The electrical system is an apparatus that carries electricity in the building in question, it is composed of several elements:

the ducts, the meter, the electric cables, the earthing system, the junction boxes and the automatic differential switch.

 

There are two main categories of electrical systems, civil installations and industrial plants.

The former are used in private homes and places of public access such as schools and hospitals; the latter are used in work and production areas and are often used to move and automate "machines" in industries.

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Elettromeccanica 3C carries out all the phases of construction of electrical systems, from the technical design, implementation and testing of an electrical system are the rules of the Italian Electrotechnical Committee (CEI) to put it in order.

The low voltage electrical systems supplied by an electro-commercial organization must include an earthing system (TT system) as it is necessary for protection against indirect contacts.

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In electrical systems, faults or malfunctions can work.

The three main anomalous situations in which an electrical system can be found are:

short circuit: problem due to an insulation fault, which damages the equipment and indirectly damages people;
electrical leakage: a problem due to an insulation defect, which damages people;
overload: problem due to incorrect dimensioning of the conductors or too high costs (sound system), which deteriorates the equipment and can lead, over time, to short circuits and dispersions;
overvoltage: a problem due to lightning or another unwanted physical effect (sound system), which damaged the equipment.

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To prevent these events from causing damage to people or things, special protective equipment must be installed. Below are the descriptions and the usefulness of the main devices.

circuit breaker: it is a device for the protection of the system, which integrates both a magnetic protection for short-circuits and a thermal protection for overloads;
differential switch (popularly and erroneously known as "life-saving"): it is a device for the protection of people, which protects against electrical losses;
differential magnetothermal switch: it is a device for the protection of installation and people, which integrates all three magnetic, thermal and differential protections;
fuse: it is a device for protection against overcurrents, in domestic systems it is used almost exclusively for the protection of small users such as power supply units for intercom systems or bell transformers, in industrial environments it is commonly used in protecting motors against short circuits; it must be replaced every time it intervenes;
unloader: it is a device for the protection of the plant, which protects from overvoltages.
motor protection switch: it is a magnetothermal switch specific for the protection of motors against overloads and short circuits, with adjustable thermal trip threshold, often it is replaced by a thermal switch for motors combined with fuses.
Furthermore, in order for the residual current circuit breakers to function properly they must be coordinated with an earthing system, but their use is essential (as well as mandatory) even in systems that do not have them.