• robertbrown07



There are a number of different types of electrical extension cables available, but most are susceptible to misuse or abuse. They can include multi-block adaptors, cable extensions with a single outlet, multi-socket extension leads and cable reels. Fixed electrical sockets are always preferable to use rather than the use of extensions.

Common Issues


The most common and dangerous problem with extension leads is to 'electrically overload' the extension. Electrical overloading of an extension cable occurs when several electrical appliances, each of which draw a significant amount of electrical current when in operation, are collectively plugged into a single multi-socket or multi-block adaptor electrical extension.

Moreover, electrical overloading of an extension can occur when one extension lead is plugged into a further extension lead and so on which is generally referred to as ‘daisy chaining’.

Given that an extension lead is ‘plugged’ into a power outlet ‘wall socket’ then this establishes that the extension lead has a maximum electrical current rating of 13 amps or 3kW, since the extension lead has a BS 1363 three-pin (rectangular) plug with an integral 13 ampere electrical fuse protection device.

Hence extension leads should not be utilised with high electrical current drawing appliances e.g. portable heaters, kettles, microwaves, etc. These items should be plugged directly into a power outlet ‘wall socket’.

Damage to Cables

Electrical extension cables are often damaged by people walking on the cable, passing the cable through doors and windows or due to contact with moving furniture provoking abrasion of the plastic outer coating of the cable and eventually the copper core of the cable exposing the subsequent risk of electrical shock.

Moisture Exposure

If an electrical extension is used in an open-air environment then a suitable electrical protection device such as a residual current device (RCD) should be used in conjunction with the extension cable and should be fitted where the extension is plugged into the power outlet ‘wall socket’. To minimise the risk of electric shock injury, it is advisable that the RCD has a tripping current of not more than 30 milliamps (mA). And further that the RCD must be tested prior to use of the extension by using the ‘test’ button located to the front of the RCD.

Dr Robert E Brown practices as a professional expert witness and forensic engineer in the fields of electrical, electronic and control engineering.




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