Basic Electricity 2, WASSCE (PC), 2017

Question 6

State the regulation guiding the following with respect to installation of earthing:

  1. distance;
  2. cross section of earth continuity conductor;
  3. cross section of earth wire;
  4. electrodes;
  5. earth resistance.

Observation

The expected answers were;

Regulation with respect to earthing

  • Distance:

The distance of the earth electrode from the installation at the premises should not be more than 1.5m.                                                                                         

  • Cross-section of earth continuity conductor:

The size of the earth continuity conductor used in the circuit should not be less than 2.5mm2.                                                                                                                       

  • Cross-Section of earth wire:

The size of the earth wire should be 10mm2 or 16 mm2                                   

  • Electrodes:
  • The earth electrode should be electrically and mechanically strong and should be protected against corrosion.
  • It should be of low resistance.

 

  • Earth resistance:

            The earth resistance should be between 0.5Ω to 1Ω maximum

         Few candidates who attempted this question did not do the question well.