The grounding of the electrical system: what it is, how it works and what the cable is for

THE’grounding It is the set of elements that make a electrical connection between the land and all parts of the system that could accidentally tension in faulty conditions, although they are not in their normal operation. Each electrical system must be – law (Presidential Decree no. 462 of 22 October 2001) – Equipped with an grounding system. Basically, we are talking about a protection system which allows you to limit any damage and dangers (also and above all to humans), guaranteeing the safety of the whole electrical system and the people who use it.

What is the ground and how it works

Let’s imagine a simple electrical system in which there is at least one device that needs, for its operation, of electric current in the circle. In case of broken downfor example for non -insulation of a simple cable, the device in question it could become a “mass“: that is, the same could go live and become a source of Transfer of electric current For those who come into contact with it. If this occurs through a human being, exposure and duration of the contact themselves can become dangerous to health and safety! Under these conditions, the earth system intervenes in order to Create a preferential lane of current migration, removing the danger.

We can therefore say that the earth system represents an area of ​​the circuit in which, in the event of a breakdown, current circulation preferentially Compared to the remaining part in contact with the inhaled element. This is then downloaded actually on the groundthat is, in the ground. Migration to the ground takes place because the same offers the less resistance possible to the passage of electricity and therefore it naturally encourages this movement, which it would happen anyway – even without land system – but through a path that could compromise the safety of the electrical system and of those who use it.

THEplant must be sized in order to obtain this migration current in a “controlled” way. For example, the type of soil in which we go to “close” this circuit can show different electrical resistance values ​​as its composition/type vary. In some cases, it may be necessary to work on multiple grafting points on the ground or apply other strategies to optimize the yield. Without grounding, the current can accumulate in the appliances, overheat them and cause fires. In addition, overvoltages can seriously damage computers, appliances and other electronic devices. The greatest risk, however, is for people: a live device can transmit dangerous electric shocks, with even serious consequences.

What is made up of an grounding system

Mainly, the land system consists of three elements:

• Protective conductorsor all the electrical cables that connect the possible masses present with the land system;
• The elements disperseror all the elements that disperse electric current in the ground. We are talking about elements of galvanized steel or copper (in some cases, it is also possible to use the armor cages of the foundation structures), directly fixtures in the ground and connected to the electrical system through the protective conductors;
• The switch differentialvulgarly called savevitathat is, that electrical instrument that automatically blocks the flow of current at the entrance in case of failure. The differential is nothing more than a good accountant which, meticulously makes an account of How much current enters the plant and how much comes out. If this algebraic sum is not zero, it means that part of the current is going elsewhere: if this happens, the differential is activated and within a few milliseconds the electrical system deactivates, interrupting the current passage.

In general, The grounding system is not 100% effective. This means that from the element in tension only a part – although substantial – of the current will pass towards the ground, while there will always be a minimal part that will tend to to get to the ground for another road. Nevertheless, this quantity is small and practically such as not to cause damage to people in the exposure period Until the activation of the life -saving. For this reason, theland system is effective only if all parts of the system arewhich is why the same requires periodic checks to avoid the presence of malfunctions, which unfortunately could be latent until the actual need for its operation!

How to recognize the ground

In an electrical system, the grounding cable is conventionally indicated through the color of his insulation/protection sheath, which is yellow-green. This cable, which collects all the branches from the whole system (therefore from all masses), in the final part of its path, it creates physical contact with the dispersor fixed in the ground, usually protected within a cockpit: it is precisely at this point that the passage of the electric current from the system to the ground is carried out. In some cases, the arrival “On the ground” of the plant is also indicated by A specific signrepresenting the symbol indicated in the following figure.