Repsol YPF

Many of us are used to handling electronic devices without having the slightest idea of how they work inside. As if by magic, we simply plug them in and expect them to meet our needs. However, the increasing complexity of such devices should not dissuade us from understanding certain basic concepts which can be highly useful to us. 

Any large electrical appliance with metallic casing such as fridges, ovens, washing machines, etc, is liable to suffer the odd defect in the insulation of its electric circuit which will allow the electricity to travel into the exterior. If we were to touch it, particularly with bare feet or when walking on a wet floor (given that electric current tends to flow through the path of least resistance), we could become an electricity conductor, facilitating the path between the appliance and the floor and this would certainly not be very pleasant. It could even endanger our life. 

As such, since 1973, the law stipulates that all new buildings must have an earth connection. This is a part of the electric circuit, the function of which is to prevent cases of electrocution. Thanks to them, instead of being passed through our body, the electricity “would escape” through the earth connection in a much safer manner.  

How they work

In new installations, the earth connection is compulsory for all circuits, including light circuits. They are easy to spot in plug sockets, they consist of two small metal clips located on the sides. These clips are connected to a cable which the law requires to be yellow and green, in order to make it easy to identify. 

All of these yellow and green cables which come from plug sockets lead to the same place; it is a kind of electricity drain which takes the shape of a two-metre metal bar, which is driven into the ground at the bottom of the building. This piece is usually called the ground electrode and has an average thickness of six centimetres when it is made of steel, or of barely fourteen millimetres, when it is made of copper. This is the most common electricity installation. Nevertheless, there are others where instead of electrodes, copper or zincified iron plates or metal meshing are used, or a copper cable is simply buried (without insulation).  

If this is the system installed in buildings, high-tension cables from the distribution network also have their own system. In this case, the earth wire is located at the top of the pylons and connected to their structure which has a similar earth connection to that described above. That way it can play a dual role: not only does it protect people from an accidental electric shock but, since it is higher than the conductors it also serves as a lightning conductor, as such the lightning strikes which can occur during storms are diverted straight to the earth and do not interfere with the electricity supply.

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