We know that it is still extremely common that there is no electrical grounding scheme in the electrical installations of homes, which is a serious mistake made by electricians and homeowners, and the main reasons for not making a grounding system is to “save” money or for lack of knowledge. According to the NBR-5410 standard, it is mandatory to use the grounding scheme in the properties and for this reason, we will show you how to make a grounding scheme for your property and explain a little about grounding schemes.
What is an electrical grounding?
Electrical grounding has the function of leaving all electrical installations and electrical and electronic equipment on the same electrical potential so that the potential difference between grounding and equipment is as close to zero as possible. One of the functions of grounding is to drain leakage loads, so that when the machines and electrical equipment are being operated and when carrying out maintenance, the operator or professional in the area does not submit to the electrical discharges of this equipment, either by electric current. leak, which is going to the ground or by electrostatic discharge.
Types of electrical ground
There are several types of grounding such as TN, TN-C, TN-S, TN-CS, TT and IT, different letters are used to classify the electrical grounding schemes.
The first letter indicates the food situation in relation to the land:
- T = A point directly grounded, for example, ground rods.
- I = Isolation of all living parts from the earth or grounding of a point through an impedance.
The second letter indicates the situation of the masses of the electrical installation in relation to the earth:
- T = Masses directly grounded, regardless of the eventual grounding of a supply point.
- N = Masses connected to the grounded supply point (in alternating current, the grounded point is normally the neutral point).
Other letters (if any), arrangement of the neutral conductor and the protective conductor:
- S = Neutral and protective functions provided by different conductors.
- C = Neutral and protection functions combined in a single conductor (PEN conductor).
TN grounding scheme
The TN scheme has a directly grounded point, the masses are connected to the grounded feeding point, so that the grounded feeding point is usually the neutral point.
The TN scheme has three variations of the grounding scheme, for example, TN-C, TN-S and TN-CS, each variation will depend on the arrangement of the neutral conductor and the protective conductor (PE).
TN-S diagram, the neutral conductor and the protective conductor are separate.
TN-CS diagram, part of which the neutral and protection functions are combined in a single conductor.
TN-C diagram, in which the neutral and protection functions are combined in a single conductor, in the entire diagram (PEN).
TT earthing scheme
This scheme is considered the most effective among grounding schemes because each electrical and electronic equipment has its own grounding rod. The neutral is grounded separately from the electrical and electronic equipment and continues to the equipment.
IT grounding scheme
The IT grounding scheme is similar to the TT, however the electrical and electronic equipment is grounded through an impedance with a high value, all living parts are isolated from the earth and grounded through an impedance.
- How to make TN-CS electrical grounding scheme?
To make a ground according to the NBR-5410 standard, it is necessary to hire an electrician who is knowledgeable in the area, as it is necessary a wide knowledge to make an effective electrical ground and with appropriate tools such as the earth meter that is used to measure resistance grounding. The help of a trained professional is of utmost importance, to inform which is the best earthing scheme for your residence, how many earthing rods should be used for earthing and which electrical materials are needed to make earthing.
First step, choose a suitable location to install the grounding rod. After choosing the location where the ground rod will be installed, make a small excavation in the ground to insert the inspection box.
The grounding rod must be inserted into the ground, to do this mark the middle of the inspection box and then insert the rod into the ground up to the average height of the inspection box, leaving a surplus above the ground for connection of the protective conductor in the stem.
Make a trench from the inspection box to the wall where the utility meter passage box is located (if there is no conduit for the passage of the protective conductor, it is necessary to install new conduits), the trench must have the necessary depth to fit the PVC conduit in the hole in the wall of the inspection box, after installing the conduit in the ditch, cover it with earth.
Then pass the protective conductor through the conduit coming from the passage box to the rod, for this we use the grounding rod connector for the connection between the protective conductor and the rod.
After performing all this process, turn off the meter breaker to connect the ground to the neutral that is in the passage box next to the meter, remove the existing insulation, strip the protective conductor and make the connection to the neutral in and then isolate again.