Course Title

1. Introduction to Medium Voltage Electrical Safety

• Medium voltage definition — 1 kV to 36 kV — and its distinction from low-voltage systems in hazard severity

• Regulatory framework including (NFPA 70E: Standard for Electrical Safety in the Workplace, IEEE 1584: Guide for Performing Arc-Flash Hazard Calculations, OSHA 29 CFR 1910.269, and OSHA 29 CFR 1910.333)

• Qualified person definition per NFPA 70E and OSHA 29 CFR 1910.269 — and the training obligation before performing any medium voltage work

• Medium voltage equipment types in industrial environments including (switchgear, ring main units, transformers, cable terminations, and motor control centres)

• Medium voltage incident statistics — arc flash fatality rate, shock contact mortality at MV levels, and primary causes of MV electrical incidents

2. Electrical Hazards — Shock and Arc Flash

• Electric shock physiology including (current path through the body, ventricular fibrillation threshold at 50–100 mA, and tissue burn from contact with MV conductors)

• Touch potential and step potential hazards near medium voltage ground faults

• Arc flash physics including (arc plasma temperature up to 20,000°C, pressure wave, molten metal ejection, and UV radiation — all occurring within milliseconds)

• Incident energy definition per IEEE 1584 — energy in cal/cm² at the working distance during an arc flash event

• Arc flash severity at medium voltage — significantly higher incident energy than low-voltage systems at equivalent fault current levels

• Induced voltage hazards from working near energized MV cables and overhead lines — relevant for cable installation and substation maintenance

• Applying HIRARC to medium voltage work tasks — identifying shock, arc flash, induced voltage, and capacitive stored energy hazards

3. Approach Boundaries and Arc Flash Labels

• Approach boundary types per NFPA 70E including (Limited Approach Boundary — unqualified persons may not cross without escort, Restricted Approach Boundary — only qualified persons with shock PPE, and Arc Flash Boundary — arc-rated PPE required)

• Arc Flash Boundary definition — the distance at which incident energy equals 1.2 cal/cm² per NFPA 70E

• Shock protection boundaries at medium voltage — Restricted Approach Boundary distances increase significantly versus low-voltage equivalents

• Arc flash label content per NFPA 70E Section 130.5(H) including (incident energy or PPE category, arc flash boundary, working distance, and nominal voltage)

• Reading and applying an arc flash label — the practical skill that precedes every task near MV equipment

• When arc flash labels are absent — applying conservative PPE selection until a label or arc flash study is available

4. Electrically Safe Work Condition and LOTO

• Electrically safe work condition per NFPA 70E — the mandatory six-step procedure before any work on MV equipment

• Step 1 — identify all sources of energy including (primary supply, back-feed, and capacitive stored energy in MV cables)

• Step 2 — interrupt the load current before opening isolating devices

• Step 3 — open all isolating devices — disconnects, circuit breakers, and fuses

• Step 4 — apply Lockout/Tagout — LOTO per OSHA 29 CFR 1910.147 to all isolation points

• Step 5 — release or restrain stored energy including (discharge MV cable capacitance through earthing and short-circuiting)

• Step 6 — verify absence of voltage using a correctly rated voltage detector — test before touch on all phase conductors

• LOTO group isolation for MV systems — lock box management and multi-craft authorization for complex MV isolation schemes

• Temporary earthing and short-circuiting — selection, connection sequence, and the prohibition on removing earthing without verified re-isolation

5. Arc-Rated PPE Selection and Inspection

• Arc-rated PPE categories per NFPA 70E Table 130.5(G) including (Category 1 — minimum 4 cal/cm², Category 2 — minimum 8 cal/cm², Category 3 — minimum 25 cal/cm², and Category 4 — minimum 40 cal/cm²)

• Incident energy analysis method — selecting PPE with arc rating exceeding the calculated incident energy from the IEEE 1584 arc flash study

• PPE categories method — selecting the category from the NFPA 70E task table where incident energy analysis is not available

• Arc-rated clothing components including (arc-rated face shield or arc flash suit hood, arc-rated jacket and trousers or coverall, arc-rated gloves, and leather safety boots)

• Rubber insulating gloves for shock protection — voltage class selection for MV work and leather protector requirement

• Arc-rated PPE inspection before use including (checking for damage, contamination, and arc rating label legibility — and withdrawal of damaged PPE)

• What arc-rated PPE does not protect against — it limits burns to survivable levels but does not prevent blast pressure injury at very high incident energies

6. HSE, Quality, and Safe Work Practices

• Energized electrical work justification per NFPA 70E — work on energized MV equipment requires documented justification that de-energization is infeasible or creates greater hazard

• Energized electrical work permit — completing the task-specific risk assessment before any justified energized MV work

• Single-line diagram review before every MV task — confirming the isolation scheme, confirming back-feed sources, and confirming earthing point locations

• Test before touch — mandatory voltage verification with a correctly rated voltage detector before any conductor contact

• Integration within the ISO 45001:2018 HSE management system including (MV electrical hazards in the risk register and permit-to-work for all MV work)

• Quality management per ISO 9001 including (LOTO records, PPE inspection records, voltage test records, and energized work permits)

• Continual improvement applying PDCA — Plan-Do-Check-Act to MV electrical safety program performance

7. Emergency Response and Case Studies

• Response to MV electrical contact — never touch the victim while the circuit is live, isolate the supply, and call emergency services before approaching

• Arc flash injury response including (cooling burns with cool running water for minimum 20 minutes, removing smouldering but not adhered clothing, and calling emergency services immediately)

• Electrical fire response — Class C extinguisher for energized electrical equipment, de-energize before applying other extinguisher types, and evacuation criteria for MV switchgear fire

• Post-incident equipment management — never re-energizing MV equipment after an arc flash event without engineering inspection and authorization

• Case studies from MV electrical incidents in Middle East industrial, petrochemical, and utility environments including (arc flash fatalities from energized MV switchgear work without PPE, contact fatalities from absence of voltage verification, and isolation failures from incomplete LOTO on back-fed MV cables) and the importance of proper MV electrical safety training

• Group discussion on MV electrical safety challenges in regional environments including (managing LOTO discipline on complex MV distribution systems during petrochemical turnarounds, and enforcing energized work justification against production pressure to avoid shutdown)

• Applying RCA to MV electrical incidents — identifying procedural, training, and system root causes and developing corrective actions