and Statutory Provisions

Regulation / Standard	Description
CMR 2017 – Reg. 131A	Mandates protection against lightning in surface and underground installations.
DGMS Circular 1 of 2016	Guidelines for design, testing, and maintenance of lightning protection systems.
DGMS Circular 3 of 2018	Specifies periodic testing and resistance limits for earthing systems.
IS/IEC 62305 (Part 1–4)	Indian Standard for lightning protection design and risk management.
Mines Act, 1952 – Sec. 18	Safety in electrical installations including lightning.

3️⃣ Purpose of Lightning Protection System (LPS)

Protect human life and mine property.
Prevent fire or explosion in areas storing coal dust, fuel, or explosives.
Provide safe discharge path for lightning energy to earth.
Avoid electrical surges damaging communication and control systems.

4️⃣ Components of LPS

Component	Function
Air Terminal (Lightning Rod)	Captures the lightning strike.
Down Conductor	Conducts discharge current to the earth.
Earth Electrode (Earth Pit)	Safely dissipates energy into the ground.
Bonding Conductors	Equalize potential to prevent side flashing.
Surge Protection Device (SPD)	Protects sensitive electrical equipment from voltage spikes.

5️⃣ Installation Guidelines

LPS must cover all exposed structures like offices, sub-stations, magazines, fuel storage, headgear, workshops, etc.
Lightning conductor should extend at least 3 m above the structure.
Earth resistance should not exceed 10 ohms under dry conditions.
Down conductors must be installed symmetrically for proper current distribution.
All joints and clamps must be mechanically strong and corrosion resistant.
Separate earthing pits should be used for lightning and power systems.
Testing terminal must be provided for each electrode.

6️⃣ Maintenance and Testing

Visual inspection: Every 3 months before monsoon.
Testing: Earth resistance to be tested once every six months.
Recording: Test results must be entered in the Lightning Protection Register.
Repairs: Damaged rods, corroded joints, or broken conductors must be replaced immediately.
DGMS Compliance: Annual inspection certificate to be submitted to DGMS electrical region.

7️⃣ Common Hazards Without LPS

Fire in coal stacks or explosive stores.
Electric shock to workers.
Damage to electrical circuits and communication systems.
Fatal strikes near headgear or conveyors.

⚙️ QUICK ONE-LINERS (Revision Points)

CMR Reg. 131A – Protection against lightning.
IS/IEC 62305 – Lightning protection design standard.
Earth resistance ≤ 10 ohms.
DGMS Circular 1/2016 – LPS design & testing.
DGMS Circular 3/2018 – Earthing resistance measurement.
Lightning rods must be ≥ 3 m above structure.
Separate earthing for lightning and power.
Half-yearly testing mandatory.
Register must record results & inspection dates.
Surge protection devices (SPD) safeguard electronics.

🧩 DESCRIPTIVE MODEL QUESTION

Q. Describe the design, installation, and maintenance requirements of a Lightning Protection System (LPS) in mines as per DGMS guidelines.

Answer:
As per CMR 2017 Reg. 131A and DGMS Circular 1/2016, every surface installation in mines must have an LPS. It comprises air terminals, down conductors, and earth electrodes connected by copper or GI strips. The lightning rod must rise at least 3 m above the highest point, and the earth resistance should not exceed 10 ohms. All systems must be tested half-yearly (every 6 months) and recorded in the Lightning Protection Register. Proper LPS prevents fire, shock, and equipment damage from lightning strikes.

🧮 25 DGMS-Based MCQs (5 Options Each)

Q1. Regulation dealing with lightning protection in mines:

Solution: Regulation 131A of CMR 2017 specifically mandates protection against lightning.

Q2. DGMS Circular for lightning protection system:

Solution: DGMS Circular 1 of 2016 provides the detailed guidelines for designing, installing, and testing LPS.

Q3. Standard followed for LPS design:

Solution: IS/IEC 62305 is the comprehensive Indian Standard (aligned with International standards) for lightning protection, which DGMS refers to. IS 3043 is for general earthing.

Q4. Maximum permissible earth resistance for LPS:

Solution: The earth resistance of the LPS earthing system should be maintained as low as possible, not exceeding 10 ohms.

Q5. Frequency of LPS testing:

Solution: Earth resistance and system integrity must be tested at least once every six months (half-yearly), especially before the monsoon season.

Q6. Lightning conductor height above structure:

Solution: The air terminal (lightning rod) should typically extend at least 3 meters above the highest point of the structure it is protecting.

Q7. Earth electrodes for lightning should be:

Solution: It is a critical safety requirement to keep the lightning earthing pit separate from the main power system earthing to prevent surges from entering the power lines.

Q8. LPS includes:

Solution: A complete LPS consists of all these components working together to capture, conduct, and dissipate the lightning strike.

Q9. Lightning counter used to:

Solution: A lightning counter is installed on the down conductor to record how many times the system has been struck.

Q10. DGMS Circular 3/2018 refers to:

Solution: This circular provides guidelines on measuring and maintaining earthing resistance for electrical systems and LPS.

Q11. Lightning energy dissipated through:

Solution: The down conductor provides a safe path for the high-energy current to travel from the air terminal to the earth electrode.

Q12. Material commonly used for down conductor:

Solution: Copper or Galvanized Iron (GI) strips are used due to their high conductivity and durability.

Q13. LPS register maintained by:

Solution: The competent Electrical Engineer or Supervisor is responsible for testing and maintaining the LPS register.

Q14. DGMS mandates testing interval of:

Solution: Testing is required half-yearly (every 6 months) to ensure the system is functional before the lightning season.

Q15. Equipotential bonding prevents:

Solution: Bonding connects all metal components to the same potential, preventing dangerous sparks (side flashing) and touch potential.

Q16. LPS protects against:

Solution: An LPS protects against the direct strike (fire risk) and the resulting electrical surge (surge risk).

Q17. Recommended earthing conductor size (minimum):

Solution: 25 mm² copper or 50 mm² GI/Steel is often cited as a minimum size for down conductors/earthing strips in standards like IS 3043.

Q18. LPS resistance measured with:

Solution: A dedicated Earth Tester (often called a Megger, which is a brand name) is used to measure earth pit resistance.

Q19. Testing terminal provided for:

Solution: A test link/terminal is installed to disconnect the earth electrode from the system for periodic resistance measurement.

Q20. LPS failures often due to:

Solution: All these maintenance issues can lead to high resistance or a break in the path, causing the LPS to fail.

Q21. Standard for risk assessment in LPS:

Solution: Part 2 of the IS/IEC 62305 standard specifically covers Risk Management for lightning protection.

Q22. Earth pit identification must include:

Solution: Proper identification tags must include all relevant details for inspection and record-keeping.

Q23. LPS should be inspected before:

Solution: A thorough inspection and testing regime is mandatory before the onset of the monsoon (lightning season) to ensure it is working.

Q24. Surge Protection Devices are connected at:

Solution: SPDs are installed at all critical electrical and data entry points to protect sensitive equipment from surges.

Q25. DGMS-approved LPS ensures:

Solution: A properly functioning LPS protects the structure from fire, personnel from shock, and equipment from electrical surges.

🔗 INTERNAL LINKS

Related Topic	Read More On...
Electrical Safety	Electrical Safety & Accident Investigation
Electrical Training	DGMS Training Syllabus for Electrical Engineers
CMR 2017	CMR 2017 Part 2 - Working & Supervision Rules
DGMS Circulars	DGMS General Circular No. 01 of 2023

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