No one can see electricity but it is in use almost constantly every day, coming into contact with just a tiny amount can prove lethal. Our own bodies produce very small micro amps of electricity, these are overwhelmed if we come into contact with a live electrical source. The heart can be stopped, muscle spasms can result and a person may not be able to let go of the cable. Other associated injuries include falls and being thrown e.g. off a ladder. The severity of injuries will depend on the current flow, the part of the body exposed and moisture content etc.
Unlike manual handling, the actual number of electrical accidents is small. However, the severity of injury through such accidents is very much higher than with other causes.
Electricity is supplied in two forms referred to as ‘alternating’ and ‘direct’. Alternating is the most hazardous form of supply normally encountered in the workplace. This is usually supplied at a voltage of either 220 or 240 volts (single phase supply) or 415 volts (three phase supply) both of which have the potential to be fatal. Three phase supply is normally encountered in industrial settings or larger commercial operations where heavy duty equipment is present or there are extensive electrical circuits in operation. Direct current comes from batteries.
Electricity or an electrical current is a flow of electric charge along a wire. The more charges that are passing along the wire, the larger the current.
Alternating Current (AC)
This type of electricity we get from plugs in the wall. In an alternating current all of the electric charges switch their direction of flow back and forth.
An alternating current is produced by an electric generator. This consists of a magnet and a loop of wire which rotates in the magnetic field of the magnet. As the wire rotates in the magnetic field, the changing strength of the magnetic field through the wire produces a force which drives the electric charges around the wire. The force initially generates an electric current in one direction along the wire. Then as the loop rotates through 180 degrees the force reverses to give an electric current in the opposite direction along the wire. Every time the loop rotates through 180 degrees the direction of the force, and therefore the current, changes.
Direct Current (DC)
This is the type of electricity that we get from batteries. In direct current all of the electric charges move in one direction. A direct current is produced so we have to look again at the electric charges in an atom. A direct current is caused by an imbalance between these electric charges.
If the two terminals of the battery are connected together electrons are able to pass along the wire from the negative terminal to the positive terminal to attempt to balance the electrical charge. As the electrons move through the wire they loose energy and this energy turns into heat. Since the energy that the electrons have comes from chemical energy in the electrolyte eventually the chemical energy runs out and the battery becomes flat. This is a direct current.
PORTABLE ELECTRICAL APPLIANCES
There is no legal requirement for PAT testing, despite the advertising material you may find targeted at businesses. The Electricity at Work Regulations require electrical systems to be constructed and maintained to avoid danger. Carrying out tests and inspections of portable appliances and the fixed installation can assist in preventing danger but PAT testing alone will not avoid danger. Equally there are some categories of equipment which even the HSE’s own guidance recommends that PAT testing is not required – ever!
The first step in ensuring the safe use of portable equipment is to ensure that it is correctly identified and a suitable inventory is undertaken. Anything with a plug attached is deemed portable even if it does not physically move around the workplace.
Typical problems with the use of portable appliances include:-
• Damaged cables
• Cables pulled too tight so they pull the wires from the connectors in the plug
• Damaged plugs
• Wrong fuse fitted
• No fuse used but a nail or piece of foil etc used instead
• Blocked air vents
• Items left on all the time
• Equipment unsuitable for the work environment e.g. 240v tool used outside in the wet.
• Damaged casing
• Damaged controls
• Exposed wiring
• Unsuitable connectors / insulation e.g. with sellotape
What are the different types of portable electrical equipment?
Portable electrical equipment can be categorised into four types:
Class 1 or earthed equipment: This equipment will have conductive materials such as a metal case that could become ‘live’ if there was a fault in the equipment. An example would be a metal kettle or metal-cased drill. In order to provide protection, the conductive parts are ‘earthed’ by means of an earth wire.
Class 2 or double-insulated equipment: This equipment has two layers of protective insulation and is therefore unlikely to become live. This equipment does not require an earth wire.
Class 3 equipment: The protection against electric shock relies on the voltage not exceeding 50 V ac (safety extra-low voltage). This equipment is more specialised and requires special outlets and transformers.
Battery-operated equipment: This is generally used where there is an increased danger of electric shock or where portability is important. Such equipment is not normally subject to inspection or testing for electrical safety.
Factors to consider in selection of equipment
When purchasing new equipment, an assessment of the use to which it will be put should be made. Equipment should meet the standards laid down by the British Electrotechnical Approvals Board (BEAB) or have a
CE mark. Before purchasing equipment consideration should be given to:
• any future maintenance requirements;
• foreseeable work locations and conditions;
• the most appropriate voltage for the equipment;
• the likely risk that the equipment will pose while in use.
Before new electrical equipment is put into use for the first time, checks should be made to ensure that:
• the plug, flex and casing are in good condition;
• the correct rating of fuse has been fitted;
• persons have received adequate training and instruction on its use;
• the equipment has been entered into the inspection and maintenance cycle;
• an adequate risk assessment has been carried out;
• a safe system of work has been established and documented if necessary.