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Electrical Safety Inspection...
Electrical Appliance Testing or PAT Testing as it is sometimes referred to, is an important part of any Health & Safety Policy. If your working environment has any appliances with a plug attached, then these are classed as Portable Appliances. To minimise the risk of a potential fire or the risk of an electric shock to either an employee or the general public, or for insurance purposes, it is important to have these appliances safety tested to promote a safe working environment.
Electrical equipment includes:
· Portable hand held and stationary appliances, designed for connection to the low voltage (240v) supply by a flexible cord (including the cord). This includes for example, portable power tools, machine tools that are not hard wired, soldering irons, welding machines, sewing machines, kitchen appliances such as fridges, microwaves, ovens etc. This also includes items brought to school by staff for use in the school. Items such as toasters, irons, fan heaters, fans etc.
· Extension leads and power boards.
· Residual Current Devices (RCDs) of all types. An RCD is a mechanical switch device designed to make, carry or break currents under normal service conditions. It opens the contacts when the residual current rises too high.
Electrical safety is dependent on sufficient electrical insulation between 'electrically-live' parts and the user, and also on the proper 'earthing' of appliances.
When the insulation of an appliance breaks down, the earth connection has to be good enough to allow a 'protective device' to interrupt the electrical supply to the appliance.
Common insulation failures occur in cords by way of exposure, hardening and cracking of the individual conductor insulation (two conductors for 'double insulated' equipment, three for others), and through moisture and dirt build-up.
An electrical safety test using an appliance tester is done by plugging it into the tester which in turn is plugged in to the electrical supply.
The insulation and earthing tests, as well as others, are than carried out. The two essential tests, as required by the Australian Standard AS/NZS 3760:2001 are:
· Earth bond test (other than for double-insulated apparatus).
· Insulation test.
Double-insulated appliances are recognised by a label indication in words and/or with a symbol consisting of a smaller square within a square.
They are normally furnished with a two-pin connector, but that in itself should not be taken as an indication of double-insulation status.
Other tests that can be performed are:
· Earth leakage test.
· Operational test.
· Extension lead test.
The earth leakage test, although not mandated for appliance testing, can be useful.
Earth leakage is, in electrically-safe equipment, a small current that flows through the insulation back to earth. It is normally too small to cause even the slightest of 'tickles' when touching the metallic parts of an appliance.
In Australia, the use of so-called 'earth leakage breakers' in electrical installations is now a standard requirement.
RCDs (Residual Current Devices--or earth leakage breakers) are situated on switchboards and distribution boards. These devices interrupt the electrical supply to the appliance when the leakage current exceeds the 'tripping level' of the breaker.
Where RCDs are part of a portable board, for example in outdoor situations, the RCD should be checked daily or prior to the use of an appliance, in order to comply with the above-mentioned Australian Standards.
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