Objective
- To ensure that systems which promote safe work practices for all electrical workers working on or in the vicinity of electricity are established.
- To ensure that work conducted on or around electrical conductors or equipment is only carried out by suitable trained and qualified personnel.
- Local Legislations and Regulations to be fully explained before commencing the activity.
Responsibilities
Business Owners, Managers and Supervisors
- Ensure that site specific risk assessments as required are carried out on the prescribed form. Records of the assessment shall be kept and placed on record.
- Ensure the requirements of the appropriate Legislation and Standards in your country, state or county are complied with and suitably qualified personnel perform all recording and reporting functions.
- Ensure that Contractors and/or Sub Contractors conducting work activities for or on your behalf comply with all Safe Work Practices and Procedures or have a safety system in place that meets or exceeds the requirements of your country, state or county.
- Ensure that only trained, qualified and competent people carry out work on electrical systems.
Workers
Workers must not do any electrical work except as:
- A qualified person being the current holder of an electrician’s license authorized to do that work in your local area; or a person who has been issued with a license to perform electrical work by your recognized Country, State or Territory Authority. The licensed person may also be known as an Electrician, Electrical Mechanic, Electrical Fitter or Electrical Worker depending on local legislation.
- A current holder of a restricted license authorizing its holder to do that work under supervision.
Definitions
Electrical Work
Work on electrical machines or instruments, on an electrical installation or on electrical appliances or equipment to which electricity is supplied or intended to be supplied at a nominal pressure exceeding 50 volts alternating current or 115 volts direct current whether or not the item on which the work is performed is part of, or is connected to or to be connected to, any distribution works or private generating plant and, where work is performed on any appliance, whether or not electricity is supplied or may be supplied there to through an electric plug socket or socket outlet.
Electrical Installing Work
Work of assembling and fixing in place, altering or adding to any electrical installation or maintaining, enhancing, repairing, removing, or, connecting to fixed wiring, any electrical equipment.
Electrical Installation
Includes all wiring, wiring enclosures, switch gear, control and protective gear, appliances and any other components permanently connected to or associated with the wiring and that is on premises to which electricity is or is intended to be supplied through distribution works and where electricity is supplied from a private generating plant includes that plant.
Electrical Fitting Work
Work of making, maintaining, repairing, altering, assembling, dismantling, connecting or testing electrical machines, electrical appliances, electrical instruments or other electrical equipment.
Electrical Equipment
Any wide range of fixed or semi-portable machinery requiring electrical energy for operations.
Electrical Appliances
Portable and semi-portable electrical devices from domestic appliances – Washing Machines, Toaster, Hair Dryer etc to electric portable tools.
General Facts
The following information relates to the consequences of coming in contact with an energized electrical source:
Electrical Shock and its Consequences
The severity of electrical shock depends on:
- Shock current taken by the victim.
- Time of contact with the live equipment.
- Path of current flow through the victim.
- Body resistance.
Shock current and its effect:
Various researches throughout the world have established the following figures as being factual:
- 1-3 milliamps – can be felt.
- 10-15 milliamps – hard to let go.
- 25-30 milliamps – chest muscles contract; unable to breathe.
- Above 50 milliamps – heart affected; flutters and does not pump (fibrillation)
- Above 5 amps – current paralyses nerve centers in heart, is clamped, and resumes pumping when current removed.
Note: A current as low as 20 milliamps can cause death.
Time for fibrillation to occur:
The time of contact before fibrillation occurs is related to the cardiac cycle of the heart and is as shown below:
| Milliamps |
Time in Seconds for Fibrillation to Occur |
| 25 |
5.75 |
| 30 |
4.0 |
| 50 |
1.45 |
| 100 |
0.36 |
| 190 |
0.1 |
These figures were established by an international body of experts at a Geneva meeting in 1961 and still relevant.
Path of current flow in body:
The most critical path of current flow through the body is where the heart is in the path of this flow.
NOTES:
The above figures are for contact from hand to hand, hand to food or head to foot, where the current path passes the heart and respiratory centers. Contact from foot to foot or other areas not involving the heart is less severe.
Body resistance:
It has been found from post mortem research that for 50 cycles the resistance figures are constant under the skin through fat and tissue, at about 600 OHMS. The resistance of the skin varies from person to person, and depends on the moisture and condition of the skin.
It can be as high as 2,000 OHMS, and the accepted minimum figure is 500 OHMS from hand to hand or for a body in a conducting fluid about 200 OHMS. For instance, on a 250 volt system the minimum current taken by a person would be 480 milliamps. This is well above the acceptable limit.
NOTES:
The above figures have been taken from persons with a normal heart. Any heart abnormality would considerably increase the effects as noted above.
Voltage
The voltages generally encountered on projects are as described in countries standards and are listed below:
Extra Low Voltage – Not exceeding 50 volts AC or 120 volts ripple-free DC
Low Voltage – Exceeding ELV but not exceeding 1000 volts AC or 1500 volts DC.
High Voltage – Exceeding LV (not covered in this e-book)
NOTES:
Work on “live” conductors at these voltages must be taken very seriously. There have been more electrical fatalities throughout the World from low voltage shocks than from contact with high voltage conductors.
While not especially dangerous to the average person, voltages below 50 volts can also cause shocks and be hazardous to a susceptible person. To attempt to control these risks, some jurisdictions in your country, state or county have recently introduced new legislation, which places more stringent requirements for working on low voltage. Local Legislations and Regulations must be referred to at all times.
Safe Operating Procedures (only trained, qualified and competent people carry out work on electrical systems)
General Rules
These general rules apply to working on energized Low Voltage apparatus and conductors.
- ALL CONDUCTORS AND APPARATUS SHALL BE REGARDED AS “LIVE” UNTIL PROVED “DEENERGISED (DEAD)”. Special note shall be made to ensure all neutral cables and earth cables are proven “DEAD”. Note: Only approved test equipment shall be used for this purpose.
- Work on live equipment shall not to be carried out unless allowed under local legislative or contractual arrangements.
- Confirm permission to isolate.
- Fit a Danger – “Do Not Operate” Tag.
- Cover and insulate adjacent live apparatus.
- Check test instruments before and after use on a known voltage source or approved instrument test device.
- Start work only when authorized to do so.
- All extension leads and power tools shall be used through either fixed or portable residual current devices.
- All electrical power tools/equipment and extension leads shall be tested and tagged with the current color coded tag or approved tag.
- Always use personal protective equipment and remember that PPE is the last control measure in the hierarchy of control. Always use PPE in conjunction with other protective devices i.e. insulating barriers etc.
