1916356
Description
Mind Map by Yasir Kayani, updated more than 1 year ago
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Created by Yasir Kayani
almost 10 years ago
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Electrical Control Measures
- 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
- form a weak link in a circuit
- 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
- by connecting exposed metal parts to
earth, any fault current is provided with a
low resistance path to earth
- 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
- depriving a circuit of power
- 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
- conductors should either be covered in insulation, or
placed in position where they cannot be touched (e.g.
underground, over head)
- 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
- no earth connection required, as any
internal part that can become live is
covered in 2 layers of insulation
- 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
- compare current in live and neutral
- 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
- commonly used for hand tools on construction sites
- 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
- adequate knowledge of electricity
- 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
- wherever possible, supply should be isolated before work
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