DGMS Circular No. 10 of 2020 – Lightning Protection in Mines (Notes + MCQs)

📘 Detailed Notes – DGMS (Tech) Circular No. 10 of 2020 Subject:

Protection Against Lightning in Mines
Issued by: DGMS, Dhanbad
Date: 23.06.2020
Applies to: Owners, Agents & Managers of all mines

🔹 1. Background

Increasing incidents of lightning strikes in mines → accidents involving persons, machinery, and installations.

Need for risk assessment, protection systems, and earthing arrangements to safeguard workers and mine infrastructure.

🔹 2. Risk Assessment

Each mine must conduct a Lightning Risk Assessment Study.

Calculation basis:

IS-2309 or IS/IEC-62305 standards.

Risk measured as Expected number of lightning flashes per sq. km/year.

Threshold:

If > 10⁻⁵ (1 in 100,000 chance) → mandatory lightning protection required.

🔹 3. Areas Requiring Mandatory Protection Even if exposure risk is moderate, lightning protection must be provided at:

⚡ Places where large numbers of people congregate.

💣 Blasting operation sites.

📦 Explosive storage magazines.

⚡ Overhead power lines passing through mine boundary.

💧 Pumping installations with continuous operator presence.

⛰️ Top of OB dump yards (high, exposed, lightning-prone).

🔹 4. Lightning Protection Systems (LPS) Different systems based on application: 4.1 Conventional Air Terminal (Franklin Rod/Conductor)

Protects within 45° Zone of Protection (ZP).

For critical areas, ZP reduced to 30°.

Must cover blasting sites, people congregation areas, etc.

4.2 Meshed Conductor Network (Faraday’s Cage)

Electrostatic shielding using metallic wires in criss-cross.

Grounded at minimum two independent points.

Protects substations, switchyards, explosive rooms, etc.

4.3 Ionizing Air Terminal (Early Streamer Emission – ESE)

Generates upward streamer to capture downward lightning.

Must conform to Indian/International Standards (IEC).

Must be NABL tested before installation.

4.4 IEC 62305-3 Compliance

Protection of oil mines and other critical installations as per IEC standards.

🔹 5. Earthing Systems for LPS

Key principle: Lightning pulse must be safely discharged to earth.

Must comply with IS-3043 (Earthing Code).

Requirements:

Earthing for LPS must be independent from general grounding system.

Collective earth resistance ≤ 2 ohm (or as per standards).

Prevent risks of conduction, induction & feedback.

Remote earthing to be used if local conditions unfavorable (e.g., OB dumps, quarry sites).

🔹 6. Record Keeping

Mines must maintain records of:

Lightning risk assessment surveys.

Installation details of LPS.

Maintenance schedules and inspection reports.

🔹 7. Responsibilities

Owners, Agents & Managers → Ensure strict compliance.

Failure may lead to accidents, statutory violations, and penalties.

📊 Exam Key Points

Circular No. → 10 of 2020

Standard references → IS-2309, IS/IEC-62305, IS-3043, IEC-62305-3

Protection systems → Franklin Rod, Faraday Cage, ESE

Earthing → Independent, resistance ≤ 2Ω, remote earthing if needed

Critical areas → Explosives, OB dump top, pump installations, overhead lines, blasting zones, congregation areas

ZP angle → 45° normal, 30° for critical areas

📘 MCQs on DGMS Circular No. 10 of 2020 – Lightning Protection in Mines

Q1. ⚡ The main purpose of DGMS Circular No. 10 of 2020 is:

A. Fire prevention
B. Protection against lightning
C. Dust suppression
D. Noise reduction
E. Explosives handling
✅ Answer: B
📝 Ensures safety of persons, machinery & installations from lightning hazards.

Q2. 📊 Risk assessment for lightning must be done using:

A. IS-3043 only
B. IS-2309 or IS/IEC-62305
C. Indian Explosives Rules
D. Mines Act, 1952
E. Mines Rescue Rules, 1985
✅ Answer: B
📝 Circular mandates risk assessment as per IS-2309 or IS/IEC-62305.

Q3. 🔢 Protection is mandatory if lightning flash probability exceeds:

A. 1 in 1000
B. 1 in 10,000
C. 1 in 100,000
D. 1 in 1,000,000
E. 1 in 10
✅ Answer: C
📝 If >10⁻⁵ (1 in 100,000), LPS must be installed.

Q4. 🏭 Which area requires lightning protection even in moderate risk?

A. Rest shelters
B. Blasting sites
C. First aid rooms
D. Vehicle parking
E. Survey office
✅ Answer: B
📝 Circular highlights blasting areas as critical.

Q5. 💣 Which site is NOT specifically listed as needing lightning protection?

A. Explosive magazines
B. OB dump top
C. Pumping installations
D. Canteen
E. Overhead lines
✅ Answer: D
📝 Canteen not listed, others are mandatory.

Q6. ⚒️ Franklin rod provides protection within:

A. 15° Zone
B. 30° Zone
C. 45° Zone
D. 60° Zone
E. 90° Zone
✅ Answer: C
📝 Standard Zone of Protection = 45°.

Q7. 🏗️ For critical areas, Franklin rod’s ZP angle is reduced to:

A. 90°
B. 75°
C. 60°
D. 30°
E. 15°
✅ Answer: D
📝 Circular reduces to 30° for fool-proof protection.

Q8. 🛡️ Meshed Conductor Network is also known as:

A. Lightning net
B. Faraday’s Cage
C. Grounding mesh
D. Static shield
E. Earth mesh
✅ Answer: B
📝 Faraday cage provides electrostatic shielding.

Q9. 🔌 Minimum independent grounding points for Faraday cage:

A. 1
B. 2
C. 3
D. 4
E. 5
✅ Answer: B
📝 Must be grounded at minimum 2 independent points.

Q10. 🌩️ ESE stands for:

A. Enhanced Static Earthing
B. Early Streamer Emission
C. Emergency Safety Equipment
D. Electrical Safety Earthing
E. Extra Shielding Earthing
✅ Answer: B
📝 Early Streamer Emission captures lightning preferentially.

Q11. 🧪 ESE system must be tested in:

A. Local mine lab
B. NABL/International Lab
C. Manager’s office
D. DGMS office
E. Rescue station
✅ Answer: B
📝 Testing in NABL/recognized labs is mandatory.

Q12. 📘 Lightning protection for oil mines must follow:

A. IS-2309
B. Mines Act
C. IEC 62305-3
D. Explosive Rules
E. Rescue Code
✅ Answer: C
📝 IEC 62305-3 applies for oil mines.

Q13. 🗂️ Mines must maintain records of:

A. Lightning surveys
B. LPS maintenance
C. Installation details
D. All of the above
E. None
✅ Answer: D
📝 Complete record keeping is compulsory.

Q14. ⚡ Earth resistance of LPS must be ≤: A. 5 Ω
B. 4 Ω
C. 3 Ω
D. 2 Ω
E. 1 Ω
✅ Answer: D
📝 Collective resistance ≤ 2 ohms.

Q15. 🌍 Earthing for LPS must be:

A. Connected to power earthing
B. Independent of other grounding
C. Shared with pumping system
D. Only water pipe earthing
E. None
✅ Answer: B
📝 Independent earthing avoids feedback risks.

Q16. 🪨 Remote earthing is used when:

A. Electricity is weak
B. Local grounding is poor
C. OB dumps are too high
D. Blasting is ongoing
E. Lightning is rare
✅ Answer: B
📝 Remote earthing required if soil unsuitable.

Q17. ⛰️ OB dump yards are vulnerable because:

A. Low height
B. Loose material
C. Exposed elevation
D. Presence of trees
E. Constant traffic
✅ Answer: C
📝 High elevation attracts lightning.

Q18. 🧲 Earthing system must prevent:

A. Induction
B. Conduction
C. Feedback
D. All of the above
E. None
✅ Answer: D
📝 Designed to avoid all three risks.

Q19. 🚨 Lightning arrestors must be installed at:

A. Magazines
B. Tall structures
C. Pumping areas
D. OB dumps
E. All of the above
✅ Answer: E
📝 All critical installations need arrestors.

Q20. 📜 This circular was issued in year:

A. 2018
B. 2019
C. 2020
D. 2021
E. 2022
✅ Answer: C
📝 Dated 23 June 2020.

Q21. 👨‍💼 Compliance responsibility lies with: A. Blaster
B. Geologist
C. Manager/Agent/Owner
D. Surveyor
E. Mines Rescue Officer
✅ Answer: C
📝 Circular directly addresses Owners/Agents/Managers.

Q22. 🏗️ What is “Zone of Protection” (ZP)? A. Area affected by lightning
B. Area protected by Franklin rod
C. Ground earthing system
D. Pumping installation
E. Quarry slope zone
✅ Answer: B
📝 ZP defines area safeguarded by conductor.

Q23. ⚡ Main cause of incidents leading to this circular:

A. Dust explosions
B. Lightning accidents
C. Mine inundation
D. Fire hazards
E. Roof falls
✅ Answer: B
📝 Issued due to increasing lightning accidents.

Q24. ⛏️ If LPS not provided, hazards may include:

A. Person injury
B. Machinery damage
C. Explosives detonation
D. All of the above
E. None
✅ Answer: D
📝 All risks possible without protection.

Q25. 📘 The earthing system for LPS should follow standard:

A. IS-2309
B. IS-3043
C. IEC-62305-3
D. Mines Act
E. Explosives Act
✅ Answer: B
📝 IS-3043 governs earthing design.

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DGMS Circular No. 10 of 2020 – Lightning Protection in Mines (Notes + MCQs)

📘 Detailed Notes – DGMS (Tech) Circular No. 10 of 2020 Subject:

A. Fire prevention B. Protection against lightning C. Dust suppression D. Noise reduction E. Explosives handling ✅ Answer: B 📝 Ensures safety of persons, machinery & installations from lightning hazards. Q2. 📊 Risk assessment for lightning must be done using:

A. IS-3043 only B. IS-2309 or IS/IEC-62305 C. Indian Explosives Rules D. Mines Act, 1952 E. Mines Rescue Rules, 1985 ✅ Answer: B 📝 Circular mandates risk assessment as per IS-2309 or IS/IEC-62305. Q3. 🔢 Protection is mandatory if lightning flash probability exceeds:

A. 1 in 1000 B. 1 in 10,000 C. 1 in 100,000 D. 1 in 1,000,000 E. 1 in 10 ✅ Answer: C 📝 If >10⁻⁵ (1 in 100,000), LPS must be installed. Q4. 🏭 Which area requires lightning protection even in moderate risk?

A. Rest shelters B. Blasting sites C. First aid rooms D. Vehicle parking E. Survey office ✅ Answer: B 📝 Circular highlights blasting areas as critical. Q5. 💣 Which site is NOT specifically listed as needing lightning protection?

A. Explosive magazines B. OB dump top C. Pumping installations D. Canteen E. Overhead lines ✅ Answer: D 📝 Canteen not listed, others are mandatory. Q6. ⚒️ Franklin rod provides protection within:

A. 15° Zone B. 30° Zone C. 45° Zone D. 60° Zone E. 90° Zone ✅ Answer: C 📝 Standard Zone of Protection = 45°. Q7. 🏗️ For critical areas, Franklin rod’s ZP angle is reduced to:

A. 90° B. 75° C. 60° D. 30° E. 15° ✅ Answer: D 📝 Circular reduces to 30° for fool-proof protection. Q8. 🛡️ Meshed Conductor Network is also known as:

A. Lightning net B. Faraday’s Cage C. Grounding mesh D. Static shield E. Earth mesh ✅ Answer: B 📝 Faraday cage provides electrostatic shielding. Q9. 🔌 Minimum independent grounding points for Faraday cage:

A. 1 B. 2 C. 3 D. 4 E. 5 ✅ Answer: B 📝 Must be grounded at minimum 2 independent points. Q10. 🌩️ ESE stands for:

A. Enhanced Static Earthing B. Early Streamer Emission C. Emergency Safety Equipment D. Electrical Safety Earthing E. Extra Shielding Earthing ✅ Answer: B 📝 Early Streamer Emission captures lightning preferentially. Q11. 🧪 ESE system must be tested in:

A. Local mine lab B. NABL/International Lab C. Manager’s office D. DGMS office E. Rescue station ✅ Answer: B 📝 Testing in NABL/recognized labs is mandatory. Q12. 📘 Lightning protection for oil mines must follow:

A. IS-2309 B. Mines Act C. IEC 62305-3 D. Explosive Rules E. Rescue Code ✅ Answer: C 📝 IEC 62305-3 applies for oil mines. Q13. 🗂️ Mines must maintain records of:

A. Connected to power earthing B. Independent of other grounding C. Shared with pumping system D. Only water pipe earthing E. None ✅ Answer: B 📝 Independent earthing avoids feedback risks. Q16. 🪨 Remote earthing is used when:

A. Electricity is weak B. Local grounding is poor C. OB dumps are too high D. Blasting is ongoing E. Lightning is rare ✅ Answer: B 📝 Remote earthing required if soil unsuitable. Q17. ⛰️ OB dump yards are vulnerable because:

A. Low height B. Loose material C. Exposed elevation D. Presence of trees E. Constant traffic ✅ Answer: C 📝 High elevation attracts lightning. Q18. 🧲 Earthing system must prevent:

A. Induction B. Conduction C. Feedback D. All of the above E. None ✅ Answer: D 📝 Designed to avoid all three risks. Q19. 🚨 Lightning arrestors must be installed at:

A. Magazines B. Tall structures C. Pumping areas D. OB dumps E. All of the above ✅ Answer: E 📝 All critical installations need arrestors. Q20. 📜 This circular was issued in year:

A. Dust explosions B. Lightning accidents C. Mine inundation D. Fire hazards E. Roof falls ✅ Answer: B 📝 Issued due to increasing lightning accidents. Q24. ⛏️ If LPS not provided, hazards may include:

A. Person injury B. Machinery damage C. Explosives detonation D. All of the above E. None ✅ Answer: D 📝 All risks possible without protection. Q25. 📘 The earthing system for LPS should follow standard:

A. IS-2309 B. IS-3043 C. IEC-62305-3 D. Mines Act E. Explosives Act ✅ Answer: B 📝 IS-3043 governs earthing design.

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A. Fire prevention
B. Protection against lightning
C. Dust suppression
D. Noise reduction
E. Explosives handling
✅ Answer: B
📝 Ensures safety of persons, machinery & installations from lightning hazards.

Q2. 📊 Risk assessment for lightning must be done using:

A. IS-3043 only
B. IS-2309 or IS/IEC-62305
C. Indian Explosives Rules
D. Mines Act, 1952
E. Mines Rescue Rules, 1985
✅ Answer: B
📝 Circular mandates risk assessment as per IS-2309 or IS/IEC-62305.

Q3. 🔢 Protection is mandatory if lightning flash probability exceeds:

A. 1 in 1000
B. 1 in 10,000
C. 1 in 100,000
D. 1 in 1,000,000
E. 1 in 10
✅ Answer: C
📝 If >10⁻⁵ (1 in 100,000), LPS must be installed.

Q4. 🏭 Which area requires lightning protection even in moderate risk?

A. Rest shelters
B. Blasting sites
C. First aid rooms
D. Vehicle parking
E. Survey office
✅ Answer: B
📝 Circular highlights blasting areas as critical.

Q5. 💣 Which site is NOT specifically listed as needing lightning protection?

A. Explosive magazines
B. OB dump top
C. Pumping installations
D. Canteen
E. Overhead lines
✅ Answer: D
📝 Canteen not listed, others are mandatory.

Q6. ⚒️ Franklin rod provides protection within:

A. 15° Zone
B. 30° Zone
C. 45° Zone
D. 60° Zone
E. 90° Zone
✅ Answer: C
📝 Standard Zone of Protection = 45°.

Q7. 🏗️ For critical areas, Franklin rod’s ZP angle is reduced to:

A. 90°
B. 75°
C. 60°
D. 30°
E. 15°
✅ Answer: D
📝 Circular reduces to 30° for fool-proof protection.

Q8. 🛡️ Meshed Conductor Network is also known as:

A. Lightning net
B. Faraday’s Cage
C. Grounding mesh
D. Static shield
E. Earth mesh
✅ Answer: B
📝 Faraday cage provides electrostatic shielding.

Q9. 🔌 Minimum independent grounding points for Faraday cage:

A. 1
B. 2
C. 3
D. 4
E. 5
✅ Answer: B
📝 Must be grounded at minimum 2 independent points.

Q10. 🌩️ ESE stands for:

A. Enhanced Static Earthing
B. Early Streamer Emission
C. Emergency Safety Equipment
D. Electrical Safety Earthing
E. Extra Shielding Earthing
✅ Answer: B
📝 Early Streamer Emission captures lightning preferentially.

Q11. 🧪 ESE system must be tested in:

A. Local mine lab
B. NABL/International Lab
C. Manager’s office
D. DGMS office
E. Rescue station
✅ Answer: B
📝 Testing in NABL/recognized labs is mandatory.

Q12. 📘 Lightning protection for oil mines must follow:

A. IS-2309
B. Mines Act
C. IEC 62305-3
D. Explosive Rules
E. Rescue Code
✅ Answer: C
📝 IEC 62305-3 applies for oil mines.

Q13. 🗂️ Mines must maintain records of:

A. Connected to power earthing
B. Independent of other grounding
C. Shared with pumping system
D. Only water pipe earthing
E. None
✅ Answer: B
📝 Independent earthing avoids feedback risks.

Q16. 🪨 Remote earthing is used when:

A. Electricity is weak
B. Local grounding is poor
C. OB dumps are too high
D. Blasting is ongoing
E. Lightning is rare
✅ Answer: B
📝 Remote earthing required if soil unsuitable.

Q17. ⛰️ OB dump yards are vulnerable because:

A. Low height
B. Loose material
C. Exposed elevation
D. Presence of trees
E. Constant traffic
✅ Answer: C
📝 High elevation attracts lightning.

Q18. 🧲 Earthing system must prevent:

A. Induction
B. Conduction
C. Feedback
D. All of the above
E. None
✅ Answer: D
📝 Designed to avoid all three risks.

Q19. 🚨 Lightning arrestors must be installed at:

A. Magazines
B. Tall structures
C. Pumping areas
D. OB dumps
E. All of the above
✅ Answer: E
📝 All critical installations need arrestors.

Q20. 📜 This circular was issued in year:

A. Dust explosions
B. Lightning accidents
C. Mine inundation
D. Fire hazards
E. Roof falls
✅ Answer: B
📝 Issued due to increasing lightning accidents.

Q24. ⛏️ If LPS not provided, hazards may include:

A. Person injury
B. Machinery damage
C. Explosives detonation
D. All of the above
E. None
✅ Answer: D
📝 All risks possible without protection.

Q25. 📘 The earthing system for LPS should follow standard:

A. IS-2309
B. IS-3043
C. IEC-62305-3
D. Mines Act
E. Explosives Act
✅ Answer: B
📝 IS-3043 governs earthing design.