1. Electricity at Work

2. Basic Principles of Electricity
Volt = Electrical pressure
Ampere = Electric current flow
Ohm = Electrical resistance (or impedance)
Power (watts) = voltage x current

3. Electrical Hazards Electric shocks Electric burns Electrical fires
Electric arcing
Explosion
Portable Electrical equipment

4. Electrical Control Measures
Insulation/Enclosure of live parts
Low Voltages
Earthing
Fuse
Circuit Breaker
RCD
Equipotential bonding
Isolation

5. Insulation/Enclosure of Live Parts
Live parts cannot be touched
If equipment has a metal enclosure, precautions must be taken to prevent metalwork becoming live. This is achieved by double insulation in which live parts are covered by 2 layers of insulator.
Each layer is capable of adequate insulation

6. Low Voltages
For hand tools, the 100 volt centre-tapped (CTE) system is recommended.
System relies on the mid-point of the reduced voltage transformer to be earthed
Maximum shock voltage is 55 volts, but full 110 volt supply powers the equipment

7. Earthing
By connecting exposed metal parts to earth, any fault current is provided with low impedance path to earth I.e. one with little resistance so that fault current will operate protective devices and cut off the supply by breaking the circuit
If all exposed metalwork is properly bonded to earth, it cannot be made live by a fault and the risk of shock is eliminated.

8. Fuses
Forms a weak link in a circuit by overheating and melting by design if the current exceeds the safe limit
Rating should be above operating current required by equipment but less than the current rating of the cable in the circuit

9. Circuit Breakers
A mechanical switch which automatically opens if the circuit is overloaded
Rating should be above operating current required by equipment but less than the current rating of the cable in the circuit

10. RCDs Interrupt supply in event of a small leak of current to earth
Sensitivity can be adjusted so that shocks are not lethal
Determine when a current flows to earth by comparing current in live and neutral conductors
Test buttons should be regularly checked

11. Equipotential Bonding
All extraneous metalwork is is connected by a common bonding conductor which ensures that all the metalwork is at the same potential
Current will not flow between two points at the same potential
A common connection to earth is usually made

12. Isolation
Isolation means depriving something of power, AND ensuring that tit cannot be re-energised
Establishes an effective barrier between equipment and supply and ensures that no unauthorised person is able to remove the barrier
Should be clearly labelled

13. Other Control Measures
Insulating gloves
Insulating mats
FR clothing
Insulated tools
Face shields
Shrouding
Distance

14. Portable Electrical Equipment Control Measures
Regular checks/maintenance
Roll out leads
Do not use in harsh conditions
Manufacturers instructions
110v CTE system

15. Electricity at Work Regs 1989
Require that all electrical systems should be:
Constructed & maintained to prevent danger
Regularly checked & tested by a competent person
Suitable & sufficient for the environment in which they are to be used
Protected by earthing, double earthing, double insulation and/or RCDs
Capable of being made dead (isolated)
Live working should only be used as a last resort and then with all due precautions to prevent/minimise injury
Systems should normally be made dead, checked and isolated so that they cannot accidentally become energised – may require PtW systems

16. Maintaining Electrical Equipment
User checks
Formal visual inspections
Combined Inspections and tests
Maintenance and test records
Frequency of maintenance

17. User Checks
Check for:
Damage to cable sheath
Damage to plug, casing or pins
Inadequate joints or taped joints
Coloured internal cables showing
Wet or contamination
Damage to external casing or loose parts or screws
Equipment should be taken out of use and reported immediately

18. Formal Visual Inspections
Carried out by competent person
Most faults can be picked up this way
Include removal of plug cover and checking fuse
Provide simple written guidance
Faulty equipment should be taken out of service and not used until properly repaired
Data should be kept and can be used to identify trends

19. Combined Inspection & Test
Likely to be justified when:
Reason to suspect equipment may be faulty
After repair or modification
At periods appropriate to the equipment
PAT testing

20. Maintenance & Test Records
Useful for reviewing & monitoring effectiveness of maintenance regime
Can be used as inventory of equipment and a check on use of unauthorised equipment
Can be used to identify trends
Useful to label equipment

21. Frequency of Inspections
Factors to consider:
Type of equipment e.g. portable or hand held
Manufacturers recommendations
Initial integrity and soundness
Age of equipment
Working environment e.g. wet , hot, dusty
Frequency and duration of use
Foreseeable abuse of equipment
Effects of any modifications or repairs
Analysis of records of previous maintenance

22. Effects of Electric Shock
Muscular contractions
Respiratory failure
Fibrillation of the heart
Cardiac arrest
Burns
Can result in secondary injuries e.g. falls from height or muscle tears

23. First Aid for Electric Shock
Break contact between current and victim either by switching off or removing victim
Ensure rescuer does not come into contact with anything live e.g. victims skin
Artificial respiration should commence immediately and continue until the victim recovers or qualified medical aid intervenes