Poole Radio Society offers the following information ONLY to
help candidates obtain their Foundation Licence. It is the responsibility
of readers of this site to properly understand and assess the risks and
precautions needed when working with electricity, electrical equipment and
wiring.
Electrical Risks
·
High voltages carry a risk of electrocution (they can kill).
· High
currents carry a risk of over heating and fire.
Such things as Watches, Rings, Necklaces, Wires are all able
to conduct electricity and potential sources of danger, not only to you if they
touch high voltages, but also even on very low voltages if they pass large
amounts of current.
Safety Earth
· Mains
powered equipment should have a safety earth fitted.
· If
a fault develops in the equipment, it is possible that live parts (at mains
voltage of 230 Volts) could become connected to the metal case. This
poses a risk of electrocution unless the metal case is earthed. If the
case is properly earthed and a live part comes into contact with it, then the
fuse will blow.
· Double
insulated equipment does not have metal cases, and have extra insulation in
their construction to prevent faults causing accessible metalwork (e.g.
headphone sockets) becoming live.
· Many
houses have PME (Protective Multiple Earth) installations. There is a
risk that the house earth may rise above earth potential. Special
arrangements are therefore needed. You should check the earth
arrangements in your home, taking advice from your local electricity supply
company if necessary.
Fuses
· A
correct fuse must be fitted to all electrical equipment.
· The
main purpose of the fuse in the plug is to protect the mains lead and internal
wiring in the equipment. Low power devices will have a thin mains lead
that can overheat at currents below the protection of a larger value
fuse. Do not assume all faults are short circuits. It is possible
to have a fault which will not blow a large fuse (e.g. 13A) in adequate time or
at all, but which would overheat a 2A flex.
Working on Mains Equipment
· You
should only ever work on Mains-Powered equipment when it is fully disconnected
from the mains. (The mains plug is removed from the mains socket).
Wiring a Mains Plug
· Mains
plugs should only be worked on when they are completely disconnected from the
mains.
A 3-Pin Mains Plug is wired up as shown in the diagram
below: -
The Wire Colours |
|
Colour |
Description |
Brown
|
Live Wire – This is always the wire that is connected to one
end of the Fuse.
|
Blue
|
Neutral Wire.
|
Yellow / Green striped
|
Earth Wire. Not all equipment will have an Earth
Wire. If an Earth Wire is part of the equipment’s mains cable, then
this MUST be connected as shown
|
· It
is important to make a tidy job of fitting the mains plug.
· Whiskers
(odd strands of wire) must be avoided.
· The
cable grip must be fitted and the cable grip screws tightened.
Master Off Switch
A clearly marked switch to turn off all station equipment in
an emergency is the quickest way to cut the power to all equipment in the event
of an accident or suspected accident.
Accidents Involving Electricity
In the event of
an accident involving electricity, the first thing to do is to switch off the
power. The casualty must not be touched unless the power has been
switched off.
Rescuers are at risk of electrocution themselves unless they
know that the power is off. They won’t know how the casualty suffered
possible electrocution, so they don’t know what is “live”. It is easy to
rush up to casualty and risk touching them or moving them. If the
casualty is still in contact with a live wire, the rescuer will also become a
casualty.
Other Safety Considerations
Poole Radio Society offers the following information ONLY to
help candidates obtain their Foundation Licence. It is the responsibility
of readers of this site to properly understand and assess the risks and
precautions needed when carrying out amateur radio related activities.
Wires
· Do
not have wires trailing across floors
· People
may trip over them, and injure themselves in the fall.
· They
may drag equipment, possibly live equipment, off the bench or table, which can
then cause injury, and possibly exposes live wires.
· There
is also a risk of the insulation becoming frayed, resulting in a risk of
electrocution or fire.
Elevated wires and antennas
· Elevated
wires, feeders and antennas must be suitably located and secured.
· They
need to be clear of being walked into, resulting in direct injury, or being
pulled down, thereby causing injury.
·
They need to be properly fixed so that they don’t get blown down by the
wind and by a bird flying into them.
· They
should not be sited close to overhead power cables. If they should come
down (perhaps in a storm) they could come into contact with high voltages, with
a risk of electrocution of people nearby.
· Erecting
antennas is potentially hazardous. It is advisable to have someone to
help you. Workings on a ladder, raising heavy items, represent increased
risks. You should always have an adult present when undertaking
potentially risky activities. There should always be a second person
present to summon help if an accident does occur.
·
Antenna elements should not be touched when transmitting and should be
mounted to avoid accidental contact. This does not apply to low powered
hand-held equipment.
· Antennas
and feeders carrying r.f. can cause burns by arcing or by energy absorption in
tissue. This is possible even if the wires are insulated but
unscreened. Accidental contact by people and animals needs to be
considered.
· Particularly
high antennas may need special protection against lightening strikes.
Antennas should be disconnected from equipment when not in use.
Using Headphones
· Excessive
volume when using headphones can cause damage to hearing.
· The
volume should not be turned up too loudly.
· The
damage from excessive volume can cause damage over many years that cannot be
reversed.
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