Power transmission systems in most of the buildings are made according to the old model - without grounding. Modern household appliances that operate without a grounding circuit can fail in the event of any malfunction. Owners of houses, as a rule, independently carry out the installation of grounding in the house, thereby ensuring electrical safety.
Grounding purpose
The main task of grounding is to reduce the network voltage to zero in the event of a current leak. The reason for this may be touching live parts, damage to the wiring insulation. An additional function of grounding is the creation and maintenance of optimal conditions for the operation of household electrical appliances.
Some devices require not only the installation of an outlet with grounding, but also direct connection to the grounding bus. For this purpose, special clamps are used.
For example, on the case of microwave ovens there is a special terminal for grounding. In the absence of grounding, touching the microwave may result in a slight but unpleasant electric shock. This is only eliminated by installing a protective ground. A similar situation with most other household appliances.
Installing grounding in a private house is an equally important procedure, especially if the building is wooden. The existing grounding circuit allows you to protect buildings from lightning and fire caused by it. This is especially important in rural areas, where houses can quickly burn out in a short time. At the same time as grounding, they most often equip a lightning rod.
Grounding Rules
If the natural grounding elements do not meet the requirements, artificial grounding systems are used. Natural elements may include water-based steel pipes in the ground, metal structures of buildings, artesian wells, and many others.
It is forbidden to use oil pipelines, gas pipelines and gas 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 0.7 meters deep is dug, while about 10 centimeters of segments should remain above the bottom. A steel rod with a diameter of 10-16 millimeters or a steel strip is welded to the protruding part.
The resistance of the grounding circuit in electrical installations up to 1000 volts should 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 in private homes only two are used: TN-CS and TT. The first type is more popular, since it has a grounded neutral. The neutral N and PE bus are carried out with one PEN wire before entering the building, after which grounding is routed into several separate branches.
The protective functions in this scheme are carried out by electric machines, while there is no need to install residual current circuit breakers. This circuit has its own drawback: when the PEN conductor is damaged at a distance between the house and the substation, phase voltage appears on the ground bus in the house. It is impossible to disconnect the voltage with any protection, and therefore it is necessary to install mechanical protection of the PEN conductor and redundant grounding at a distance of every 200 meters.
Electric networks in small towns and villages do not meet the necessary requirements, and therefore use the TT scheme. The best option for applying this scheme is for individual buildings with a dirt floor, since there is a certain risk of touching the soil and grounding at once, which is dangerous when using the TN-CS scheme.
The difference is that the "ground" is used as a shield from individual grounding, and not from a substation. Such a system is more resistant to damage to the conductor and requires the installation of a special protective shutdown device. For this reason, this scheme is called a backup.
Grounding installation
Grounding devices are classified into two types, which differ in properties and installation method. The first type is represented by a modular pin design with several electrodes, the second is created from rolled metal. The main differences between the varieties are in-depth details, while the conductors and the aboveground part are completely similar.
Earthing kits purchased from a distribution network have certain advantages:
- Accessories are developed by specialists in accordance with all standards and requirements and are manufactured on factory equipment;
- Virtually no need for earthwork and welding;
- You can go deep to a considerable depth in the ground while maintaining a minimum resistance of the entire device.
The main disadvantage is too high a cost.
The kit purchased in the distribution network has its advantages:
- It is sold as a set, elements of the set are developed by specialists in compliance with all the requirements of the rules, manufactured on factory equipment.
- No welding is required, and almost no earthwork is needed.
- It makes it possible to delve into the ground to a considerable depth with obtaining low resistance of the entire grounding device.
Among the shortcomings of the factory version, the high cost of the kit can be noted.
Tools and materials
For the manufacture of a home-made earthing switch, galvanized metal-roll must be used - a pipe, corner or bar.
Ready-made earthing switches are made of carved copper-plated pins connected by brass couplings. The connection of the pin and the ground wire is made using a stainless steel clamp and a special paste. Do not paint or grease the earthing switch.
When choosing a section of rolled products, the effect of corrosion is taken into account, as a result of which the section decreases. Minimum sections of hire:
- For galvanized wire - 6 mm;
- For rectangular steel - 48 mm 2 ;
- For a metal bar - 10 mm.
The pins are connected together by a corner, strip or wire. With their help, grounding is brought up to the electrical panel. For connecting rental sizes are:
- Bar diameter - 5 mm;
- The size of the rectangular profile is 24 mm 2 .
The cross-section of the phase wire must be greater than the cross-section of the grounding wire in the room. Certain requirements are imposed on such conductors affecting the diameter of the cores:
- Aluminum without insulation - 6 mm;
- Copper without insulation - 4 mm;
- Insulated copper - 1.5 mm;
- Aluminum insulated - 2.5 mm.
Grounding conductors are connected using grounding buses made of electrical bronze. All parts of the shield according to the TT scheme are attached to the box wall.
The installation of grounding on a home-made overhead line is carried out using a sledgehammer, with which the ground electrode is driven into the ground. Driving factory parts occurs with a jackhammer. In both methods of installing grounding, it is desirable to use a stepladder. Manual welding is used for welding ferrous metal.
Excavation
There is a certain procedure for installing grounding. The first step is excavation. Grounding conductors are placed at a distance of 1 meter from the foundation of the building. The minimum distance between the pins is 1.2 meters. The best option is to use pins 3 meters long and create a triangle from them with three-meter sides.
After digging a trench 0.8 meters deep. The optimal width of the trench is 0.7 meters: it is enough for convenient welding of conductors.
Electrode preparation
The sharpening of the electrode is carried out using a grinder. If used metal is used, it is cleaned of corrosion and old coatings. The factory-made pins are equipped with sharp heads that are wound and smeared at the junction with a special paste.
Electrode deepening
The electrodes are buried in the ground by clogging 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 blows are applied through special wooden bars. It is not necessary to hammer pins to the end: about 10-20 centimeters that are used to connect to the circuit should remain above the ground.
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 desired depth is reached.
Electrode connection
The pins are joined together by a strip of 40x4 mm. Ferrous metal is welded because the bolts quickly corrode, which leads to an increase in the resistance of the general circuit. Welds must be of high quality.
From the assembled circuit, grounding is carried out by a strip to the house and is attached to the foundation. The wire from the shield is connected to a bolt welded to the edge of the strip.
The mounting clamp is installed on the last electrode, after which the wire is fixed. The clamp is sealed with a special tape.
Backfill trench
It is best to fill up the grounding trench with a homogeneous dense soil.
The one-pin grounding devices purchased at the store are equipped with plastic wells, allowing for audit.
Grounding the shield
The switchboard is installed on the wall of the building, and the installation site must be protected from moisture. Cables are routed through the wall using special pipe sleeves. The wire is connected to the bus mounted on the shield body 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 corresponding ground bus connector. When connecting various devices - lamps, sockets of an open installation with grounding and others - the yellow wires are also connected to the corresponding terminals. For example, on outlets, a similar terminal is located in the center. The most safe are considered sockets of a hidden installation with grounding - they are used to connect refrigerators, gas stoves and other household appliances.