Element 6: Electrical

Question 1

Factors influencing the severity of an electric shock

Answer 1

• Voltage of current
• Frequency of current
• Duration of contact
• Current path through body
• Resistance
• Contact surface area
• Environment

Question 2

Common causes of electrical fires

Answer 2

Sparking - the generation of electrical sparks between an uninsulated or poorly insulated conductor and another earthed conductor.

Overheating of conductors - due to poor or inadequate insulation allowing teh natural heat created by the flow of electricity to escape, or excessive resistance in the conductor

Question 3

Causes of workplace electrical equipment accidents include:

Answer 3

• Using unsuitable equipment
• Using equipment in wet, damp or humid conditions
• Misuse
• Physical abuse
• Unauthorised repairs
• Continuing to use equipment knowing it is faulty
• Chemical damage too the flex or tol
• Lck of routine inspection, maintenance or testing

Question 4

High Risks asociated with Electricity

Answer 4

• Poorly maintained electrical equipment
• Contact with underground cables
• Work on mains electricity supplies
• Work on live or dead electrical supplies
• Use of electrical equipment in wet or flammable atmospheres

Question 5

Control measures for electricial equipment

Answer 5

• Selecting equipment suitable fo rthe electrical system it will become part of. The job it will do and the environment in which it will operate
• Using the equipment accordingto manufacturers recommendations and notexceeding the electrical strengh and capability of the equipment
• Considering the hazardous environments the equipment may be used in ( i.e. extreme weather and temperature, natural hazards, contact with corrosive or flammable substances).
• Considering foreseeable mechanical damage

Question 6

A typical electrical permit to work has a ​number of elements, for example:

Answer 6

• Title and permit number
• Equipment, distribution board, circuit or job location, plant identification
• Description and nature of the electrical work to be carried out
• Hazards identified and precautions necessary
• Protective equipment and PPE required
• Authorisation that its safe to work
• Date time and duration of permit
• Identification of employees in control of the work
• Permit acceptance by those doing the work
• Considerations for extending the terms of the permit
• Returning to service on completion of the work
• Cancellation certifuing that testinghas been carried out an dthe plant is satifactorily re-comissioned

Question 7

Requirements for temporary electrical supplies

Answer 7

Temporary electrical supplies and equipment for use on construction sites should withstand the conditions of the site, be designed and manufactured to suitable standards, have flexibility in application for repeated use on various contracts, be easy to transport and store, be robust and resist damage, have lockabel switches and means of safe isolation

Question 8

Advantages and limitations of protective systems

Answer 8

• Fuses - a weak link in the system
• Circuit breaker - a mechanical swicth which automatically open when the circuit is overloaded
• Earthing - a low resistance path to earth for fault current
• Isolation - cutting the power
• residual current devices - Sensitive an dfacst acting trip
• Double insulation - two layersof insulation separating people from conductors

Question 9

Use of competent persons

Answer 9

Legislation requires that work on electrical systems and equipment, such as inspection an dtesting is carried out by competent persons

Question 10

Safe systems of work

Answer 10

No live work should be carried out unless:

• Its unreasonable for the equipment to be dead; and
• Its reasonable for the work to take place on or near the live conductors; and
• suitable precautons have been taken to preven injury

Safe isolation

Locating of buried services

Question 11

First-Aid treament for electric shock and burns

Answer 11

• Break the current between the victim and the source, isolate the power or separate teh victim from source with non-conductive material
• Call for ambulance
• If not breathing apply CPR
• For burns place a sterile dressing or pad of clean non fluffy material oe rthe burn, secure with bandage or tape
• Do not apply water or any lotions or ointment

Question 12

Control measures for working near overhead power lines

Answer 12

• Can work be avoided or done elsewhere
• If not workers must be informed
• Exact distances can be obtained but generally they are
  
  • ​15m of overhead lines suspended from steel towers
  • 9m of overhead lines suspended from wooden poles

If work involved requires workers to undertak etasks closer to the overhead lines than general safe distance states then addiitonal controls should be put in plaace

• Make the lines dead
• Erect barriers
• Permits to work

A risk assessment should be carried out