Electrical safety
Accidents involving electricity are generally caused by a combination of three factors:
• faulty electrical equipment
• unsafe work practices
• environmental factors, such as dampness or flooding of equipment or work areas where there are
live electrical conductors.
These three factors are controlled by providing effective electrical insulation, earthing, guarding or
enclosure, electrical protective devices, and safe working methods.
Regulation of electricity at work
The safety of workplace electrical systems and equipment is regulated by the 'Electricity at work
regulations 1989' (EAW), which set out general principles rather than specific requirements.
An electrical system includes the source, the equipment, and all the means of connection between
them. It is the assemblage of wiring conductors, distribution boards, connectors, switches and
equipment connected to a source of electrical energy - this could be mains or a local mobile or
temporary power generator.
Electrical safety is a specialist area requiring the advice and guidance of a competent electrical
engineer or electrician. However, the aim of this guidance is outline the general requirements,
hazards and safe working procedures for electrical systems.
The main purpose of EAW is to prevent danger from contact with live electrical parts by ensuring
that equipment is:
• constructed of suitable materials
• regularly and effectively maintained
• protected against adverse conditions (mechanical, electrical and environmental damage)
• correctly installed and used
• provided with suitable earthing and protective devices
• provided with suitable means for disconnecting and isolating the supply
• used in accordance with safe systems of work (instructions and training).
These specific duties are expanded by the more general duties under MHSW and PUWER for risk
assessments, policies, information, safe operation and use, etc.
The Electrical Equipment (Safety) Regulations 1994 are principally aimed at manufacturers and
importers and apply to electrical equipment designed for use with AC voltages between 50 and
1,000 volts, and DC voltages between 75 and 1,500 volts. The Regulations implement the ‘low
voltage directive’ (sic) and apply across both work-related and consumer electrical equipment.
From 1 January 2005 Part P of the Building Regulations 2000 (which deals with electrical safety in
new buildings in England and Wales) came into force. However the new provisions, requiring major
electrical work to be notified to the local authority building control officer, only apply to dwellings’
electrical installation.
Electrical equipment - testing and inspection
All electrical equipment requires periodic testing and inspection to ensure it is safe for continued
use.
Electrical testing criteria and procedures are set out in BS 7671: 2001, ‘Requirements for electrical
installations. IEE Wiring Regulations. Sixteenth edition’ and the IEE 'Guidance Note 3: testing and
inspecting'. These tests should be performed and certified by an accredited person or inspection
body. These are typically members of the National Inspection Council for Electrical Installation
Contracting (NICEIC), or the Electrical Contractors Association (ECA).
The NICEIC publishes a regularly-updated list of approved contractors which is searchable at this
website:
http://www.niceic.org.uk/nonapproved/roll.html
Fixed electrical installations
Fixed installations include:
• wiring systems (from incoming supply cables to wiring to outlet points and switches)
• electrical switch-gear (isolators, switch fuses, fuse boards, distribution boards, bus bars, etc)
• fixed electrical equipment (lighting, socket outlets, switches, space heating, water heating, etc).
Testing
Fixed installations should be tested and inspected as follows:
Type of installation
Maximum period in years
agricultural and horticultural premises
3
caravan sites
1 (legal requirement)
caravans
3
churches (over 5 years old)
1
churches (under 5 years old)
2
cinemas
1 (legal requirement)
commercial premises
5
educational establishments
5
emergency-lighting systems
3
fire-alarm systems
1
highway power supplies
6
hospitals
5
industrial premises
3
launderettes
1 (legal requirement)
leisure complexes
1
petrol filling stations
1 (legal requirement)
places of public entertainment
1
temporary installations
6 months
theatres, etc
1 (legal requirement)
Apart from the legal requirements under other specific legislation, the inspection and testing periods
are only recommendations. However, if an incident were to occur, an enforcement body would use
these recommendations as guidance in ascertaining that everything was done ‘as far as is
reasonably practicable’ to ensure the safety of the electrical system.
The tests on existing installations that are connected to a supply should be performed in the
following order:
• earth-electrode resistance
• correct polarity
• earth-fault loop impedance
• correct operation of residual-current devices (RCD)
• correct operation of switches and isolators.
Part of the testing procedure will require that circuits are isolated from the supply to allow testing of
the insulation resistance. This may be performed on selected areas or the entire installation,
dependant on the type of installation and the working environment.
Inspection
The inspection of fixed installations should look for signs of damage, wear, abuse or overload and
cover:
• condition and security of switchgear (fixings, covers, access panels, etc)
• condition, security and protection afforded to wiring systems (cables, trunking, conduits, etc)
• condition and security of fixed electrical equipment (lighting, socket outlets, switches, space
heating, water heating, etc)
• condition and security of electrical connections
• correct polarity of switching (no neutral switching unless part of a multi-pole switch)
• correct labelling and sizing of switchgear, switches, cables, etc
• correct ratings of protective devices (fuse rating correct for the load)
• security of fixing and correct size of protective earth conductors
• presence of diagrams, instructions, notices, warnings, etc
• provision of protective measures (insulating mats, removal or securing of trailing cables, correct
tools and equipment, etc).
Electrical safety of work equipment
Although there is no specific legal requirement for electrical testing of work equipment, electrical
safety is part of the employer’s duty under the ‘Provision and use of work equipment regulations
1992’ and EAW to supply and maintain equipment that is safe.
The electrical aspects of work equipment include:
• plant and equipment (air conditioning, heating, and ventilation systems, process equipment, lifts
and lifting equipment, etc)
• machinery (workshop, manufacturing, fabrication, etc)
• pumps and motors (water, sewerage, drainage, sumps in lift wells, etc)
• control systems (switches, selectors, indicators, alarms, etc).
Testing
Electrical testing should follow the same procedures as set out in BS 7671 (and above). The testing
may be more specific, as this allows the opportunity to check and verify correct functioning and
condition of control circuits. Testing of work equipment should be included as part of a routine
maintenance plan to monitor and check that the electrical safety of equipment has not been
degraded through use.
The NICEIC publishes a regularly-updated list of approved contractors which is searchable at this
website:
http://www.niceic.org.uk/nonapproved/roll.html
Inspection
Inspection is an important aspect of electrical and machinery safety (see chapter on Machinery
Safety) as it can detect problems before they become a hazard. Any suitably trained person can
perform simple visual inspections before they operate work equipment. This will usually detect the
majority of defects, although a more detailed internal inspection will be require to be carried out by
a competent electrician periodically. Typical points to look for are:
• missing or damaged covers
• damaged trailing cables and leads
• damaged block motor cowls
• security of controls and switches (firmly fixed)
• signs of overheating or overload (burning or arcing)
• security of cables and switchgear (isolators, switches, conduits, etc).
Any defect should be reported immediately and the equipment should be electrically isolated until a
competent electrician performs suitable repairs.
Hazards of electricity and electrical equipment
Electricity poses a threat to life and property, and the hazards include:
• burns - these arise in three ways: by direct heating of the body tissues, leading to a very serious
injury that takes a long time to heal; by flash or arc radiation, caused by high temperatures near the
body due to flash-over and arcing; by thermal contact with hot conductors
arcing may start fires, or explosions in atmospheres that contain flammable gases or combustible
dust. Defective electrical equipment is a major cause of fires
• shocks - electric shock occurs when the body becomes part of the electric circuit. The current must
enter at one point in the body and leave at another. The severity of the shock depends on the
current, its path through the body, and the length of time the current flows. The effect ranges from a
mild tingling to immediate cardiac arrest. It should be noted that the range of current that causes
this range of effect is very small - less than 100mA (ie, one tenth of an amp). Muscular contraction
may prevent the victim from freeing himself or herself, thus prolonging the flow of current. It should
also be noted that low voltage does not imply low hazard.
Electrical equipment hazards
This section deals with specific hazards, including:
• live working - only allow when absolutely necessary, and only by competent engineers
• arc welders - risk of welding current flowing through other equipment, making it ‘live’
• mobile generators - risk of electrical shock, fire, asphyxiation in confined spaces, energising circuits
thought to be disconnected from the mains supply
• overhead cables
• underground cables - buried underground or in trenches or ducts
• batteries and battery charging - shock, fire, explosion of gases generated during re-charging
• electrostatic charges.
Safe working with electrical equipment
Safe use of electrical equipment involves:
• using electrical tools and equipment in good repair
• ‘switching off’ before inspecting or making repairs
• use of circuit protection devices.
Workers should be trained in the purpose and procedure of these three principles, including use of
‘permit to work’ (lock-out) systems.
Legislation
The EAW Regulations require that safe systems of work be used when working with electrical
equipment. This includes procedures for working in a manner ‘so as to prevent danger’. Typically,
this will require an electrical system to be isolated and confirmed that it is not live before work
commences. However, there are many circumstances where there is a presence of electrical
energy during normal working conditions, and in these cases, a safe system of work will need to be
used to ensure safety.
Safe systems of work should be designed on the basis of a risk assessment to assess the hazards
and control measures. In particularly hazardous situations, permits to work may be required. Any
safe system of work has to be supported by inspection and testing, suitable training, information
and supervision to ensure the competence and safety of the workforce.
The following sections suggest procedures that should be adopted for specific hazardous
situations.
Live-working with electricity
Wherever possible live-working should be prohibited, but there are situations where it is necessary
or unavoidable (service, testing or maintenance work). This specialist area should only be
performed by competent electricians or engineers, and even then only under the following
circumstances:
• when it is not practicable to carry out the work with the conductors dead, for example during testing
• making the system dead would create other hazards, for example when dealing with continuouslyoperating processes
• suitable precautions are in place.
Safety precautions during live-working
Suitable safety precautions for live-working require:
• properly trained person competent to work on live equipment
• suitable tools and equipment - insulated tools, rubber mats, insulated shoes or boots and in certain
situations gloves and aprons
• suitable instruments and test probes
• suitable barriers or screens
• accompaniment of another person if their presence significantly reduces the risk of injury
• restriction of live-work to specific areas and the use of isolated power supplies and non-conducting
locations.
Special provision for emergencies and rescue and medical treatment (first aid, resuscitation etc)
must also be taken into account.
Portable and mobile electrical power generators
In general terms, it is advisable to use 115V ac generators, and where this is not possible the 240V
generator, should be connected to an electrical circuit using an earthing system installed by a
competent electrician.
Consideration should also be given to positioning and refuelling portable generators as there is a
risk of fire, explosion or asphyxiation in confined or poorly ventilated spaces - as well as excessive
noise levels.
Remember that connecting a mobile generator to a fixed electrical system is extremely hazardous
and under normal circumstances should not be permitted.
Guidance on the safe use of generators can be found in the Contractors Plant Hire Association
(CPA) safety instructions.
Overhead power cables
This hazard is present where there are:
• power distribution lines
• overhead supplies for railway systems
• overhead cranes powered from un-insulated conductors.
The most common operations leading to contact with overhead line are:
• handling long scaffold tubes
• handling long metal sheets
• handling long ladders
• operating cranes and other lifting plant
• raising the body or inclined container of tipper lorries
• using MEWPs and other access equipment.
No plant or equipment should approach cables suspended from steel towers closer than 15m
measured horizontally from the line of the cables, or 9m in the case of wooden pylons.
Where there are live overhead cables near a work activity, the supplier authority should be
informed and the system should be made dead wherever possible. If this is not practicable, suitable
provisions should be made to ensure safety (permits to work, fences, barriers, supervision).
Underground power cables
Serious injury from shock or burns is preventable if three basic steps are followed:
• gather information from plans, and position and layout of above-ground electrical equipment before
work starts
• use cable-locating devices, and mark the cable's location on the ground with spray paint or similar
• follow safe digging practices: use of trial holes; using spades and shovels rather than powered tools
and mechanical excavators close to services; digging alongside and then horizontally rather than
over services; making dead electrical services buried in concrete before breaking it away.
Ensure that there is a readily accessible plan of known underground gas and electric services on
the site. This information is likely to be needed quickly in the event of emergency repairs to water
supply or drainage services.
Safe use of accumulators and batteries
The hazards associated with lead-acid batteries include:
• potential for electrocution at all times, as batteries are always live
• generation of hydrogen and oxygen from vented cells, leading to risk of explosion: there should be
a strict prohibition of smoking
• the corrosive nature of sulphuric acid, especially hazardous to the eyes
• lead is a chronic toxin.
BS 6133: 1995, ‘Code of practice for safe operation of lead-acid stationary batteries’ offers informal
guidance on all aspects of the safe use and disposal of lead-acid batteries (accumulators) including
the buildings and rooms in which they may be housed. BS 6132:1983 covers nickel, cadmium etc
batteries.
Rooms containing vented batteries must be ventilated to ensure that the concentration of hydrogen
does not approach 4% v/v. BS 6133 gives a formula to calculate the rate of evolution of hydrogen,
and recommends around six air changes per hour in rooms or cubicles containing batteries. Care
should be taken to ensure that the ventilation equipment is not an ignition hazard for the potentially
explosive atmosphere.
Electrostatic charge
Friction of materials or substances can build up very-high electrostatic charges (‘static electricity’)
with the potential to ignite flammable or explosive substances. Electrostatic charges can also
damage static-sensitive devices such as computer controls, etc.
Static electricity control measures include:
• earth-bonding - connecting all metal or conductive surfaces to earth. This is also required for
general electrical safety when earth-bonding gas pipes, water-supply pipes and metal baths, etc
• the use of earthed conductive materials - pipework, conveyors, conductive mats, clothing and hand
and leg straps
• ionisers - to neutralise electrostatic charges
• in static-sensitive areas - prohibiting the wearing of man made fibres.
At a more general level, maintenance of an atmospheric humidity level at around 50% will help
prevent build-up of static electricity.
Circuit-protection devices for electrical safety
These devices include fuses, circuit breakers, circuit breakers for equipment (CBE), earth-leakage
circuit breakers (ELCB) and residual-current devices (RCD). The aim of these devices is to protect:
• humans from the effects of electric shock (ELCBs and RCDs only)
• equipment from excessive electrical current
• against fire risks.
The selection and application of these devices requires specialist knowledge, however there are
simple guidelines that can be followed:
• test ELCBs and RCDs daily by pressing the test button - the mechanisms are prone to sticking,
thus negating the protection
• ensure appliances are fitted with the appropriate fuse - only use the correct fuse rating and fuse
materials.
Preventing deaths and injuries from lightning strikes
When organising or taking part in outdoor activities (especially those involving large crowds), be
aware of the weather forecast. Because lightning often precedes rain, preparations to avoid
potential lightning strikes should begin before the rain starts. The danger of lightning strike is high
when the interval between lightning and thunder is less than 30 seconds.
When thunder is heard, seek shelter inside the nearest building or enclosed vehicle (such as a car).
If shelter is not available, avoid trees or tall objects because electricity may be conducted from that
object to other nearby objects or persons.
Avoid high ground, water, open spaces, and metal objects (eg, golf clubs, umbrellas, fences, and
tools).
When indoors, turn off appliances and electronic devices and remain inside until the storm passes.
Key terms on electrical safety
Electrical hazard
The potential to cause a fatal electrical shock, or electrical burn.
This is generally taken to involve a system capable of delivering at least 50V ac or 120V dc to any
person. Electrical hazards also include the potential to ignite explosive atmospheres.
Health and safety legislation does not set voltage limits on electrical hazards, and uses the terms
'hazard' and 'danger' interchangeably
Circuit protection devices
A device that isolates the system in the event of a fault to earth. The speed at which the device
operates determines its effectiveness in saving life or damage to property.
The purpose of earth-leakage circuit breakers (ELCBs), circuit breakers for equipment (CBE) and
residual-current devices (RCDs) is to automatically shut-off the current in the event of a short
circuit, overload, or fault with the earth connection. The devices can protect life, as they act very
quickly.
Fuses and circuit breakers are intended to protect property and equipment, and prevent fires due to
overload and over-heating. They play little part in preventing electrical shock.
Isolation
A means of removing the electrical energy from the equipment and securely preventing accidental
reconnection. It implies more than simply ‘switching off’, but complete disconnection from the
electricity supply.
Electrical equipment
Anything used or intended to be used in connection with electrical energy. This includes
appliances, generators, batteries, transformers, rectifiers, cables, conductors, meters and control
equipment.
The definition is very wide in scope, covering battery-operated equipment to high-tension electricity
distribution equipment as used by the national grid.
Electrical system
An assembly in which electrical equipment is connected to a source of electrical energy. A system
includes the source, the equipment, and the means of connection between them
Portable equipment
Electrical equipment connected to a fixed installation or generator, which is either hand-held or
hand-operated which is likely to be moved while connected to the supply: extension leads, electric
kettles, grinders, portable hand lamps, electric drills, floor cleaners, electric pressure cleaners, etc.
Competent electrical contractor
In legal terms, this is a person with sufficient technical knowledge, experience and skills to be able
to carry out a specific task and prevent danger or injury.
The National Inspection Council for Electrical Installation Contracting (NICEIC) is an independent
safety organisation, and is accredited by UKAS for the assessment of electrical work within the
scope of BS 7671: 2001, ‘Requirements for electrical installations. IEE Wiring Regulations.
Sixteenth edition’, other than in hazardous areas.
Electrical contractors enrolled with the NICEIC may display the new NICEIC Registration Mark on
their business stationery, company literature, advertising etc. Such contractors must comply with
the NICEIC Rules, in particular the requirement that their work complies with BS 7671. However,
the Council’s requirements are no more than the minimum that any competent electrical contractor
should meet.
Other sources of guidance on identifying a competent electrical contractor include the Electrical
Contractors’ Association’s (ECA) publication ‘A Client Guide to the Certification and Procurement of
Electrical Installations’. The ECA operates a similar accredited assessment scheme, the
Electrotechnical Assessment Scheme. This is a certification scheme to assess contractors and their
qualified supervisors in aspects of electrical installation activities.