Part 4 is one of the largest and the most important Parts within BS7671 and forms 25% of your final 2382-12 exam…
Breaks down into four individual Chapters.
Chapter 41: Protection Against Electric Shock
Contains methods used to reduce the risks of electric shock within an electrical installation and covers both methods of basic and fault protection, as such you’ll find the maximum Zs tables ie (T41.3 pg 56) are within this chapter. Remember; Automatic Disconnection of Supply (ADS) is the most commonly used protective method. Other methods of protection covered are Double or Reinforced Insulation, Electrical Separation, Extra Low Voltage – SELV & PELV.
Chapter 42: Protection Against Thermal Effects
All about the protection of persons, livestock and property from the effects of heat from electrical equipment, ignition, combustion and smoke. The prevention of spread of fire and the loss of safety services due to a fire.
So anything to do with heat, fire or smoke is all in this chapter.
Chapter 43: Protection Against Overcurrent
Probably one of the easier Chapters to define. Chapter 43 covers anything concerning overloads including faults which are overloads due to fault conditions ie Line to Neutral (Short Circuit) and Line to Earth (Earth Fault).
Key parts are, co-ordination between conductors and overload protective device 433.1 and determination of prospective fault current (PSCC and PEFC) 434.1. Also within this Chapter is the regulation that gives us 30 or 32 amp ring circuits 433.1.103. One thing that’s not mentioned is the prospective fault current for a three phase installation is twice the PSCC (prospective short circuit current). Worth remembering as a favourite exam question.☺
Chapter 44: Protection Against Voltage Disturbances and Electromagnetic Disturbances
Out of all the four Chapters this usually has the least amount of questions asked on the exam.
Key areas seem to be 443 in particular T44.3 and T44.4 (impulse withstand voltage and categories of equipment). Section 444 is new to 17th and formed part of Ammendment 1 and covers electromagnetic disturbances, measures to reduce EMI 444.4.2. Bonding networks and the CSA of earthing busbars. 445 covers undervoltage.