Man of the 21st century has become so accustomed to electricity that he completely forgets about the danger that lurks in it. Modern electrical appliances increase it many times over. To always feel safe, you should ground your household appliances.
Grounding loop - how it works and what is the difference from grounding
In most old buildings, voltage is supplied to the house through two wires, of which one is phase and the other is neutral. A potential difference arises between them, which is called voltage, and it is usually 220 Volts. All electrical appliances are connected to the outlet using a two-pin plug. But modern devices have another contact on the plug, called “ground”.
IN an ordinary house with a two-wire system it is useless, and in modern apartments serves for grounding devices. Since 1997, all new buildings have used a three-wire system with an additional ground wire. In old private sector houses there are still two wires without grounding. But it’s not at all difficult to install it yourself, and then you can be confident in your own safety.
In some cases, a situation arises when the phase voltage shorts to the housing, and household appliance appears under tension dangerous person. Moreover, it is not necessary to touch the surface; it is enough to stand on a wet place near the boiler or washing machine. Particular danger comes from household appliances, which is simultaneously connected to the network and water supply.
The following equipment should be grounded:
- 1. A washing machine, which has a large electrical capacity of its own and in a damp room, even one grounded through a European socket can be pinched. Connected to a water supply made of metal pipes, it represents increased danger. The same applies to the boiler.
- 2. A microwave oven that uses ultra-high frequencies. If an outlet has poor contacts, it will begin to emit rays at levels that are hazardous to health. Many products have a special grounding point on the back.
- 3. Hobs, electric stoves, electric ovens. Have greater power, working conditions internal wiring extremely heavy, high probability of breakdown.
- 4. A personal computer whose power supply leaks a lot. This reduces productivity.
When the device is grounded, the moment a person touches it, he will not feel the shock. The purpose of grounding is to divert the current that penetrates the housing into the ground. That is why, when touching a faulty but grounded electrical appliance, the voltage on the housing is not dangerous to a person. It does not become the only current conductor through which it begins to flow into the earth layer.
Zeroing is also intended to prevent human injury. But it connects and works according to a different principle. If the device is energized, it turns off. Much depends on the shutdown devices that are used. These could be fuses or automatic device. In any case, they will protect the person.
For people who have a superficial understanding of electrical engineering, it is easier to make a ground loop, since its installation requires more skills of a mechanic and welder than an electrician.
Grounding elements - materials used
The grounding loop in a private house consists of a conductor and a ground electrode, which is located in the ground itself. For the grounding conductor, a current-carrying core is used, which connects the busbar on the panel to the grounding conductor. Its cross-section depends on the phase wire. If it has a cross-section of up to 16 mm 2 at the input, then the grounding cable must have the same cross-section or larger. At large sizes phase wire, the cross-section going to the ground loop can be half. The materials of both conductors must be the same.
From the top of the grounding conductors there is a metal connection to the shield, which grounds its body. A strong metal structure is formed, which is attached to the shield through a bolt, and to the rod by welding.
The ground electrode itself has an extremely simple design: horizontal conductors laid in the ground and vertical grounding electrodes. Russian and international requirements allow the use of steel, black or with various coatings, and copper - tinned, galvanized or uncoated. The rods must extend at least half a meter into the soil, which never freezes or dries out. To ensure that they are in constantly moist soil, their length should be 2–3 m.
Various shapes of elements are allowed: strip, rod, corner, pipe. Each material has limitations regarding minimum size. For example, a steel strip cannot be thinner than 4 mm, regardless of its width. Such conditions are dictated by the need to resist corrosion. Installation of steel parts is carried out by welding; the bolts are quickly destroyed.
Steel materials must meet the following requirements:
- rods for rods with a diameter of 16 mm and above:
- horizontal – at least 10 mm;
- steel pipes with a diameter of 32 mm and larger.
For reliable grounding, the cross-section of the material must constantly double. For example, if the rod from the tire to the horizontal strips is 5 mm 2, then they should already be 10 mm 2, and the rods should be 20 mm 2.
Errors in the device - what not to do
There should be several vertical rods; one driven into the ground is not enough. The resistance of the earth is strongly dependent on the area of the ground electrode that is in contact with it. For one grounding switch it is not sufficient to provide reliable protection. If two or more rods are separated by 1–2 m, a potential arises between them, and the effective contact area increases hundreds of times. You can’t spread them too far either: the potential surface will break, leaving just separate grounding conductors.
If the switchboard is located in a house and it is not possible to connect a steel busbar to it, a connection with a copper conductor is used. There is a misconception that it is enough to secure the pressed tip with a bolt and cover it with a protective conductive lubricant. It can protect against corrosion only in a dry room. The tire should be protected from moisture by placing it on the wall and closing it in a metal box.
Humidification promotes the formation of galvanic couples and electrocorrosion, which extends under the insulation. IN emergency situation the contact immediately burns out, especially since it is impossible to attach the grounding conductor directly to the ground electrode and cover it with soil.
It is also unacceptable to ground devices in series and connect several grounding conductors to one contact of the grounding bus. This threatens that the failure of one installation will cause a chain reaction, dragging down others.
Metal products with a hardened surface such as reinforcement, rails, and channels should not be used as a material. The increased density of their surface prevents the creation of good contact with the ground. You also shouldn't paint metal in hopes of resisting corrosion. It may not exist, but all meaning in such grounding is lost. The paint prevents reliable contact of the metal with the ground.
The biggest enemy of grounding is corrosion, which can sometimes reduce its effectiveness to zero after a few years. Therefore, before digging in, steel products should be coated with a special protective conductive coating.
Installation of grounding parts - circuit definition and assembly
Before starting work, we decide on the scheme. There are quite a lot of them, but the most common are two: closed and linear. Each option requires approximately the same consumption of materials, it's all about reliability.
A closed circuit is most often executed as a triangle, although it can have a different form. It is reliable in its functioning. If one jumper between the pins is damaged, it continues to work. For a private house, it is recommended to use a closed circuit - a triangle.
With the linear method, all the rods are arranged along a line, connecting in series. The disadvantage is that damage to one jumper reduces efficiency, and if it is the first, then performance is completely lost.
To create a grounding loop, you need to drive three pins vertically into the ground and connect them with grounding conductors located horizontally. In addition, a metal rod or tape should be connected from the grounding switch to connect to the electrical panel. Vertical grounding conductors are made from steel corners 50×50×5 mm, horizontal ones are made from steel strips 40×4 mm. We connect the circuit and the input shield with a rod of at least 8 mm 2. You can use other materials, which are described above, but we will show production using the example of these materials.
Having retreated about one meter from the foundation, we mark a triangle with sides of 1.2 m. Along the marking lines, we dig a trench to a depth of 1 m. We make the width sufficient to carry out welding work. This is a trench for horizontal ground lines.
We cut the ends of the squares with a grinder under acute angle to make it easier to score. We install them at the vertices of the triangle and hit them with a sledgehammer. They go quite easily, and after a few minutes the first one is ready, we do the same with the other two. If you have a drill, you can drill the well to reduce clogging. The rods should protrude 30 centimeters above the lower level of the trench.
When they are all in the ground, we proceed to connect them with horizontal stripes to create a closed loop. Using conventional welding, we weld the strips to the corners. We use welding, because the bolted connection in the ground will quickly collapse. Loss of contact will result in the grounding losing its functionality.
If there is no way to use welding, you can use bolts, but only above the ground surface. They are treated with conductive lubricant, periodically tightened and lubricated again.
We connect the assembled circuit to the shield. We weld a steel wire to the corner and lay it along the bottom of the trench to the electrical panel. At the other end we weld a washer to create reliable contact at the junction with the power supply. If there is no rod of a suitable cross-section, we use the same strip as for horizontal jumpers. It is even preferable; it has a larger contact area with the ground, but it is more difficult to work with. As a last resort, if it is not possible to bend the strip at the desired angle, we cut it into pieces and weld it from separate elements.
We treat the finished grounding loop with an anti-corrosion compound, after which it can be covered with earth. A structure made in this way will last for decades.
Connecting consumers - changes in wiring diagram
The matter is not limited to just installing an external grounding device. If there are three wires in the house, then no problems arise. But you will have to tinker with the old two-wire circuit. After all, it is not intended for grounding connection.
There are several options from which you can choose the most suitable:
- 1. We install new European sockets and run separate grounding wires from them to the panel. Through the electrical panel we connect them to the grounding bus.
- 2. Completely disconnect the old wiring. We disconnect it from the electrical panel and leave it in the wall, and lay the new one on top of it in plastic casings. We use old sockets for sockets and switches.
- 3. Change the two-wire circuit to a three-wire one. You don’t have to remove the old one, but leave it for lighting and connecting low-power devices. We install the three-wire cable separately after installing the new panel.
But at the input we have two wires left, connected via the TN-C system. At the transformer substation, the neutral is grounded, phase L is suitable through the air, and another core, which combines neutral protection with the working wire, is marked on the PEN diagrams. Your own ground loop should now be connected to home network. There are two ways to do this:
- convert the system from TN-C to TN-C-S;
- connect via TT system.
In a two-wire TN-C system there is no separate protective conductor. To convert it to TN-C-S, we divide the combined PEN wire into two separate ones: protective PE and working N. To determine it, we will use an indicator: on the phase one it will glow, but on the PEN we need there is no glow.
We install a busbar in the electrical input panel, metallic connected to its body. It will serve as a PE grounding bus; we connect the PEN wire to it, which comes from the street. We install two more busbars in the shield, isolated from the housing. We make a jumper to one of them, this will be the bus of the neutral working wire N. We connect phase L to the second isolated bus.
The use of the TT system does not require PEN separation wires. With this scheme, there is no electrical connection between the ground loop and the PEN conductor. Two wires enter the house through busbars isolated from the power supply housing. The electrical panel itself is grounded.
TT has advantages over the TN-C-S system, which requires separation of the PEN wire. If the zero is burned off from the input side of the TN-C-S system, all devices will be grounded to the circuit, which under some circumstances may cause negative consequences. With the TT system, the PEN wire does not have any connection with the home grounding, and there is guaranteed to be no voltage on the device housings.
The use of a CT circuit requires the mandatory presence of RCD devices protective shutdown. They will also be useful in the TN-C-S system. They will be especially useful in situations where there is an uneven phase load and a small voltage appears on the neutral conductor. When the network is electrically connected to the protective conductor, it may also appear on the device body. That's when the protection should work.
From the above we conclude that for a house with old wiring the best option is to use a TT circuit, and it is better to mount separate connections inside for grounding powerful devices.
When building or purchasing a private house, an electrical supply system will be connected to it, and therefore grounding measures will be needed. We suggest considering how to make a separate external and inner circuit grounding, the cost of its installation and PUE standards, as well as the price and where to buy materials.
What is it - a ground loop
A grounding device is a group of horizontal conductors - electrodes; they are installed in close proximity to the object at a certain distance relative to each other.
What is the circuit for?
- protection of electrical devices from voltage surges in premises;
- protection of home residents from electric shock;
- resistance to energy “spreading”;
- for lightning protection of a cottage, house or apartment.
Inner loop technology
To build such a group, it is customary to use steel angles or reinforcing bars. metal pipes, supports, up to 3 meters long. They are driven into the ground with a sledgehammer and, if necessary, secured with a foundation, but it is advisable not to fill them, otherwise, if repairs are needed, it will be impossible to carry out.
You need to connect them together using a thin steel strip with a thickness of 4 millimeters, which before starting work is laid in a trench up to a meter deep. We fasten everything together by welding.
To save space on the site, these groups are placed around the perimeter of the building, or common area. The contour is just like that geometric figure is formed when assessing work from above. Absolutely everything is connected to this grounding conductor electrical appliances houses, especially those that consume a load above average: from 380 V.
What does the circuit depend on?
Before starting work, it is necessary to take measurements and measure the resistance of the ground loop. This indicator depends on several factors, in particular:
- Condition of the ground flooring;
- Grounding installation depth;
- Soil quality and type (clay, black soil, sand, etc.);
- Number of grounding groups and electrodes in each group;
- Electrode material and its characteristics.
Ideally, you need to place the ground loop in black soil, clay soils and loams. It is strictly forbidden to install electrical resistance in stone covers or rocks, they also conduct current, and the resistance of these materials is very low.
Instructions for circuit design
Installation of a closed circuit is carried out as follows: a trench of the selected depth is dug, the optimal value is 70 centimeters, but if your apartment is filled with various types of power plants, then you can create a ditch up to a meter down. The shape of the trench is an isosceles triangle with a maximum width of one meter and a depth of about 07-1 m; it must first be measured.
A corner is hammered into the vertices of the triangle with a sledgehammer, which will be responsible for the initial resistance of the ground loop of a private house. The optimal pipe length for a regular building is 2-3 meters. If the reinforcement does not fit into the ground well, use a special drill, not a hammer. After this, we begin to install our grounding conductors along the trench.
Tips from an electrician:
After all the electrodes are closed, you need to lay a steel strip up to 4 mm thick, starting from the substation and moving around the perimeter.
You will need a drawing diagram of the site, because... installation of a ground loop in a private house or building is prohibited by SNIP over gas or water pipes. It can be drawn up schematically or using software (for example, the AutoCad program), this document will be needed when the inspection protocol is drawn up in accordance with GOST. In addition, you also need to take into account the permission from the energy supply company.
Video: how to make a ground loop in a house
Grounding loops can be constructed only if there is an act for hidden work.
Testing and evaluation
Afterwards, the ground loop must be connected and tested for resistance. To do this, we connect a multimeter to it in ommert mode, after which we connect all the devices in the room to grounding and measure the frequency of the pulses. The optimal rate is 60 pulses per minute.
What are the requirements for the grounding circuit:
- It is allowed to choose more wires than indicated in our comparison table, but not less;
- The strip connecting the electrodes must be made of corrosion-resistant alloy steel;
- The connections must be painted (the color is selected according to GOST);
The estimate is drawn up not only for the materials themselves, the prices for a typical grounding loop also take into account the work being done, because in any case you will have to invite an employee of the electricity supply company to evaluate the work, he will fill out a passport and issue a protocol.
- Fittings – 1500 rubles;
- Steel tape and its installation – 3000 rubles;
- Painting of connections – 300 rubles;
- Primary documentation – 200 rubles;
- Welding work when connecting to a boiler room - 200 kW (100 rubles);
- Wires used to lay grounding to the house wiring - 500 rubles;
The time frame for creating a circuit like a KTP or TP grounding is 3-5 days. The installation must be approached very responsibly, wear a protective suit and dielectric gloves, and use a mask when working with welding.
Grounding a private house or apartments. Many people wonder if they should ground a private home or can they do without it? The answer is unequivocal - grounding of a private house is necessary, moreover, according to the PUE for the construction of new and major repairs old houses, grounding of a private house is mandatory. Installation of grounding of a private house is important stage when installing the power supply system for your private home, cottage or apartment. Properly designed grounding of a private home means the electrical safety of your home, electrical appliances, and most importantly, health and life.
To begin with, let us turn to the electrical literature, in particular to the Rules for the Construction of Electrical Installations, according to clause 1.7.28:
Grounding - uh something deliberate electrical connection any point in the network, electrical installation or equipment with a grounding device.
I won’t go into the abstruse wording of textbooks or specials. literature, I will try to explain why it is necessary to ground a private house in simple accessible language.
If in simple words, grounding a private house is a connection by wire between the equipment housing and the ground loop.The grounding of a private house is an ordinary mello structure, mounted to specified dimensions, from certain materials and “hidden” in the ground.
Grounding a private house (metal structure) using copper wires, cross-section not less than 10 sq.mm. or steel plate,
connects to, in which the grounding wire, through the terminal block, is connected to the grounding conductors of cables laid in a house or apartment to sockets, lamps and other electrical receivers.
Sockets, which must be three-pin (phase-neutral-ground), are connected with a plug to our household electrical appliances through a special third “grounding” contact.
That is, the following “route” of the PE grounding conductor is obtained: electrical appliance - plug - socket - terminal block in the electrical panel - grounding wire (bus) - ground loop - ground.
Grounding a private house is done, first of all, for the electrical safety of people. Surely, many people are familiar with this situation when touching an old refrigerator or washing machine produces a slight, but sometimes very noticeable electric shock. This happens in old housing stock, where there is no grounding of a private house, i.e. Only two wires are suitable for sockets: phase and neutral, without a third protective PE wires Electric shock occurs due to poor insulation of the refrigerator or washing machine (the insulation is damaged electric wire, engine, compressor, etc.), and voltage (potential) appears on their housing. And when you touch the body of a refrigerator or washing machine, for example with your hand, especially if it is wet, you are “grounding” the refrigerator or washing machine, and then a small current “runs” through you to the “ground”.
If your electrical network at home, cottage or apartment has a third PE protective wire, then if the insulation of a refrigerator or machine is broken, the current will “run away” through it to the ground loop. And when you touch the body of electrical equipment that is grounded, but with poor insulation, you will not feel anything, because the current always “runs” along the path of least resistance. In our case, human resistance ( approximately 1000 Ohm) will be much greater than the resistance itself protective wires + ground loop resistance, which will be approximately several dozens Ohm.
Grounding a private house is also necessary to protect our household electrical appliances. A person is often a “carrier” of static charge, which depends on many factors, ranging from clothing to the level of humidity in the room; the current is very small, but the voltage reaches several thousand volts, which can damage delicate electronics in electrical appliances.
But grounding a private house will not allow this to happen and will “discharge” static electricity into the ground. Also, grounding a private house does not allow a static charge to accumulate to significant levels on the housings of electrical appliances themselves; in this case, the charge constantly “drains” into the ground.
This is a simple and, I hope, understandable explanation of why grounding of a private house, cottage or apartment is necessary. An electric charge, whether it is damage to the insulation of an electrical appliance, or accumulated statically, when grounded, constantly “goes” into the ground, because the housing of electrical equipment and the grounding loop of a private house, figuratively speaking, are one whole.
How to properly install the grounding of a private house yourself can be read in a separate article ““.
Thank you for your attention.
General requirements
Grounding is one of the main protection measures against damage electric shock.
This article provides detailed, step by step instructions about how to make grounding in a private house with your own hands.
To begin with, let's define what is grounding?
According to the PUE Grounding- this is an intentional electrical connection of any point in the network, electrical installation or equipment with a grounding device. (clause 1.7.28.)
As a grounding device use metal rods or angles that are driven vertically into the ground (so-called vertical grounding conductors) and metal rods or metal strips that, by welding, connect vertical grounding rods (so-called horizontal grounding conductors).
Vertical and horizontal grounding conductors together form grounding kennel, this contour can be closed (Figure 1) or linear (Figure 2):
The grounding loop must be connected to the main grounding bus in the incoming electrical panel of the house using grounding conductor which, as a rule, uses the same metal strip or rod that is used as a horizontal grounding conductor.
The protective grounding of a private house will have the following general form:
In turn, the combination of the grounding loop and the grounding conductor is called grounding device.
A closed grounding loop is usually made in the shape of a triangle with sides of 2 to 3 meters (depending on the length of the vertical grounding conductors); it is important that the distance between the vertical grounding conductors is not less than their length (see Fig. 1). A closed contour can also be made in other shapes, for example oval, square, etc. In turn, a linear circuit consists of a series of vertical grounding electrodes, 3-4 in number, lined up in a line, and, as in the case of a closed circuit, the distance between them in a linear circuit must be no less than their length, i.e. from 2 to 3 meters (see Fig. 2).
Note: A closed ground loop is considered more reliable, because even if one of the horizontal grounding conductors is damaged, this circuit remains operational.
Horizontal and vertical grounding conductors must be made of black or galvanized steel or from copper (clause 1.7.111. PUE). Due to their high cost, copper grounding conductors, as a rule, are not used. Also Grounding conductors should not be made from reinforcement - The outer layer of the reinforcement is hardened, which disrupts the distribution of current across its cross section; in addition, it is more susceptible to corrosion.
Vertical grounding conductors are made from:
- round steel rods with a minimum diameter of 16mm (recommended: 20-22mm)
- steel corners with dimensions of at least 4x40x40 (recommended: 5x50x50)
Length of vertical ground electrodes should be 2-3 meters(at least 2.5 m recommended)
Horizontal grounding conductors are made from:
- round steel rods with a minimum diameter of 10mm (recommended: 16-20mm)
- steel strip measuring 4x40
The grounding conductor is made of:
- round steel rod with a minimum diameter of 10mm
- steel strip measuring at least 4x25 (recommended 4x40)
2. Grounding installation procedure:
STEP 1— Choosing a place for installation
The installation location is selected as close as possible to the main electrical panel (input panel) of the house in which the main grounding bus (GZSh), also known as PE bus, is located.
If the incoming electrical panel is located inside the house or on it external wall The grounding loop is mounted near the wall on which the electrical panel is located, at a distance of approximately 1-2 meters from the foundation of the house. If the electrical panel is located on an overhead power line support or on a remote rack, the ground loop can be mounted directly under it.
In this case, you should not place (use) grounding electrodes in places where the ground is dried under the influence of heat from pipelines, etc. (clause 1.7.112 PUE)
STEP 2— Earthworks
We dig a trench in the shape of a triangle - for installing a closed grounding loop, or a straight line - for a linear one:
Trench depth should be 0.8 - 1 meters
Trench width should be 0.5 - 0.7 meters(for convenience welding work in the future)
Trench length- depending on the selected number of vertical ground electrodes and the distances between them. (For a triangle, 3 vertical earth electrodes are used, for a linear circuit, as a rule, 3 or 4 vertical earth electrodes)
STEP 3— Installation of vertical grounding conductors
We place vertical grounding rods in the trenches on required distance from each other (1.5-2 meters), after which we hammer them into the ground using a hammer drill with a special attachment or a regular sledgehammer:
The ends of the grounding conductors must first be sharpened for easier entry into the ground:
As already written above, the length of the vertical ground electrodes should be approximately 2-3 meters (a minimum of 2.5 meters is recommended), and it is necessary to drive them into the ground for the entire length, so that the upper part of the ground electrode protrudes above the bottom of the trench by 20-25 cm : 
When all vertical grounding rods are driven into the ground, you can proceed to the next step.
STEP 4— Installation of horizontal grounding conductors and grounding conductor:
On at this stage it is necessary to connect all vertical grounding conductors to each other using horizontal grounding conductors and weld a grounding conductor to the resulting grounding loop, which will come out of the ground to the surface and is intended to connect the grounding loop to the main grounding bus of the input electrical panel.
Horizontal and vertical grounding conductors are connected to each other by welding, and the junction must be welded on all sides for better contact.
IMPORTANT! Not allowed to use bolted connections! Vertical and horizontal grounding conductors forming the grounding loop, as well as the grounding conductor at the point of its connection to the grounding loop, must be connected by welding.
Welded seams must be protected from corrosion, for which the welding areas can be treated with bitumen mastic.
IMPORTANT! Myself The grounding circuit must not be painted!(clause 1.7.111. PUE)
The result should look something like this:
STEP 5— We fill the trench with soil.
Everything is simple here, we fill the trench with the mounted grounding loop with earth, so that there is at least 50 cm of soil above the loop, as already mentioned above.
However, there are some subtleties here too:
IMPORTANT! Trenches for horizontal grounding conductors must be filled with homogeneous soil that does not contain crushed stone and construction waste (clause 1.7.112. PUE).
STEP 6— Connecting the grounding conductor to the main electrical panel (input device).
Finally, we have come to the final stage - grounding the electrical panel of the house, for this we perform the following work:
We bring the grounding conductor to the electrical panel, so that there is about 1 meter left to the electrical panel; if the input panel is located in the house, it is advisable to bring the grounding conductor into the building. In this case, the following identification mark must be provided at the points where grounding conductors are inserted into buildings (clause 1.7.118. PUE):
The grounding conductor itself, located above the surface of the earth, must be painted; it must have a color designation with alternating longitudinal or transverse stripes of the same width (from 15 to 100 mm) of yellow and green colors. (Clause 1.1.29. PUE).
We weld a bolt to the end of the grounding conductor from the side of the electrical panel, to which we connect a flexible copper wire with a cross section of at least 10 mm 2, which should also have a yellow-green color. We connect the second end of this wire to the main grounding bus, which should be used as a bus inside the input device (input electrical panel of the house). RE(Clause 1.7.119. PUE).
IMPORTANT! The main grounding bus should, as a rule, be copper. It is allowed to use a main grounding bus made of steel. The use of aluminum tires is not permitted. (Clause 1.7.119. PUE).
As a result, the grounding diagram of the house shield should look like this:
I am not a professional builder or electrician, so when building my frame house I always start by studying theory and guidance documents(SNiP, PUE, etc.). When connecting 380 V, when the issue of grounding arose, I again turned to theory.
General provisions of the grounding system in a private house (3 phase, 380 V)
According to the PUE (ed. 7), electrical installations with voltage up to 1 kV in relation to electrical safety measures are divided into:
- electrical installations in networks with a solidly grounded neutral;
- electrical installations in networks with isolated neutral.
Open conductive Part - conductive part of the electrical installation accessible to touch, normally not under voltage, but which may become live if the main insulation is damaged.
For electrical installations with voltage up to 1 kV, the following designations are accepted:
- - system TN, in which the functions of zero protective PE and zero working N conductors are combined in one conductor in some part of it, starting from the power source (it can be obtained by making some changes to TN-C);
- TT - a system in which the neutral of the power source is solidly grounded, and the exposed conductive parts of the electrical installation are grounded using a grounding device that is electrically independent from the solidly grounded neutral of the source (i.e. zero N and grounding PE are isolated from each other).
Designation of other systems
- TN- a system in which the neutral of the power source is solidly grounded, and the open conductive parts of the electrical installation are connected to the solidly grounded neutral of the source through neutral protective conductors;
- TN-C - system TN, in which the neutral protective and neutral working conductors are combined in one conductor along its entire length (most common in Russia);
- TN-S- system TN, in which the zero protective and zero working conductors are separated along its entire length;
- IT - a system in which the neutral of the power supply is isolated from earth or grounded through instruments or devices having high resistance, and exposed conductive parts of the electrical installation are grounded.
Drawings of TN-C, TN-S, TN-C-S systems
Decoding letter designations
Decoding of letter designations:
- Subsequent (after N) letters - combination in one conductor or separation of the functions of the zero working and zero protective conductors:
- S- zero worker (N) and zero protective (RE) conductors are separated;
- WITH - the functions of the zero protective and zero working conductors are combined in one conductor ( PEN-conductor);
- The second letter is the state of exposed conductive parts relative to ground:
- T - exposed conductive parts are grounded, regardless of the relation to the ground of the neutral of the power source or any point of the supply network;
- N- exposed conductive parts are connected to the solidly grounded neutral of the power source.
- The first letter is the state of the neutral of the power source relative to ground:
- T - grounded neutral;
- I - isolated neutral.
- N- zero working (neutral) conductor;
- RE -protective conductor(grounding conductor, neutral protective conductor, protective conductor of the potential equalization system);
- PEN- combined zero protective and zero working conductors.
Choosing a grounding system for a private home
For the modern private sector, only two grounding systems TT and TN-C-S are suitable. Almost all private sector powered by transformer substations with a solidly grounded neutral and a four-wire power line (three phases and PEN, combined working and protective zero or, in other words, combined zero and ground).
Features of the TN-C-S grounding system
According to clause 1.7.61 of the PUE, when using the TN system, it is recommended to re-ground the PE and PEN conductors at the entrance to the electrical installations of buildings, as well as in other accessible places. Those. conductor PEN at the entrance to the house it is re-grounded and is divided into PE and N. After this, 5 or 3 wire wiring is used.
Switching PEN and PE is strictly prohibited (PUE 7.1.21. In all cases, it is prohibited to have switching contact and non-contact elements in circuits of PE and PEN conductors). The separation point must be located before the switching device. It is forbidden to break PE and PEN conductors.
Disadvantage of the TN-C-S system
- If the PEN conductor breaks, dangerous voltage may appear on the housings of grounded electrical appliances.
Description of the TN-C-S system - Description of the TN-C-S system
It is recommended to use the TN-C-S grounding system only on modern power lines made with SIP wire in which a break in only one wire is unlikely. Clause 1.7.61 of the PUE establishes that when using the TN system it is recommended to re-ground PE and PEN conductors at the entrance to electrical installations of buildings, as well as in other accessible places. Besides, Re-grounding on power lines must be carried out. For re-grounding, natural grounding should be used first. The resistance of the re-grounding electrode is not standardized. Clause 1.7.103 PUE establishes that the total resistance to spreading of grounding conductors (including natural ones) of all repeated grounding The PEN conductor of each power line at any time of the year should be no more than 5, 10 and 20 Ohms, respectively, at line voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 V of a single-phase current source. In this case, the spreading resistance of the grounding conductor of each of the repeated groundings should be no more than 15, 30 and 60 Ohms, respectively, at the same voltages. These conditions reduce to zero the possibility of hazardous potential appearing on the housings of electrical appliances.
According to clause 1.7.135 of the PUE, when the zero working and zero protective conductors are separated starting from any point in the electrical installation, it is not allowed to combine them beyond this point along the distribution of energy. At the point of separation PEN- conductor for the neutral protective and neutral working conductors, it is necessary to provide separate clamps or busbars for the conductors, interconnected. PEN-the supply line conductor must be connected to the terminal or zero protective bus RE- conductor.
To ensure high level safety from electric shock in the TN-C-S system, it is necessary to use residual current devices (RCDs).
Features of the CT grounding system
Description of the TT system - Description of the TT system
The TT system differs from TN-C-S only in the absence of a connection between the PEN conductor and the grounding of the house, i.e. the protective conductor PE is grounded independently of the neutral working conductor N and any connection between them is prohibited. Therefore, in schemes, PEN is usually denoted as N, since we do not receive PE from PEN.
Comment
According to clause 1.7.54 of the PUE, artificial and natural grounding conductors can be used for grounding electrical installations. If, when using natural grounding conductors, the resistance of the grounding devices or the touch voltage has an acceptable value, and the normalized voltage values on the grounding device and the permissible current densities in natural grounding conductors are ensured, the implementation of artificial grounding conductors in electrical installations up to 1 kV is not necessary.
The use of natural grounding conductors as elements of grounding devices should not lead to their damage when currents flow through them short circuit or to disrupt the operation of devices with which they are associated.
The following can be used as natural grounding conductors (clause 1.7.109 of the PUE):
- metal and reinforced concrete structures buildings and structures in contact with the ground, including reinforced concrete foundations of buildings and structures with protective waterproofing coatings in non-aggressive, slightly aggressive and moderately aggressive environments;
- metal water pipes laid in the ground;
- casing pipes for drilling wells;
- metal sheet piles of hydraulic structures, water conduits, embedded parts of gates, etc.;
- mainline non-electrified rail tracks railways and access roads in the presence of a deliberate arrangement of jumpers between the rails;
- other metal structures and structures located in the ground;
- metal shells of armored cables laid in the ground. Cable sheaths can serve as the only grounding conductors when there are at least two cables. Aluminum shells cables are not allowed to be used as grounding conductors.
The following are not allowed to be used as grounding conductors:
- pipelines of flammable liquids, flammable or explosive gases and mixtures;
- sewerage and central heating pipelines.
The specified restrictions do not exclude the need to connect such pipelines to a grounding device for the purpose of equalizing potentials in accordance with 1.7.82.
Artificial ground electrodes can be made of black or galvanized steel or copper, and must not be colored.
The method of installation of vertical grounding conductors depends on the following factors:
- dimensions of grounding electrodes;
- the nature of the soil, its moisture and condition during installation;
- time of year and climatic conditions(thawed, frozen);
- number of immersed electrodes;
- the distance of objects from each other, as well as the availability and possibility of using mechanisms and devices necessary for installation.
The smallest dimensions of grounding conductors and grounding conductors laid in the ground
|
Material |
Section profile |
Diameter, mm |
Cross-sectional area, mm |
Wall thickness, mm |
| Black steel | Round: | |||
| 16 | - | - | ||
| 10 | - | - | ||
| Rectangular | - | 100 | 4 | |
| Angular | - | 100 | 4 | |
| Pipe | 32 | - | 3,5 | |
| Galvanized steel | Round: | |||
| for vertical grounding conductors | 12 | - | - | |
| for horizontal grounding conductors | 10 | - | - | |
| Rectangular | - | 75 | 3 | |
| Pipe | 25 | - | 2 | |
| Copper | Round | 12 | - | - |
|
Rectangular |
- | 50 | 2 | |
| 20 | - | 2 | ||
|
Multi-wire rope |
1,8* | 35 | - | |
* Diameter of each wire.
Laying bare aluminum conductors in the ground is not permitted.
Rational methods for installing grounding electrodes in a private house:
- for thawed, soft soils - pressing and screwing in rod electrodes, driving and pressing in profile electrodes;
- for dense soils – driving in electrodes of any cross-section;
- for frozen soils – vibration immersion;
- for rocky and frozen soils, if deep immersion is necessary - backfilling into a drilled well.
The denser the soil is adjacent to the conductor, the lower the resistance (i.e., the minimum resistance to spreading is for a clogged electrode, and the maximum is for an electrode placed in a finished well and covered with loose soil).
More details
The resistance of the electrodes increases slightly when pressed into the ground and when immersed with vibrators and exceeds the resistance of clogged electrodes by only 5-10%.
After 10-20 days, the resistance of the electrodes, immersed in vibrators, pressed in and clogged, begins to level out. Much more time is required to restore the soil structure and reduce the resistance of electrodes screwed into the soil, especially when using an expanded tip on the electrode, which makes immersion easier, but loosens the soil.
It is advisable to locate the place for electrical installation of the grounding loop near the grounded electrical installation (power panel). You will need a corrosion-resistant steel angle (50 x 50 x 5 mm) or a rod and a corrosion-resistant steel strip (4 x 40 mm) to connect the grounding electrodes themselves and the grounding loop and power panel. Most often, an equilateral triangle (3 x 3 x 3 meters) is dug, along the tops of which 3 grounding electrodes are driven (in order for the corner to be driven freely into the ground, its ends must be sharpened using a grinder). A corrosion-resistant steel strip is welded around the perimeter to three ground electrodes (corners) installed in the ground. Next, a trench is dug (0.5 meters wide and 0.8 meters deep) to the house. We lay a steel strip in the trench. We weld one end of the strip to the ground loop, and connect the other to the PE bus in the ASU. We dig trenches with homogeneous soil that does not contain crushed stone and construction waste. All ground loop connections are made by welding.
The length of vertical electrodes is determined by the design, but should not be less than 1 m; the upper end of vertical grounding conductors should be buried, as a rule, by 0.5-0.7 m.
Horizontal grounding conductors are used to connect vertical grounding conductors or as independent grounding conductors. The laying depth of horizontal grounding conductors is at least 0.5-0.7 m. A smaller laying depth is allowed in places where they are connected to equipment, when entering buildings, when crossing underground structures and in areas of permafrost and rocky soils.
Horizontal grounding conductors made of strip steel should be laid on the edge of the trench at the bottom.
Trenches for horizontal grounding conductors must be filled first with homogeneous soil, not containing crushed stone and construction waste, compacted to a depth of 200 mm, and then with local soil.
When driving vertical ground electrodes, you can use steel electrodes of any profile - angle, square, round, however, the lowest metal consumption (with the same conductivity) and the greatest resistance to soil corrosion (in the case of equal metal consumption) are achieved when using rod electrodes made of round steel.
When driving into ordinary soils to a depth of up to 6 m, it is economical to use rod electrodes with a diameter of 12-14 mm. At depths of up to 10 m, as well as when driving short electrodes into particularly dense soils, more durable electrodes with a diameter of 16 to 20 mm are required.
Horizontal grounding conductors can be made of round, strip or any other steel. Preference should be given to round steel, which, with the same mass and conductivity, has a smaller surface and greater thickness, as a result of which it has less corrosion vulnerability (it is recommended to use low-carbon round steel).
If there are reservoirs near objects, extended grounding conductors are laid at the bottom of the reservoirs, and connecting cables or cables are laid from them. air lines to objects.
Sections of grounding conductors in electrical installations with voltage up to 1 kV:
| Cross-section of phase conductors, mm 2 | Minimum cross-section of protective conductors, mm |
| S < 16 | S |
| 16 < S < 35 | 16 |
| S > 35 | S/2 |
The grounding conductor connecting the working (functional) grounding conductor to the main grounding bus in electrical installations with voltage up to 1 kV must have a cross-section of at least:
- copper - 10 mm 2,
- aluminum - 16 mm 2,
- steel - 75 mm 2.
Main ground bus
According to clause 1.7.121 of the PUE, the following can be used as PE conductors in electrical installations with voltage up to 1 kV:
- specially provided conductors:
- cores of multi-core cables;
- insulated or non-insulated wires in a common sheath with phase wires;
- permanently laid insulated or non-insulated conductors;
- exposed conductive parts of electrical installations:
- aluminum cable sheaths;
- steel pipes for electrical wiring;
- metal shells and supporting structures of busbars and complete devices of factory production (provided that the design of the boxes and trays provides for such use, as indicated in the manufacturer’s documentation, and their location excludes the possibility of mechanical damage);
- Some third party conductive parts:
- metal building structures of buildings and structures (trusses, columns, etc.);
- reinforced concrete reinforcement building structures buildings, subject to the requirements of 1.7.122;
- metal structures for industrial purposes (crane rails, galleries, platforms, elevator shafts, elevators, elevators, channel frames, etc.).
P. 1.7.122. The use of exposed and third-party conductive parts as PE conductors is permitted if they meet the requirements of this chapter to conductivity and continuity electrical circuit .
Neutral protective conductors of circuits are not allowed to be used as neutral protective conductors of electrical equipment powered by other circuits, and also to use open conductive parts of electrical equipment as neutral protective conductors for other electrical equipment, with the exception of shells and supporting structures busbars and complete prefabricated devices that provide the ability to connect protective conductors to them in the right place.
The use of specially designed protective conductors for other purposes is not permitted.
The main grounding bus can be made inside the input device of an electrical installation with voltage up to 1 kV or separately from it (clause 1.7.119. PUE).
Inside the input device, a PE bus should be used as the main grounding bus.
When installed separately, the main grounding bus must be located in an accessible, convenient place for maintenance near the input device.
The cross-section of a separately installed main grounding bus must be no less than the cross-section of the PE (PEN) conductor of the supply line.
The main grounding bus should, as a rule, be copper. It is allowed to use a main grounding bus made of steel. The use of aluminum tires is not permitted.
The design of the bus must provide for the possibility of individual disconnection of the conductors connected to it. Disconnection must only be possible using a tool.
Third-party conductive parts may be used to connect multiple main ground bars if they meet the electrical continuity and conductivity requirements of 1.7.122.
Connections and connections of grounding, protective conductors and conductors of the equalization and potential equalization system
Connections and connections of grounding, protective conductors and conductors of the equalization and potential equalization system must be reliable and ensure continuity electrical circuit (i.e. it is not allowed to break the specified circuits with fuses, circuit breakers, etc., clause 1.7.139).
It is recommended to make connections of steel conductors by welding. It is allowed to connect grounding and neutral protective conductors in indoor and outdoor installations without aggressive environments in other ways that meet the requirements of GOST 10434 “Electrical contact connections. General technical requirements» to class 2 connections.
Connections must be protected from corrosion and mechanical damage. For bolted connections, provisions must be made to prevent contact loosening.
Connections of protective conductors of electrical wiring and overhead lines should be made using the same methods as connections of phase conductors.
When using natural grounding conductors for grounding electrical installations and third-party conductive parts as protective conductors and potential equalization conductors, contact connections should be made using the methods provided for by GOST 12.1.030 “SSBT. Electrical safety. Protective grounding, grounding.”
The connection of each open conductive part of the electrical installation to the neutral protective or protective grounding conductor must be made using a separate branch. The series connection of exposed conductive parts into the protective conductor is not permitted.. (clause 1.7.144. PUE).
According to clause 1.7.145, it is not allowed to connect switching devices in circuits of PE and PEN conductors, with the exception of cases of powering electrical receivers using plug connectors.
If the body of the socket outlet is made of metal, it must be connected to the protective contact of that socket.
