Electrical Control Measures

Yasir Kayani
Mind Map by Yasir Kayani, updated more than 1 year ago
Yasir Kayani
Created by Yasir Kayani about 5 years ago


Element 5 Page 1

Resource summary

Electrical Control Measures
1 fuses
1.1 form a weak link in a circuit
1.2 designed to overheat and melt if the current exceeds the fuse rating
1.3 rating should be above operating current required by equipment but less than the current rating of the cable in the circuit
1.4 designed to protect the equipment, not people
2 earthing
2.1 by connecting exposed metal parts to earth, any fault current is provided with a low resistance path to earth
2.2 this causes large fault current to flow which blows the fuse
3 isolation
3.1 depriving a circuit of power
3.2 ensuring that it cannot be re-energised by applying some form of lock
3.3 should be clearly labelled
3.4 often referred to as lock-out tag-out
4 insulation
4.1 conductors should either be covered in insulation, or placed in position where they cannot be touched (e.g. underground, over head)
4.2 insulation should be protected from mechanical damage
5 double insulation
5.1 no earth connection required, as any internal part that can become live is covered in 2 layers of insulation
5.2 a double insulated appliance must be labeled Class II, double insulated, or bear the double insulation symbol
6 RCDs
6.1 compare current in live and neutral
6.2 interrupt supply in event of a small leak of current to earth
6.3 very sensitive and very fast
6.4 should be regularly tested
6.5 designed to protect people
7 low voltage
7.1 commonly used for hand tools on construction sites
7.2 110 volt centre-tapped (CTE) system
7.3 system relies on the mid-point of the reduced voltage transformer being earthed
7.4 maximum shock voltage is 55 volts, but full 110 volt supply powers the equipment
7.5 can also replace with battery power
8 competence
8.1 adequate knowledge of electricity
8.2 experience of electrical work
8.3 understanding of class of electrical system
8.4 understanding of hazards and precautions
8.5 ability to continuously assess safety to continue to work
9 safe systems of work
9.1 wherever possible, supply should be isolated before work
9.2 live work should only be conducted if there is no other option and it can be done safely
9.3 additional precautions would be required for live work e.g. shrouding, insulating PPE, insulated tools/mats etc
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