Grounding and grounding of electrical installations
Grounding of electrical installations- navmisne electrical installations in the housing from the grounding outbuildings.
Grounding of electrical installations of two types: zahisne groundingі zeroing, yakі may be one and the same recognition - to protect people
in the presence of an electric strum, as if they had bumped into the body of the electrical installation, or other parts, as if they had stumbled under the pressure.
Zahisne grounding- navmisne electrical installation of a part of the electrical installation from a grounding outbuilding with a method of electrical safety. It is intended for the protection of people from the dotik to the electrical installation housing or other parts that have stooped under the pressure. Chim lower opіr grounding outbuilding, Tim better. To get ahead of grounding, you need to buy sockets with a grounding contact.
In case of breakdown of insulation between the phase and the body of the electrical installation, the body can be under voltage. At the same time, a person bumped into the hull - a strum, to pass through the people, not to become unsafe, to that the main part of the leak was along the zahisnoy grounding, as if it were already a low opir. The grounding is made up of grounding and grounding conductors.
Є two types of grounding – naturalі piece.
Before the natural grounding one can see metal constructions of budives, above ground from the ground.
As a piece of grounding, vicorous steel pipes, shearers or a tuft, with a length of not less than 2.5 m, hammered to the ground and welded one by one with steel smugs or welded with a dart. Like grounding conductors, which connect the grounding device with grounding devices, ring steel or mid-rails, or weld them to the car bodies, or bolt them with bolts. Zahisny grounding is supported by metal cases of electrical machines, transformers, shields, wardrobe.
If it is not grounded, it will significantly reduce the voltage, but you can eat a person. Tse tim, that the conductors of grounding, the grounding himself and the earth may be a deaky opir. In case of gradual insulation, the strum runs through the body of the electrical installation, grounding and farther along the ground to the neutral of the transformer, vibrating a voltage drop on the lower support, even if it is less than 220 V, but it can be sensible for people. To change the voltage, it is necessary to get used to lowering the grounding support under the ground, for example, to increase the number of piece grounding machines.
Zeroing- navmisne electrically connected parts of the electrical installation, which normally do not lie under the voltage of a deafly grounded neutral with a zero drotom. It should be done before the flickering of a phase on the body of the electrical installation is transformed into a short flicker of the phase with a neutral wire. The strum at the time of the fault is significantly larger, the lower one is due to the sound grounding. Shvidke that outside inclusion of a poor possession is the main recognition of nullity.
Separate zero working explorerі zero zahisny explorer.
The zero working conductor is used for the life of electrical installations and can, however, be connected with other wires, insulation and sufficient passage for the passage of a working stream.
Zero winding conductor to serve for the creation of a short-hour strumu of a short twirl for spratsovuvannya zahistu that swidkogo switch-on
Poshkogenoy electrical installations in the area of life. In the capacity of a zero-fire dart, there can be steel pipes, electric wires and zero dart, which can not be beaten by vimikachiv.
Significance of the earthing system
Grounding systems are distributed according to the schemes of grounding and the number of zero workers and other conductors.
The first letter of the identified grounding system indicates the nature of the grounding of life:
T - non-intermediate neutralization of the neutral dzherel life from the earth.
I - mustache strumovidny parts of іzolovanі vіd zemlі.
Another letter in the knowledge of the grounding system indicates the nature of the grounding in the critical conductive parts of the electrical installation:
T - non-intermediate connection between the conductive parts of the electrical installation being from the ground, regardless of the nature of the connection between the dzherel and the ground.
N - non-intermediate connection between the critical conductive parts of the electrical installation and the grounding point of the lifeline.
Letters that go through the rice for N indicate the way to add a zero wind and zero working conductor:
C - functions of zero protection and zero working conductors are provided by one fire conductor PEN.
S - functions of the zero-tolerant PE and zero-working N conductors are provided by separate conductors. budіvl old budіvl, recognized for the placement of computer equipment and telecommunications, it is necessary to ensure the transition from the TN-C system to the TN-S (TN-C-S) system.
The TN-C-S system is typical for yards that are being reconstructed, in some zero working and future conductors are combined only in part of the circuit, at the input of an electrical installation (for example, in an apartment panel). At the introductory extension of the electrical installation of confusion, there is a null and working conductor PEN of divisions into a null conductor PE and a zero working conductor N. At the same time, a null conductor PE is connected with the mouth of the electrical installation. The TN-C-S system is promising for our country, which allows you to secure a high level of electrical safety for a remarkably small power supply.
The TN-S system has a zero working and a zero supply conductors, and the laying is OK. From the substations come five residential cables. All conductors of the electrical installation are labeled as zero conductor PE. Such a scheme includes a return stream at the conductor PЄ, which reduces the risk of vindication of electromagnetic shifts. A good option for minimizing the plant is a transformer substation (TP), which allows you to provide a minimum conductor length for the introduction of electrical cables to the head clamp. The TN-S system does not require re-grounding for the presence of a substation, the shards at this substation are the main grounding device. Such a system is expanded in Europe.
4. TT grounding system
The TT system has a transformer substation without a middle connection between the strum-conducting elements and the ground. All conductive parts of the electrical installation will have an uninterrupted connection from the ground through the grounding device, electrically independent of the grounding conductor of the neutral of the transformer substation.
5. IT grounding system
In the IT system, the neutral of the lifeline is insulated from the ground or grounded through an attachment or an extension, which is a great support, and the conductive parts are grounded. The strum of the coil on the hull or on the ground will be low and not vpline on the mind of the robot and the received possession. Such a system is vikoristovuetsya, as a rule, in electrical installations budіvel, to which vysuvayutsya pіmogi schodo bezpeka.
Loop grounding scheme
1. Grounding
2. Grounding conductors
3. Grounded possession
4. Virobnicha wake up.
An example of a grounding booth
1. Water heater
2. Grounding officer
3. Metal pipes
plumbing, sewerage, gas
4. Main ground bus
5. Natural grounding (reinforcement for the foundation of the building)
Come in for a zahistu from the electric shock
For the defense of people in the event of an electric shock, zastosovuyut zahisnі zasobi - gum mittens, tools from insulated handles,
gumovі boti, gumovі kilimki, zapobіzhnі posters.
Wire insulation control
In order to prevent unfortunate accidents from an electric jet attack, it is necessary to control the insulation of the wires of electrical installations. The wire insulation mill is re-tested at new installations, after reconstruction, modernization, interruption at robots.
Preventive control of the insulation of wires should be carried out at least 1 time in 3 years. Opir іzolyatsії wires are measured with megaohmmeters for a rated voltage of 1000 on strips with the fuses removed and when the strum receivers are switched on between the skin phase wire and the neutral working wire and between the skin two wires. Opir іzolyatsії is guilty but not less than 0.5 Mohm.
