Power transmission systems in most buildings are made according to the old model - without grounding. Modern household appliances that operate without a ground loop can fail in the event of any malfunctions. Homeowners usually carry out the installation of grounding in the house themselves, thereby ensuring electrical safety.
Purpose of grounding
The main task of grounding is to reduce the mains voltage to zero in the event of a current leakage. The reason for this may be touching live parts, damage to the insulation of the wiring. An additional function of grounding is to create and maintain optimal conditions for the operation of household electrical appliances.
Some devices require not only a grounded outlet, but also a direct connection to a ground bar. For this purpose, special clamps are used.
For example, there is a special terminal on the case of microwave ovensfor grounding. In the absence of grounding, touching the microwave oven can cause a slight but unpleasant electric shock. This is eliminated only by installing a protective earth. The situation is similar with most other household appliances.
Installation of grounding in a private house is an equally important procedure, especially if the building is wooden. The existing ground loop allows you to protect buildings from lightning strikes and the fire provoked by it. This is especially important in rural areas, where houses can quickly burn out in a short time. Simultaneously with grounding, a lightning rod is most often equipped.
Grounding arrangement rules
When natural grounding elements do not meet the requirements, artificial grounding systems are used. Natural elements can be steel pipes located in the ground, metal structures of buildings, artesian wells and many others.
It is forbidden to use oil pipelines, gas pipelines and gasoline pipelines as natural grounding conductors.
The optimal material for installing portable grounding with your own hands is a metal corner 50 x 50 millimeters 3 meters long. To install such elements, a trench is dug 0.7 meters deep, while about 10 centimeters of segments should remain above the bottom. A steel bar with a diameter of 10-16 millimeters or a steel strip is welded to the protruding part.
Ground loop resistance in electrical installations up to 1000 voltsshould be 4 ohms, no more. Resistance for installations over 1000 volts should not exceed 0.5 ohms.
Types of grounding and features
There are six grounding systems, but only two are used in private homes: TN-C-S and TT. The first type is more popular, since it has a dead-earthed neutral. Conducting the neutral N and the PE bus is carried out by one PEN wire to the entrance to the building, after which the grounding is bred into several separate branches.
Protective functions in such a circuit are carried out by electric machines, while there is no need to install protective shutdown devices. Such a scheme has its drawback: if the PEN conductor is damaged at a distance between the house and the substation, a phase voltage appears on the ground bus in the house. It is impossible to turn off the voltage with any protection, and therefore it is necessary to install a mechanical protection of the PEN conductor and a backup ground at a distance of every 200 meters.
Electrical networks in small towns and villages do not meet the necessary requirements, and therefore use the TT scheme. The best option for using this scheme is for individual buildings with a dirt floor, since there is a certain risk of touching the ground and ground at once, which is dangerous when using the TN-C-S scheme.
The difference is that the "ground" is used as a shield from an individual ground, and not from a substation. This system is more resistant todamage to the conductor and requires the installation of a special residual current device. For this reason, such a scheme is called a backup.
Ground installation
Grounding devices are classified into two types, which differ in properties and installation method. The first type is represented by a pin modular design with several electrodes, the second is created from rolled metal. The main differences between the varieties are the recessed parts, while the conductors and the overhead part are completely similar.
Commercially purchased grounding kits have certain advantages:
- Components are designed by specialists in accordance with all standards and requirements and manufactured at the factory;
- Practically no excavation or welding needed;
- You can go deep into the ground while maintaining the minimum resistance of the entire device.
Main disadvantage is too high cost
A set purchased from a retail chain has its own advantages:
- Sold as a set, the elements of the set are designed by specialists in compliance with all the requirements of the rules, manufactured on factory equipment.
- No welding required, and almost no earthwork needed.
- It makes it possible to go deep into the ground to a considerable depth with low resistance of the entire grounding device.
Among the shortcomings of the factory design, you cannote the high cost of the set.
Tools and materials
For the manufacture of a home-made ground electrode, galvanized rolled metal must be used - a pipe, a corner or a bar.
Ready-made ground electrodes are made of carved copper-plated pins connected by brass couplings. The connection of the pin and the earth wire is made with a stainless steel clamp and a special paste. Grounding conductors must not be painted or lubricated.
When choosing the section of rolled products, the effect of corrosion is taken into account, as a result of which the section is reduced. Minimum rolled sections:
- For galvanized rod - 6 mm;
- For rectangular products - 48 mm2;
- For a metal bar - 10 mm.
The pins are connected to each other with a corner, a strip or a wire. With their help, grounding is brought to the electrical panel. For connecting bars, the dimensions are:
- Bar diameter - 5 mm;
- Size of rectangular profile - 24mm2.
The cross section of the phase wire must be greater than the cross section of the ground wire in the room. Such conductors are subject to certain requirements affecting the diameter of the cores:
- Aluminum without insulation - 6mm;
- Copper without insulation - 4mm;
- Copper insulated - 1.5mm;
- Aluminum insulated - 2.5mm.
Grounding conductors are connected using grounding bars made of electrotechnical bronze. All parts of the shieldaccording to the TT scheme, they are attached to the wall of the box.
Installation of grounding on a self-made overhead line is carried out with the help of a sledgehammer, with which the ground electrode is driven into the ground. Driving in factory parts is done with a jackhammer. In both ways of installing grounding, it is desirable to use a stepladder. Manual welding is used for welding rolled ferrous metal.
Earthworks
There is a certain procedure for installing grounding. The first stage is earthworks. Grounding conductors are placed at a distance of 1 meter from the foundation of the building. The minimum distance between pins is 1.2 meters. The best option is to use pins 3 meters long and create a triangle with 3 meters sides.
After a trench is dug 0.8 meters deep. The optimal trench width is 0.7 meters: it is enough for convenient welding of conductors.
Electrode preparation
The sharpening of the electrode is carried out with the help of a grinder. If used rolled metal is used, it is cleaned of corrosion and old coating. Factory-made pins are equipped with sharp heads, which are screwed on and smeared at the junction with a special paste.
Electrode recess
Deployment of electrodes into the ground is carried out by driving them with a sledgehammer. To facilitate the work, it is better to use a scaffold or stepladder. If the metal of the electrodes is too soft, then the blowsapplied through special wooden bars. It is not necessary to hammer the pins to the end: about 10-20 centimeters should remain above the ground, which are used to connect to the circuit.
Clogging of factory electrodes is carried out with a jackhammer. After the pin is deepened, a coupling and an additional ground electrode are screwed onto it. The process is repeated several times until the required depth is reached.
Electrode connection
Between themselves, the pins are combined with a strip of 40x4 mm. Rolled ferrous metal is welded, because the bolts quickly corrode, which leads to an increase in the resistance of the overall circuit. Welds must be of high quality.
From the assembled circuit, grounding is carried out in a strip to the house and attached to the foundation. The wire from the shield is connected to a bolt welded to the edge of the strip.
The fastening clamp is installed on the last electrode, after which the wire is fixed. The clamp is sealed with a special tape.
Backfilling the trench
It is best to fill the grounding trench with homogeneous dense soil.
Shop-bought single-prong grounding devices come with plastic inspection wells.
Conducting grounding in the shield
The switchboard is installed on the wall of the building, and the installation site must be protected from moisture. Cables are led through the wall using special pipe sleeves. Connecting the wire to the installed onthe shield body of the bus is carried out using a bolted connection.
After installation, grounding is checked with a multimeter. The number of electrodes increases with resistance exceeding 4 ohms. Ground wires in yellow insulation are connected to the appropriate connector of the ground bus. When connecting various devices - lamps, open-mount sockets with grounding, and others - the yellow wires are also connected to the corresponding terminals. For example, on sockets, a similar terminal is located in the center. Flush-mounted sockets with grounding are considered the safest - they are used to connect refrigerators, gas stoves and other household appliances.
