This FAQ page endeavours to answer the most common questions. Much
of the information on this web page has been summarised to make it
suitable for a wide audience. It's not meant to replace the authorities when concerning the law or electricity professionals you should contact whenever you encounter any serious electricity safety problems.
Which is safer, Alternating Current (AC), or Direct Current (DC)?
Alternating
Current (AC) and Direct Current (DC) have slightly different effects on
the human body, but both are dangerous above a certain voltage. The
risk of injury changes according to the frequency of the AC, and it is
common for DC to have an AC component (called ripple). Someone with
special equipment can measure this, but the effect on a particular
person is very difficult to predict as it depends upon a large number
of factors. As a consequence you should always avoid contact with high
voltage electrical conductors, regardless of the type of electrical
current they are carrying.
Everyone gets a ‘belt’ from electricity every now and then, don’t they?
No,
not if they are careful and follow the simple rules to securely isolate
electrical equipment, and check it is dead before they start work. If
you have received an electric shock but were not injured, then you are
lucky. Next time a slight change in events may lead to a very different
result. No one is immune to an injury from electricity.
How do I know if my electrical equipment is safe?
You
can find out if your electrical equipment is safe by carrying
out suitable checks, such as inspection and/or testing. The level
of inspection and/or testing should depend upon the risks. A simple visual inspection is
likely to be sufficient for equipment used in a clean dry environment.
In addition, equipment that is more likely to become damaged or is
operated in a harsh environment, is likely to require more
demanding electrical tests.
Checks should be
carried out often enough that there is little chance the equipment will
become unsafe before the next check. It is good practice to make a
decision on how often each piece of equipment should be checked, write
down the decision, make sure the check is carried out, and write
down the results. You should change how often you carry
out checks according to the number and severity of faults found.
The
best way to find out if specialised equipment is safe, is to have
it inspected and tested by a person with specific
competence on the type of equipment. This may be the original
manufacturer or his authorised service and repair agent. A
reputable servicing company that deals with the type of equipment
should also be competent to check its safety.
How do I know if my electrical installation is safe?
The
best way to find out if your electrical installation is safe is to have
it inspected and tested by a person who has the competence to do so,
such as an approved
electrical contractor. These can be found in the Yellow Pages.
How do I know if someone is competent to do electrical work?
A
person can demonstrate competence to perform electrical work if he or
she has successfully completed an assessed training course that has
included the type of work being considered, run by an accredited
training organisation, and has been able to demonstrate an ability to
understand electrical theory and put this into practice.
A
successfully completed electrical apprenticeship, with some post
apprenticeship experience is a good way of demonstrating competence for
general electrical work. More specialised work such as maintenance of
high voltage switchgear or control system modification is almost
certainly likely to require additional training and experience.
Can I do my own electrical work?
You
can do your own electrical work if you are competent to do so. Simple
tasks such as wiring a plug are within the grasp of many people, but
more complex tasks such as modifying an electrical installation may not
be.
Those
who wish to undertake electrical testing work would normally be
expected to have more knowledge and to be able to demonstrate
competence through the successful completion of a suitable training
course.
More complex electrical tasks such as motor repair
or maintenance of radio frequency heating equipment should only be
carried out by someone who has been trained to do them.
When should I use a residual current device?
It
is advisable to use a residual current device (RCD) (or ground fault circuit interrupter (GFCI)) whenever possible
but particularly in wet or damp locations such as outdoors. An RCD
rated at no more than 30mA limits the energy in a particular type of
electric shock and can save your life. However, an RCD cannot protect
you from every type of electric shock, so you should still make sure
that circuits are securely isolated before you work on them.
It
is best to use an RCD that is incorporated into the switchboard of your
installation. This means that all circuits fed from that RCD are
protected by the RCD. An RCD that is incorporated into an ordinary
mains socket, or plugged into it, will protect anything that is
attached to that socket, but it is possible that equipment may be
plugged into another, unprotected, socket.
RCDs should be
regularly tested by pressing the ‘test’ button, and by making sure that
the RCD trips. Faulty or inoperative RCDs should be removed from use.
RCDs rated above 30mA provide very limited protection against harm from an electric shock.
If you are using electrical equipment in particularly harsh conditions it is worth selecting lower voltage equipment powered by a transformer with an output centre tapped to
earth, or powered by a battery.
How often should I test my electrical equipment?
Electrical equipment should be visually checked to
spot early signs of damage or deterioration. Equipment should be
more thoroughly tested by a competent person often enough that there is
little chance that the equipment will become dangerous between tests.
Equipment that is used in a harsh environment should be tested more
frequently than equipment that is less likely to become damaged or
unsafe.
It is good practice to assess how often equipment
being used for work purposes should be tested, write down your
findings, make sure the testing is carried out, and write down the
results of the tests.
How often should I get my electrical installation tested?
Electrical
installations should be tested often enough that there is little chance
of deterioration leading to danger. Any part of an installation that
has become obviously defective between tests should be de-energised
until the fault can be fixed.
You should have your electrical installation inspected and tested by a person who has the competence to do so, such as an approved electrical contractor. These can be found in the Yellow Pages.
Who should I talk to about electrical safety?
In
the first instance a competent electrical contractor should be able to
give advice on electrical safety, and should also be able to direct you
to a suitable electrical engineer for advice about specialist areas.
When should I report an electrical accident?
In general, an electrical accident is reportable if:
- the person dies as a result of their injuries, OR
- the person suffers a major injury, OR
- a person receives an electric shock or burn
where the person loses consciousness, or requires resuscitation, or
other hospital treatment, OR
- plant or equipment came into contact with overhead power lines, OR
- there is an electrical short circuit or overload that causes a fire or explosion.
What should I do if I think someone is working unsafely?
If
you think someone is working unsafely you should ask him or her to stop
immediately and tell a manager.
What should I do to avoid danger from underground cables or wires?
Be prepared to spend a little time locating underground services using signs, maps, and locating devices.
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How do I work safely near overhead lines?
It can be difficult to identify the voltage of overhead lines so you should always assume overhead lines are dangerous when planning work near them.
What should I do if I touch an overhead power line?
Your local electricity distribution company can
generally supply stickers describing emergency procedures and
containing contact numbers that can be stuck in the cabs of vehicles
likely to be used near overhead power lines.
What voltages are dangerous?
A
wide range of voltages can be dangerous for different reasons. A very
low voltage (such as that produced by a single torch battery) can
produce a spark powerful enough to ignite an explosive atmosphere.
Batteries (such as those in motor vehicles) can also overheat or
explode if they are shorted.
If a person comes into contact
with a voltage above about 50 volts, they can receive a range of
injuries including those directly resulting from the electrical shock
(stopped breathing, heart, etc), and indirect effects resulting from
loss of control (such as falling from a height or coming into contact
with moving machinery). The chance of being injured by an electric
shock increases where it is damp or where there is a lot of metalwork.
Electrical or thermal burns can also occur from the flow of electrical current or hot surfaces.
When is it safe to work on live electrical equipment?
It
is never absolutely safe to work on live electrical equipment. There
are few circumstances where it is necessary to work live, and this must
only be done after it has been determined that it is unreasonable for
the work to be done dead. Even if working live can be justified, many
precautions are needed to make sure that the risk is reduced ‘so far as
is reasonably practicable’.
How do I make my electrical equipment safe to work on?
You
can be reasonably sure that your electrical equipment is safe to work
on if all sources of energy (electrical, mechanical, gas, pneumatic,
hydraulic, pressure etc) have been securely isolated and any stored
energy has been released from the equipment. You should always follow
the procedure for doing this described in the instructions provided by
the manufacturer of the equipment, and any local safety rules. If you
cannot find the instructions, contact the manufacturer and get them to
send you instructions before you start work.
Equipment
containing dangerous chemicals or other substances may have to be
decontaminated before it is safe to work on. You should ask a competent
person what to do.
It is important that there is no chance
that a source of energy can be deliberately or inadvertently
re-connected to the equipment whilst it is being worked on. This can be
achieved by applying a lock to each isolation device, and the person
doing the maintenance should have all the keys to these locks in his or
her possession. Warning notices should be posted at the points of
isolation.
Who has the responsibility to make sure everyone works safely?
It
is the responsibility of everyone to make sure that work is safely
undertaken. Managers have a responsibility to provide the resources,
instruction and training necessary to enable their workers to work
safely and so that others are not endangered by the work activity.
Workers have a responsibility to make sure they keep themselves, and
others safe.
What should I do if I think I have seen an unsafe electrical installation or equipment?
If
you think you have an unsafe electrical installation you should first
warn everyone to stay away from it, and, if it is safe to do so, switch
it off. You should then contact a competent person such as an approved electrical contractor who will be able to advise you how to make your installation safe.
If
the installation you think is unsafe is not owned by you or under your
control, you should attempt to find out who does own it, and contact
them. Electrical distribution poles, pylons and equipment should have a
contact telephone number attached to them.
If you cannot find
out who owns or controls an electrical installation you think is
unsafe, you should contact your local authority.
The summerised material on this page is courtesy of Health & Safety Executive (HSE - UK) and subjet to Crown copyright protection (UK)
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