Electrical Control Measures

Electrical Control Measures

1. fuses

   • form a weak link in a circuit
   • designed to overheat and melt if the current exceeds the fuse rating
   • rating should be above operating current required by equipment but less than the current rating of the cable in the circuit
   • designed to protect the equipment, not people

2. earthing

   • by connecting exposed metal parts to earth, any fault current is provided with a low resistance path to earth
   • this causes large fault current to flow which blows the fuse

3. isolation

   • depriving a circuit of power
   • ensuring that it cannot be re-energised by applying some form of lock
   • should be clearly labelled
   • often referred to as lock-out tag-out

4. insulation

   • conductors should either be covered in insulation, or placed in position where they cannot be touched (e.g. underground, over head)
   • insulation should be protected from mechanical damage

5. double insulation

   • no earth connection required, as any internal part that can become live is covered in 2 layers of insulation
   • a double insulated appliance must be labeled Class II, double insulated, or bear the double insulation symbol

6. RCDs

   • compare current in live and neutral
   • interrupt supply in event of a small leak of current to earth
   • very sensitive and very fast
   • should be regularly tested
   • designed to protect people

7. low voltage

   • commonly used for hand tools on construction sites
   • 110 volt centre-tapped (CTE) system
   • system relies on the mid-point of the reduced voltage transformer being earthed
   • maximum shock voltage is 55 volts, but full 110 volt supply powers the equipment
   • can also replace with battery power

8. competence

   • adequate knowledge of electricity
   • experience of electrical work
   • understanding of class of electrical system
   • understanding of hazards and precautions
   • ability to continuously assess safety to continue to work

9. safe systems of work

   • wherever possible, supply should be isolated before work
   • live work should only be conducted if there is no other option and it can be done safely
   • additional precautions would be required for live work e.g. shrouding, insulating PPE, insulated tools/mats etc