Chapter 4: Protection for Safety

BS 7671 outlines essential protective measures to prevent electrical hazards, ensuring installations remain safe and compliant.

Overview of Chapter 4 – Key Protective Measures

4.1 Protection Against Electric Shock

• Defines methods to **reduce the risk of electric shock** in installations.
• Includes **basic protection** (insulation, barriers) and **fault protection** (earthing, RCDs).
• Automatic Disconnection of Supply (ADS) is the primary method used.
• Other methods include **double insulation, electrical separation, and SELV/PELV systems**.

4.2 Protection Against Thermal Effects

• Ensures **protection against excessive heat** from electrical equipment.
• Prevents **fire hazards, ignition risks, and smoke-related dangers**.
• Includes **fire-resistant enclosures, thermal insulation, and proper ventilation**.

4.3 Protection Against Overcurrent

• Addresses **overload and short-circuit protection**.
• Ensures **correct coordination between conductors and protective devices**.
• Defines **prospective fault current calculations** for circuit design.
• Includes **requirements for circuit breakers, fuses, and overload relays**.

4.4 Protection Against Voltage Disturbances & Electromagnetic Effects

• Minimizes risks from **voltage fluctuations, surges, and electromagnetic interference (EMI)**.
• Includes **impulse withstand voltage requirements** for electrical equipment.
• Defines **bonding networks and earthing busbar specifications**.
• Provides guidance on **reducing EMI in sensitive installations**.

Why Chapter 4 Matters

• Ensures **electrical installations remain safe and reliable**.
• Prevents **electric shock, fire hazards, and equipment failures**.
• Provides **guidelines for selecting protective devices and safety measures**.