Grounding consists in ensuring the electrical masses have the same potential as the earth so that they are dispersed in the ground without hitting man.

Each electrical system, in fact, is crossed in all its parts by an electric current with different potential compared to the ground and if these live elements are inadvertently touched, the electric discharge can cross the body and electrocute it.

Generally all parts of the system are well protected and isolated so the danger is minimal, but there are some elements, such as household appliances, which are normally not live, but which, in the event of a fault, can create a very dangerous situation . Hence the need to connect every part of a building or apartment to a grounding system in accordance with the law or to an earth rod placed in the ground.
What is meant by electrical grounding?

With the term “Grounding” in electrical engineering we mean the set of all those operations, and the related systems, which are necessary to bring all the points of a specific metal structure (belonging or not to an electrical system) to the same electrical potential (voltage) of the ground which is 0 volts.
What is this system for?

The earthing system in synergy sometimes with other safety devices such as the differential switch or circuit breaker, performs multiple functions aimed at ensuring maximum safety of an electrical system.
Protects people from electrocution.

Electrocution that generally occurs by contact with metal parts that should not be in tension and that, following accidents, are found to be so (in these cases we speak of indirect contact).

By connecting all the metal structures (in an appropriate manner that we will examine below) to the earth, their potential will be pruned to 0 and in the event of accidental contact with a live element this will be discharged to the ground. This will prevent people who accidentally touch these objects from being electrocuted.

To clarify what has been said, we report a concrete example. The situation is typical of a household appliance which is normally at 0 potential, but which, due to deterioration of the insulating sheath of a conductor, becomes live. The presence of earthing, in this situation, will favor the intervention of the RCD (if it is installed in the system as it should) due to the circulation of a leakage current to earth.

Even in the case in which unfortunately the life-saving differential is not present, the earthing equally protects people from possible electrocutions. In this case, in fact, the one who touches the carcass under tension will form a resistance with his body which will result in parallel with the resistance to ground of the system much lower than that of the body.

Now, since in a parallel loop subjected to tension the currents passing through the two resistances are divided inversely proportional to their respective resistances, the majority of the current will flow to the ground through the earth resistance. Thus causing certainly minor damage to the victim.
Protects from danger of shock during work.

By connecting a section of an electrical system under maintenance and on which work must be carried out to earth and therefore to potential 0, the operators who will go to work to restore the system are protected from any electrical accidents.
Protects against the accumulation of electrostatic charges.

In particular structures that are isolated from the ground, grounding is carried out to avoid the accumulation of electrostatic charges (passage of electrical charges between different materials).

An example is represented by the bodywork of automobiles which on dry days is electrostatically charged by friction with air particles. The electrostatic charges are distributed on the metal surface of the car and will discharge to the ground giving us a feeling of shock when with our feet on the ground we touch the car door. To avoid this problem, the body is grounded (which is isolated from the tires) with special strips that, connected to the frame, rub on the road.
The legislation makes it mandatory.

The current legislation on the subject makes it mandatory to earth the systems.

The law requires that all private and condominium buildings be equipped with an earthing system. All the systems and metal parts of the building, from the electrical system to the pipes, from the hydraulic system to the heating and photovoltaic system must be grounded, so that the whole building is made safe even with respect to any lightning that might invest it.

Protective grounding is also mandatory for temporary structures. It is therefore imperative to carry out grounding even in scaffolding that is installed in construction to renovate or repair buildings. Said scaffolding has an armature consisting of metal carpentry which could accidentally come into contact with sources of electromotive forces used to power electrical machinery or simply to illuminate the scaffolding itself.

The grounding of the scaffolding provides for the connection of all the nodes of the metal structure by means of cables of suitable section to a line that will disperse in a special pit of which we will provide a more detailed description below.
How an earthing system is made.

In these brief notes on the practical implementation of an earthing system we will refer only to the type of protection which is the one we are most familiar with, as the one that is present in our apartments.

An earthing system of a building is created by connecting to a single line, all the branch cables coming from the junction boxes, which connect the wires coming from all the earth poles of the sockets of each apartment in the building, as well as any metallic mass contained in the houses (chandeliers, windows, gates, water and gas pipes, television antennas, etc.).

The branches coming from the boxes of each building connected will end in a condominium earth leakage pit.

The spinning of the plant, according to what is established by the CEI or the Italian Electrotechnical Committee recognized by the European Community and which deals with the regulatory activities of the sector, must be zebra-striped in yellow-green colors.

The cockpit is made of concrete, raised from the ground and can be opened for inspection. Between its walls it encloses a portion of earth in which a metal stake is planted, made of a material of difficult corrosion (puntazza), longer than a meter and with a star or cylindrical section, on whose protruding head (20 cm from the ground) is firmly bolted the ground wire.

The realization of the connections of the ground system described above means that all the metal structures of the building are at the same potential as the ground, ie at 0 volts. Naturally, the resistances to earth must be rigidly lower than the tolerance of the differential switch or circuit breaker so that it can intervene in the event of current leakage.

Finally, it is important to explicitly clarify that the sizing of such a system is not a simple work and generally cannot be a do-it-yourself job, unless you have specific skills. In fact, it requires a project by an engineer who will also have the task of certifying the plant. Certification which by law is mandatory.
If the sizing of the system is not carried out in a workmanlike manner, serious problems could occur. In fact, the ground connection of the water and heating system (radiators and boiler) could cause potential differences between pipes and appliances in the case of atmospheric discharges affecting the home, putting the inhabitants’ safety at serious risk.

The earthing systems as well as the leakage well require continuous monitoring with measurement of the relative resistances. For this reason the junction boxes are made in such a way as to make the various branches sectionable in order to make it possible to measure the respective resistances. In the same way, the leakage well must be inspectable to measure the resistance to earth.

Naturally, what has been described for residential buildings is carried out, with different systems, also in industrial installations, photovoltaic systems, public lighting systems and so on.
Is it possible to modify a domestic earthing system with the DIY?

As already mentioned, it is good practice not to modify an earthing system which, due to the complexity of its operation, must be designed in a global way by appropriately balancing the resistances of its various sections.

However, there may be some simple events in which you can also intervene on your own without necessarily resorting to the advice of a technician.

The most common case is that of having to move a socket to power a new appliance or for a different arrangement of furniture.

How to behave in such situations? The answer is quite simple.

Just start from the nearest socket and carry from this a new line that will feed the new socket. Line that will be composed as the starting one by three distinct wires: phase, neutral and earth.
How do they recognize each other?

The earth is the one connected to the central pole of the socket and is carried by a yellow-green wire.

The phase is the one connected to one of the external poles, usually carried by a brown wire. It is easily recognizable because it is the one that makes the phase finder bulb light up when, with the meter active, it is touched with the metal tip of this.

The neutral is generally the blue wire always connected to an external pole of the socket and which does not light up the phase detector.

The important thing of the whole operation, which obviously must be done with the voltage off, is to connect the new line to the three poles of the old one in the correct order, i.e. phase with phase, earth with earth and neutral with neutral in the same order in the poles of the new socket.

Another fundamental precaution is to use wires with a section equal to that of the previous ones.