How to collect grounding. Grounding in a private house, ground loop diagram

Life is saturated with electrical appliances. The "Khrushchev" energy consumption rate of 1.3 kW per apartment (220 V; traffic jams - 6 A) now causes laughter. Electrical appliances provide comfort and save a lot of money, but there is a downside to the coin: the danger of electric shock increases. Therefore, without protective grounding (and for washing machine- and a worker) is now indispensable. But in old houses it is not, and the private trader needs to do it himself; prices in specialized organizations correspond to the volume of work. It is easier than paying that kind of money to do grounding in the house with your own hands - the work is not easy, but not difficult either.

Is it possible to do grounding yourself?

But will there be any problems with the electricians? They love to punch.

If the grounding is done correctly, and the measurements showed a current spreading resistance of no more than 4 ohms, there will be no formal reason for nit-picking. The grounding device of the house is regulated in detail by the following regulatory documents:

PTBE - Safety regulations for the operation of consumer electrical installations.
PUE - Rules for the installation of electrical installations of consumers.
PTEE - Rules technical operation consumer electrical installations.

However, neither in a dream, nor in spirit, nor in plain text does it say that grounding should be done by a specialized organization. Made according to the rules, complies with the norms - protect your health, there can be no complaints. This article describes how to properly ground a private house and arrange grounding in an apartment if the house is not grounded.

But! If the grounding is done by a specialized organization for the project, checked and accepted by the energy service, and still an accident occurs, you have every right to claim damages. With self-made grounding, this possibility, of course, is excluded. You can order a project from the power engineers, pay for the acceptance of the finished one, get your hands on a commissioning certificate. However, practice shows that if it "shied away", it is useless to sue the power engineers. And in the contract with a commercial firm, compensation for damage is prescribed. But the work is also very expensive.

Protective and working grounding

Protective grounding saves people from electric shock, and the equipment included in the network from failure if an electrical appliance breaks down on the case. In the presence of a lightning rod - also in case of a lightning strike.

Working grounding in an electrical state of emergency plays the role of a protective one, but it also provides normal work electrical equipment. permanent working ground used only in industrial equipment. For household appliances, grounding through a euro socket is considered sufficient. But in real conditions, it is still useful to ground some of the “everyday life” tightly:

Washing machine. She has a big electrical capacitance, and in a humid room, a fully functional machine, even included in a securely grounded euro socket, can harmlessly, but noticeably, “pinch”.
Microwave. It is known that a microwave source operates in it - a high-power magnetron. With poor contact in the outlet, the microwave can “siphon” at a level dangerous to health. On many microwaves, you can see a screw terminal on the back for a separate ground electrode, and the instructions bashfully keep silent about this: the presence of such a terminal transfers the device from the category of household appliances to industrial equipment. And so - well, this is such a decorative element.
Electric oven and induction cooker (hob). The internal wiring in them works in difficult conditions, the power is large, so the probability of breakdown is also high.
Desktop computer. His impulse block For the sake of compactness, the power supply (UPS) is designed in such a way that more washing machine gives a normal working leak. From such floating potentials on the case, performance decreases, and “glitches” are added, and the Internet speed drops. You can firmly ground the computer for any mounting screw on the back.

Grounding Parts

Earthing switches- driven or dug into the ground metal conductors. At least half a meter of the ground electrode must be below the maximum freezing horizon; in places with a positive winter - below the drying horizon, i.e. in a layer of soil with stable moisture. Most often, this is ensured with a ground electrode length of 2-3 m. Accurate data on the required length and number of ground electrodes can be obtained from the local energy service.

Metal communication- a welded metal structure connecting the upper ends of the ground electrodes and brought into the house in the form of a ground bus. There can be several inputs of grounding buses in the house, but one must certainly ground the input shield (VSC, or input-distribution device - ASU). Grounding conductors with metal bonding form a rigid integral ground loop.

Grounding conductors connect the ground terminals of electrical installations to the ground bus. They can be either bare rigid or flexible stranded in insulation. In the latter case, their cross section must be at least 4 sq. mm, and the color of the shell is yellow with a longitudinal green stripe. Let us transfer the ground conductor from the bus to the ground bus.

Grounding conductors are connected to the ground bus to special contact pads: its sections cleaned to a shine and lubricated with grease with threaded holes of at least M4 for bolts. Lubrication, in addition to protection against oxidation, is needed to prevent electrocorrosion (see next section).

A number of pads are indicated on one or both sides, if it is on the transit section of the bus, in pairs of oblique, at an angle of 45 degrees, black stripes. Solid coloring of the ground bus is unacceptable, but it is permissible to embed it, except for the contact rows, into the wall.

The electrical resistance of the metal connection is measured from the GROUND TERMINAL of the electrical installation to the ground part of the ground loop that is the most remote from it. That is, the ground conductor is electrically considered part of the metal bond. The resistance of any metal bond must not exceed 0.1 ohm.

Why multiple grounding conductors?

One ground electrode cannot be dispensed with, because the earth is a non-linear conductor. Its resistance strongly depends on the applied voltage and the area of contact with the ground electrode. One earth electrode has too little surface area to provide reliable protection. A potential surface appears between two grounding conductors separated by 1-2 m, and the effective area of contact with the ground increases hundreds of times. But it is impossible to spread the ground electrodes too far: the potential surface will break, and only two ground electrodes will remain. The optimal distance between ground electrodes in loose soil outside the permafrost zone is 1.2 m.

How not to ground

Clause 1.7.110 of the PUE categorically prohibits grounding electrical installations on any pipelines. "Ham radio" grounding on a water pipe is now also unacceptable: any piece plastic pipe in house wiring greatly increases the damaging effect of the breakdown current. And what will happen, both legally and in your own way, if your breakdown kills the neighbor’s wife taking a shower, there is no need to explain.

It is also forbidden to bring out the ground conductors and connect them to the ground bus on unprepared contact pads. In the figure on the right - twice unusable grounding.

The point here is that each metal has its own electrochemical potential. With inevitable moisture from the outside, a galvanic couple is formed and electrocorrosion begins; lubrication saves from it only in a dry room. The corrosion process extends under the shell of the grounding conductor. The owner is in full confidence that “his grounding protects him”, but in case of an accident, the grounding conductor instantly burns out.

It is also forbidden to ground electrical installations in series, through each other, and connect more than one grounding conductor to one contact pad of the ground bus (fig. below). In the first case, one emergency installation will “pull” others along with it, and all of them will interfere with each other; This is called electromagnetic incompatibility. In both cases, work to eliminate the accident is associated with a risk to life.

About lightning rods

According to the PUE, an object equipped with a ground loop must also be equipped with a lightning rod. A lightning rod is especially needed in the country. Summer cottages are already places preferred for lightning strikes: after all, summer residents, trying to supply themselves with water, dig, clog, lay water pipes shallowly or even on the surface of the soil. Country buildings are mostly built from combustible materials, and the fire brigade is far away, and a strong wind always accompanies a thunderstorm.

There are cases when entire summer cottages burned out from a lightning strike. And if a ground loop is found in a fire, but there are no remains of a lightning rod, both the authorities and neighbors do not need to look for the culprit for a long time.

The simplest lightning rod is two pointed fittings sticking up from the ends of the roof ridge by 1.2–1.5 m. They are connected to the contour with a steel wire of at least 6 mm, or a steel tire 15x3 mm, or a strip of several layers of galvanization, typed up to the desired section - 45 sq. mm.

The lightning guide bus should not be wider than 60 mm, otherwise, when a lightning strikes, plasma splashing will occur, the consequences of which are devastating. Simply put, a tire that is too wide will act as a kind of antenna, not diverting lightning to the ground, but spreading it to the sides.

All parts of the lightning rod are connected only by welding. The puff tire must be welded along the edges with tacks in increments of 50-60 cm with the capture of all layers.

Grounding a private house

The ground loop of a private house can be made different ways depending on the characteristics of the structure and properties of the soil. The three most common are shown in the figure. In all cases, it is better to make earth electrodes from pipes with an end flattened at the tip. At the bottom half a meter of the pipe, a dozen or one and a half holes of 5-8 mm are drilled randomly. In summer, in hot and dry weather, a salt solution can be poured into such a ground electrode (half a pack per bucket of water) so that the spreading resistance is kept normal.

Also, in all cases, the ground bus is the same as for the lightning rod. But it is impossible to use a “puff” of galvanized metal for metal bonding: it will quickly rust.

Different types of ground loops

For a country house or similar housing, as well as a working ground in the presence of protective grounding, a simple circuit is built (in the figure - on the right). In constantly wet soil or for working grounding, two ground electrodes can be dispensed with; for protective grounding, three are needed, located in a row or, better, a triangle. Ground electrodes are placed no closer than 1.2 m from the edge of the blind area.

A linear circuit with two groups of grounding conductors (middle figure) must be done if at least one of the following factors is present:

The electrical input is underground through the VSC.
Communications are brought into the house: water, sewerage, gas, communication, in any combination, or at least one of them.
Long-term (over 20 min.) power consumption exceeds 1 kW.

Finally, a full ground loop (left figure) is required if any of the following are present:

Electrical input - 220/380 V through the ASU or SCHVS (input power board).
The total area of the premises is over 100 sq. m.
Long-term power consumption - over 3 kW.
The presence of stationary electrical installations of an industrial type (with a ground terminal; for example, a drilling machine, a circular saw, etc.).
Availability of DGU backup power supply.

Ground measurement

You have made a contour for yourself, and, of course, you want to make sure that it will protect you reliably. To do this, it is necessary to measure the resistance of current spreading in the soil and the resistance of the metal bond. For this, professionals use special devices, both the old Soviet PKP-3 and modern electronic ones.

You cannot measure grounding with a household tester: the data will be reliable when a measuring voltage of 600 V is applied. Recall that the ground is a non-linear conductor. Therefore, borrow or rent an electronic ground meter or an old but reliable electric induction hand-held megger - megger. Meggers are still in use: they do not have any electronics, they do not require power supply, they are insensitive to interference in the measuring wires and do not create noise in the measured circuit. True, you cannot measure the metal connection with a megger, but for a welded circuit and properly connected grounding conductors, it has been normal for decades.

The spreading resistance of a megger connected to ohms is measured according to the diagram in the figure. The distance of a pair of measuring electrodes (they are on the right) to the corner or edge of the metal connection is 12-15 m. The electrodes must be bare and polished to a shine; metal - any. The electrodes are immersed in the ground by 0.6-1 m at a distance of 1.2-1.5 m from each other.

The polarity of the megger connection must be observed: the protective earth must withstand a lightning strike. Ordinary lightning is negative, i.e. are a stream of electrons. Isolated cases of positive lightning have been noted: a thick column of fire shoots from the ground straight into the sky. But the destructive power natural disaster approximately equal to the explosion of a tactical nuclear charge, only without penetrating radiation and radioactive contamination of the area, so grounding from positive lightning does not save.

Actually, the measurement procedure is elementary: they turn the megger handle and see how much the arrow showed on the scale.

Warning: using mains voltage, a quenching resistor and a milliammeter to measure grounding is deadly!

Video: an example of installing a grounding kit

Apartment grounding

In the USSR and the Russian Federation until 1997, power supply apartment buildings was carried out according to the scheme with a dead-earthed neutral (TN–C scheme). In this scheme, the house conductor of the protective earth (PE) is combined in the neutral of the three-phase input (N). This scheme gives great savings in metal, and in the vast USSR, with the need for intensive housing construction and strict centralized management of energy services, in times of low saturation of housing with electrical appliances, it was fully justified. But it has two significant drawbacks, "in all its glory" manifested itself in the market society of the electronic age:

The TN-C circuit is of little use as a working ground: the current in the neutral is an electrical noise in itself.
In the event of a zero burnout at the substation, a severe accident occurs: a phase voltage of 380 V appears in the sockets of the house; electrical appliances explode and ignite; a fire breaks out in the house. On the metal cases of electrical installations appears line voltage 220V; hence - massive electrical injuries with deaths.

Power engineers, we must give them their due, perfectly, as professionals, understanding the situation, even during Yeltsin's "democracy" as far as they could, they kept zero. Today, energy supplying enterprises are sufficiently provided with finances for the salaries of specialists and materials for repairs. Cases of burning zero have not been noted for several years.

But the problem of electromagnetic compatibility due to the lack of a working ground remains. Therefore, since 1997, the new SNiP and PUE provide for the supply of apartment buildings according to the TN-C-S scheme. At the same time, each house is supplied with a ground loop, and the protective conductor PE is bred through apartment euro sockets.

How to find out if there is grounding in the house? To do this, you need to open the brownie SCHVS. of this at full legal basis may be required by any owner of a privatized apartment, but the DEZ electrician must open it; you can only watch in his presence. Even if you have a group of access to electrical installations IV or V, giving the right to their sole inspection.

An inspection is enough: if five cable cores come from the substation, you have a TN-C-S system, and you don’t need this article at all. If there were four lived, you have TN-C, and you need to think about how to ground yourself.

Let's say right away: it is unrealistic to make a ground loop for a high-rise building on your own: you need permission from the DEZ, you need an approved project, you need a large amount of earthworks using special equipment on adjoining territory(and if there is a playground?) If the issue is resolved door-to-door, then the only way out is protective zeroing and.

Protective zeroing

As a working ground, protective grounding is only suitable for a washing machine. The microwave from it will only “siphon” more, and the computer will turn off. But at zero, corresponding to the PTB and PUE, it will provide reliable protection.

The protective grounding device is reduced to the supply of a grounding conductor from floor plate to the grounding contacts of euro sockets. It makes no sense to do this yourself: DEZ or RES electricians are willingly and for a small fee to undertake such work (RES - a district of electric networks; a district energy supply enterprise). But if zero (neutral) is rather weak, you also need to install an RCD.

How do you know if your neutral is good? A sure sign of a bad zero is unsystematic voltage fluctuations in the network during stable weather. Or a sudden increase in mains voltage in the evening, at maximum load. If this is observed immediately throughout the house - zero is bad, and RCDs are needed.

More recently, protective grounding was equipped only at industrial enterprises and other facilities where powerful electrical installations are used. To protect their employees from accidental breakdown to the case, each installation and device was grounded without fail. But time does not stand still. Today, our homes are crammed with powerful household appliances: refrigerators, freezers, microwaves, induction cookers, underfloor heating systems and much more. But all this is the source heightened danger. If their isolation is violated, "close communication" with powerful devices can be fatal. That is why, in order to protect all the inhabitants of the home, in country houses it is necessary to equip electrical grounding. Its arrangement can be entrusted to professionals, or you can do it yourself.

Why is protective grounding necessary?

In professional literature, it is indicated that protective grounding is a connection of non-current-carrying parts of electrical installations to the ground (soil), which is performed intentionally. At the same time, in normal condition these parts of electrical appliances and installations are not energized. But if a partial destruction of the insulating layer suddenly occurs, the metal case of the device may be energized.

If you explain in a more accessible language, you will have to remember the school physics course. As we know from this, the current tends to flow in the direction where there is the least resistance. When the insulation is broken on the current-carrying parts of electrical appliances, the current begins to look for a place where the resistance is lowest. So it reaches the body of the device, as a result of which the body is energized. This situation is called "breakdown on the hull". In addition to the fact that the current on the case can harm the device itself or disrupt its functionality, if at such a moment a person or animal touches the device case, they will receive an electric shock. This can have dire consequences.

Protective grounding is performed in order to divert current to the ground (ground). At the same time, it is extremely important to make a ground loop with such low resistance that the current, which is distributed in inverse proportion between the person and the grounding device, passes through the person at the maximum allowable rates, and most of it is redirected to the ground.

What is a ground loop

The most common variant of the ground loop is electrodes buried in the ground, connected to each other in a loop, which can be any geometric figure- triangle, square or other, but also the connection can be made in one row. The arrangement option depends on how convenient it is for installation, and on the size of the territory that can be used for the circuit. Sometimes the ground loop is performed along the perimeter of the building. The resulting design is attached to the shield, for which a ground cable is used.

The distance from the ground loop to the house should not be too large, 4-6 m is considered optimal. You cannot place the loop closer than 1 m to the house, it is undesirable to go further than 10 m.

Important! The ground loop must be equipped below the freezing level of the soil, i.e. at a depth of at least 0.8 m.

The depth to which it is necessary to bury the electrodes depends on the structure of the soil and its saturation with water and can range from 1.5 m to 3 m or more. If a ground water are close to the soil surface, the soil is saturated with water, then the depth will be shallow. Otherwise, you will have to drive the rods deep into the ground or equip another version of the grounding system.

Ground loop from black rolled metal

Any ferrous metal rods can be used as ground electrodes. It can be a steel corner (most often used), a pipe, an I-beam, fittings with a smooth structure. The principle of choice is simple - the convenience of driving into the ground. Those. you can choose any shape, the main thing is that the cross section of the metal is at least 1.5 cm2.

The number of rods - electrodes can be determined empirically or make calculations, but the most common is a triangular ground loop with electrodes at the vertices of the triangle. Between themselves, the rods are connected by metal strips, the same strip leads to the switchboard.

The distance between the rods can be from 1.2 m to 3 m or more. It depends on the resistance of the soil.

Important! Before doing grounding in your home, check with regular electricians in your area. Ask them what are the most common designs, and with what characteristics they equip in your area. At what depth to put the electrodes, how far to take out from the house, what distance to make between the rods. This will make your task much easier.

In addition to the fact that it is possible to equip a ground loop from improvised material, ready-made modular grounding systems have appeared on the market.

The set includes rods made of high-quality steel, they are covered with copper on top. The diameter of the rods is about 14 mm, the length is up to 1.5 m. There is a copper-plated thread on both sides of the rod. The elements are interconnected by means of brass couplings. To deepen the rods into the ground, there are tips that are screwed onto the threaded connection. There are several types of such tips for different soils. The kit also includes clamps for connecting vertical (rods) and horizontal (strips) elements. To protect the structure from corrosion, a special paste is used, which processes all elements of the system.

Ready-made modular grounding systems have several significant advantages:

By connecting vertical elements, a depth of 50 m can be carried out;
The rods are not very susceptible to corrosion due to copper plating and stainless steel;
No welding required;
Arrangement can save space, because. the whole system can be equipped on 1 m2;
Installation does not require special equipment;
Durable.

The choice of grounding system, homemade or ready-made modular, depends only on the financial budget and personal preferences. But in any case, before arranging, it is necessary to make grounding calculations.

How to calculate grounding

For those who do not like unnecessary complications, there is an option to perform grounding empirically. You can equip a triangular circuit at the optimal distance from the house, use metal rods 3 m long, make the distance between the rods from 1.5 to 2 m, connect them together and measure the resistance of the circuit. The requirements for grounding are as follows: the resistance of the ground loop must be in the range from 4 to 10 ohms. BUT general rule- the lower the resistance value, the better. If the measurement result of our circuit does not meet the requirements, then we add more electrodes and connect them with those already installed. We take measurements again. And so we repeat until our circuit has a resistance of 4 ohms.

A more correct solution would still be to make all the necessary calculations before starting the installation of the circuit. The most important thing is to determine the number of required electrodes and the length of the horizontal ground electrode (strip). All this directly depends on the properties of the soil, or rather its resistance.

First of all, we determine the resistance of one rod.

The value of soil resistivity for calculations can be taken from the table.

If the soil is heterogeneous, then its resistance is calculated by the formula:

The value of the seasonal climate coefficient can be taken from the table:

If we do not take into account the resistance of the horizontal ground electrode (strip), then the number of electrodes can be found by the formula:

We find the resistance of spreading horizon. ground electrode:

The length of the grounding conductor is found by the following formulas:

Final number of electrodes:

The demand coefficient can be found from the table:

The utilization factor indicates the influence of currents on each other, which depends on the location of the vertical ground electrodes. At parallel connection electrodes, the currents passing through them affect each other. The smaller the distance between the vertical electrodes, the more resistance the entire contour. That is why it is sometimes advised to space the rods from each other at a distance equal to their length, for example, 3m.

The value of the number of electrodes obtained in the course of calculations is rounded up to a whole number. The calculations are ready, you can proceed with the installation.

How to make grounding in a private house with your own hands

Installation of grounding is recommended to start in the warm season. Firstly, it is easier to carry out excavation work. Secondly, the value of soil resistance will be more accurate and maximum. This is very important for good grounding. And then you can make grounding when the soil is temporarily saturated with water, and its resistance will be 4 ohms, and then drought will come and its resistance will increase to 20 ohms. It is better to immediately take into account the maximum value.

We will consider the arrangement of a ground loop made of rolled metal in the form of a triangle:

First of all, choose a convenient place. We dig a trench in the form of a triangle. The optimal depth is from 0.7 to 1 m, width is 0.5 - 0.7 m. The length of each line is the same as we determined in the course of calculations (the length of the horizontal ground electrode).
From one of the corners (any) we dig a trench leading to the power shield near the house.
Vertical grounding - we drive the electrodes into the vertices of the triangle. You can use a steel corner 50 * 50 or any other rod metal. For the convenience of driving into the ground, we sharpen the end of the rod with a grinder. If the soil is too hard to hammer electrodes into it, then we drill wells.
We deepen the rods so that their top sticks out of the ground. If we had to drill wells, then inserting electrodes into them, we fill them with soil mixed with salt.
We weld a steel strip (at least 40 * 5 mm) to the rods so that a triangle forms. We lead one lane along the trench to the power cabinet.
AT a private house we start the grounding through the shield. To do this, we attach the strip to the ground wire or directly to the power shield with a 10 mm bolt. The bolt must be welded to the strip.

The next step is to check the grounding. To do this, you need the device "Ohmmeter", it costs a lot. In order to check the resistance once or twice in a lifetime, it is expensive to buy it. Therefore, we invite specialists from the energy department to check the resistance of the circuit. In addition to taking measurements, they will also fill out a ground loop passport. If the resistance indicators are normal, then you can bury the circuit. If not, then we drive in additional electrodes.
We fill up the trench. We use for this homogeneous soil without impurities of crushed stone or construction debris.

Important! In dry weather, it is recommended to water the ground loop with water from a hose, so its resistance decreases.

For better operation of the circuit breaker, neutral grounding is also performed. At the entrance to the building, the neutral is connected to re-grounding. The fact is that electricity comes to private homes through the air. For power transmission towers of 6 - 10 kW, the neutral is re-grounded, but for power lines of 0.4 kW, power companies almost never do this. In order for the load to be distributed correctly, it is necessary to re-ground the support near the house (it is desirable that all neighbors are also grounded). And this grounding should not be combined with the circuit.

If you are not sure that you will do everything correctly, you can contact specialized organizations that will perform all the necessary calculations and installation with skill. If you are an ardent business executive who is used to doing everything with his own hands, well, go for it. Just remember - your creation is designed to protect the whole family.

The main element of ensuring the safety of electrical installations is protective grounding. Related systems: automatic protective switches, fuses, lightning protection - cannot function in its absence, and become useless.

What is grounding

This is a complex consisting of metal structures and conductors, which provides electrical contact between the electrical installation housing and the physical earth, that is, with the ground. The system starts with a ground electrode: a metal electrode grounded into the ground. These elements cannot be single; for reliability, they are combined into a ground loop.

How it works

The external ground loop (which is located directly in the ground) is connected using a reliable conductor to the internal loop in the room, or to the ground shield. Next, using internal network protective conductors are connected to the housings of electrical installations, and grounding contacts on switching devices (distribution boards, boxes, sockets, etc.).

Devices that generate electricity also have a grounding system to which the neutral bus is connected. In the event of an emergency (the phase is connected to the body of the electrical installation), there is electrical circuit between the phase conductor and the neutral bus along the ground line. The current in the emergency circuit increases spontaneously, the device trips protective shutdown (circuit breaker) or the fuse is blown.

The result of a working system:

does not ignite power cable(fire hazard);
the possibility of electric shock when touching the emergency housing of the electrical installation is prevented.

The resistance of the human body is ten times higher than the ground resistance. Therefore, the current strength (in the presence of a phase on the body of the electrical installation) will not reach a life-threatening value.

What is grounding

External ground loop. It is located outside the premises, directly in the ground. It is a spatial structure of electrodes (ground electrodes) interconnected by an inseparable conductor.
Internal ground loop. Conductive bus located inside the building. Covers the perimeter of each room. All electrical installations are connected to this device. Instead of an internal circuit, a ground shield can be installed.
Grounding conductors. Connecting lines designed to connect electrical installations directly to the ground electrode system, or to an internal ground loop.

Consider these components in more detail.

External, or external contour

The installation of the ground loop depends on the external conditions. Before starting the calculation and making a design drawing, it is necessary to know the parameters of the soil in which the ground electrodes will be installed. If you have built a house yourself, these characteristics are known. Otherwise, it is better to call surveyors to get an opinion on the ground.

What are the soils, and how do they affect the quality of grounding? Approximate resistivity of each soil type. The lower it is, the better the conductivity.

Plastic clay, peat = 20–30 Ωm m
Plastic loam, ash soils, ash, classical garden soil= 30–40 Ohm m
Chernozem, shale, semi-hard clay = 50–60 Ohm m

This is the best environment to install an external ground loop. Current spreading resistance will be quite low even at low moisture content. And in these soils, the natural humidity is usually above average.

Semi-solid loam, mixture of clay and sand, wet sandy loam - 100–150 Ohm m

The resistance is slightly higher, but with normal humidity, the grounding parameters will not go beyond the standards. If prolonged dry weather sets in in the installation region, it is necessary to take measures to forcibly moisten the installation sites of the ground electrodes.

Clay gravel, sandy loam, wet (permanent) sand = 300–500 ohm m

Gravel, rock, dry sand - even with high overall humidity, grounding in such soil will be ineffective. To comply with the regulations, it is necessary to install deep ground electrodes.

Important! Incorrect calculation of the ground loop, ignoring the parameters, often lead to sad results: electric shock, equipment failure, cable fire.

Many owners of objects, saving "on matches", simply do not understand why a ground loop is needed. Its task, when connecting the phase to the ground, is to ensure the maximum value of the short circuit current. Only in this case, the residual current devices will quickly operate. This cannot be achieved if the current flow resistance is high.

Having decided on the soil, you can choose the type, and most importantly, the size of the ground electrodes. Preliminary calculation of parameters can be performed using the formula:

The calculation is given for vertically installed earthing switches.

Deciphering the formula values:

R0 - the resistance of one ground electrode (electrode) obtained after calculation in ohms.
Req - soil resistivity, see information above.
L is the total length of each electrode in the loop.
d is the diameter of the electrode (if the section is round).
T is the calculated distance from the center of the electrode to the earth's surface.

By setting known data, as well as changing the ratio of values, you should achieve a value for one electrode of the order of 30 ohms.

If the installation of vertical grounding is not possible (due to the quality of the soil), it is possible to calculate the resistance value of horizontal grounding.

Important! Installation of a horizontal circuit is more laborious and is associated with increased material consumption. In addition, such grounding is highly dependent on seasonal weather.

Therefore, it is better to spend more time hammering vertical rods than to follow the barometer and air humidity.

And yet we give the formula for calculating horizontal ground electrodes.

Accordingly, the decoding of additional values:

Rv - the resistance of one ground electrode (electrode) obtained after calculation in ohms.
b - the width of the electrode - ground electrode.
ψ - coefficient depending on the weather season. The data can be found in the table:

ɳГ is the so-called demand factor for horizontal electrodes. Without going into details, we get the numbers from the table in the illustration:

A preliminary calculation of the resistance is necessary not only for the correct planning of material purchases: although it will be a shame if you do not have enough to complete the work, a couple of meters of the electrode, and several tens of kilometers to the store. A more or less neatly drawn up plan, calculations and drawings will be useful for solving bureaucratic issues: when signing documents on the acceptance of an object, or drawing up technical specifications with an energy sales company.

Of course, no engineer will sign papers only on the basis of even beautifully executed drawings. Spreading resistance measurements will be made.

Work technology

We choose the location of the ground electrodes. Of course, not far from the house (object), so that you do not have to lay a long conductor, which will have to be mechanically protected. It is desirable that the entire area of \u200b\u200bthe contour is located in the territory that you control (you are the owner). So that at one fine moment, your protective "earth" is not dug up by a drunken excavator. So we will not hammer the pins behind the fence.

A garden is suitable (with the exception of a potato bed), a front garden, a flower bed near the house. Cultivated areas are preferred, they are regularly watered. And additional moisture in the ground will benefit grounding. If your soil has low resistivity, you can install grounding on the site, which will then be covered with asphalt or tiles. Under artificial turf, the earth does not dry out. And the risk of damaging the ground loop is minimal.

Of course, it is necessary to take into account future plans. If a garage with a viewing hole appears at the installation site of the circuit in a year, it is better to immediately choose a quieter place.

Depending on the shape of the site, we choose the order of the electrodes: in a line, or in a triangle.

Important! Regardless of the location, there must be at least three vertical ground electrodes.

If a triangle is selected, we mark out a platform of the appropriate shape with sides of 2.5–3 meters. We dig a trench in the shape of an equilateral triangle to a depth of 70–100 cm, a width of 50–70 cm. We know that all ground electrodes are interconnected. The conductor must be deepened to a distance of at least 50 cm, taking into account the minimum ground level (for example, digging up beds). If a coating is laid on top, its thickness is not taken into account. Only clean soil.

You can select the entire soil, not only along the perimeter of the trench. A triangular pit with a depth of 0.7–1.0 m will be obtained. The finished contour can be covered with soil with low resistivity. For example, ash or ashes. Salts will penetrate into the ground, and will help reduce the overall resistance to current spreading.

After that, at the corners of the pit (trench), we begin to clog the electrodes.

Grounding parameters (we consider the vertical arrangement)

Steel without galvanized coating:

Circle - diameter 16 mm.

Pipe - diameter 32 mm.

Rectangle or corner - cross-sectional area 100 mm².

Steel galvanized

Circle - diameter 12 mm.

Pipe - diameter 25 mm.

Rectangle or corner - cross-sectional area 75 mm².

Circle - diameter 12 mm.

Pipe - diameter 20 mm.

Rectangle or corner - cross-sectional area 50 mm².

The soil must be tight metal surface ground electrode. It is forbidden to paint the electrodes!

But what if, according to calculations, the length of each of the three electrodes exceeds 1.5–2 meters? There are little secrets.

We connect the electrodes with a conductor. If the reinforcement is steel, welding is best. Copper rods are connected with a bolted tie, the conductor must have a cross section of at least 30% of the cross section of the electrodes.

After assembling the circuit, we measure the resistance to current spreading. Requirements for the ground loop for individual housing - 10 ohms. It is better to entrust the measurement to certified specialists who have the appropriate equipment. Moreover, when receiving technical specifications from power engineers, you still have to provide a grounding system for measurements. If the resistance is above the norm, add electrodes and weld them to the circuit. Until we get the norm.

Ground loop inside the object

As a rule, this is a steel tire laid in an open way along the inner surface of the walls, near the floor.

In individual residential buildings, the installation of an internal ground loop is not carried out. Due to the low hazard class of the premises, and a small number of electrical installations. Instead of an internal circuit, a grounding shield, or main grounding bus (GHSh), is installed.

The shield is connected either to the internal circuit (as in the illustration), or with the help of a conductor to the external ground circuit. Protective ground conductors are routed directly from the shield to electrical installations. Often, instead of the grounding shield, the “PE” terminal block can be used directly in the entrance shield of the apartment.

Outcome

We examined in detail what a ground loop is, why it is needed, and what it should be like according to the PUE. Self-installation does not reduce responsibility: your life and the lives of household members depend on compliance with safety requirements.

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General requirements

Grounding is one of the main measures of protection against damage. electric shock.

This article provides detailed step-by-step instruction 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- it's deliberate electrical connection any point of 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 earthing switches) and metal rods or metal strips that, by welding, connect vertical ground electrodes (the so-called horizontal earthing switches).

Vertical and horizontal grounding together form ground loop, this contour can be closed (Figure 1) or linear (Figure 2):

The ground loop must be connected to the main ground bus in the introductory electrical panel of the house using ground conductor which, as a rule, uses the same metal strip or rod that is used as a horizontal ground electrode.

The protective grounding of a private house will have the following general form:

In turn, the combination of the ground loop and the ground conductor is called grounding device.

A closed ground loop is usually made in the form of a triangle with sides from 2 to 3 meters (depending on the length of the vertical ground electrodes); it is important that the distance between the vertical ground electrodes is not less than their length (see Fig. 1). A closed contour can also be made in other shapes, such as an oval, a square, etc. In turn, the linear circuit is a series of vertical earthing switches in the amount of 3-4 pieces lined up in a line, while, as in the case of a closed circuit, the distance between them in the linear circuit must be at least 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 earthing switches must be made of black or galvanized steel or from copper (clause 1.7.111. PUE). Due to their high cost, copper ground electrodes, as a rule, are not used. Same way earthing conductors from reinforcement should not be made - the outer layer of the reinforcement is hardened, which disrupts the distribution of current over its cross section, in addition, it is more susceptible to corrosion.

Vertical earthing switches are made of:

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 grounding should be 2-3 meters(recommended at least 2.5 m)

Horizontal earthing switches are made of:

round steel rods with a minimum diameter of 10mm (recommended: 16-20mm)
steel strip dimensions 4x40

The ground conductor is made of:

round steel rod with a minimum diameter of 10mm
steel strip with dimensions of at least 4x25 (recommended 4x40)

2. Grounding installation procedure:

STEP 1- Choose a place for installation

The place for installation is chosen as close as possible to the main electrical panel (introductory panel) of the house in which the main ground bus (GZSH) is located, it is also a PE bus.

If the input electrical panel is located inside the house or on its outer wall the ground loop is mounted near the wall on which the electrical panel is located, at a distance of about 1-2 meters from the foundation of the house. If the electrical panel is on a support overhead line power lines or on a remote rack, the ground loop can be mounted directly below it.

At the same time, ground electrodes should not be located (used) in places where the earth dries out under the influence of heat from pipelines, etc. (p. 1.7.112 PUE)

STEP 2- Excavation

We dig a trench in the shape of a triangle - for mounting a closed ground 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 the convenience of welding 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

We place vertical ground electrodes in trenches at the required distance from each other (1.5-2 meters), after which we drive them into the ground using a perforator with a special nozzle or an ordinary sledgehammer:

Beforehand, the ends of the ground electrodes must be sharpened for easier entry into the ground:

As already mentioned above, the length of the vertical ground electrodes should be approximately 2-3 meters (at least 2.5 meters is recommended), while it is necessary to drive them into the ground for the entire length, so that the upper part of the earth electrode protrudes 20-25 cm above the bottom of the trench :

When all vertical ground electrodes are hammered into the ground, you can proceed to the next step.

STEP 4— Installation of horizontal grounding switches and grounding conductor:

On the this stage it is necessary to interconnect all vertical grounding conductors with the help of horizontal grounding conductors and weld a grounding conductor to the resulting ground loop, which will come out of the ground to the surface and is designed to connect the ground loop to the main grounding bus of the input electrical panel.

Horizontal and vertical grounding conductors are interconnected by welding, while the junction must be welded on all sides for better contact.

IMPORTANT! Bolted connections are not allowed! Vertical and horizontal grounding conductors forming a grounding loop, as well as a grounding conductor at the point of its connection to the grounding loop, must be connected by welding.

Welds must be protected from corrosion, for which the welding points can be treated with bituminous mastic.

IMPORTANT! Myself the ground loop must not be painted!(clause 1.7.111. PUE)

The result should be something like this:

STEP 5- We fill the trench with soil.

Everything is simple here, we fill up the trench with the ground loop mounted, so that there is at least 50 cm of soil above the loop, as already mentioned above.

However, there are some subtleties here:

IMPORTANT! The trenches for horizontal grounding conductors must be filled with homogeneous soil that does not contain crushed stone and construction debris (clause 1.7.112. PUE).

STEP 6- Connecting the grounding conductor to the GZSH of the input switchboard (input device).

Finally, we have come to the final stage - grounding the electrical panel at home, for this we perform the following work:

We bring the ground conductor to the electrical panel, so that about 1 meter remains before the electrical panel, if the input shield is in the house, it is advisable to bring the ground conductor into the building. At the same time, the following identification mark should be provided at the places where grounding conductors are entered into buildings (clause 1.7.118. PUE):

The grounding conductor itself, located above the ground, 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 ground bus, which should be used as a bus inside the input device (input switchboard at home). RE(clause 1.7.119. PUE).

IMPORTANT! The main ground bus should usually be copper. It is allowed to use the main earthing bar made of steel. The use of aluminum tires is not allowed. (clause 1.7.119. PUE).

As a result, the grounding circuit of the shield at home should look like this:

NOTE: the given grounding diagram of the electrical panel refers to .

The following protection devices are installed in this electrical panel:

1 - - to protect electrical wiring from short circuits and overloads.

A lot has already been said about how important a properly installed grounding system is for a private house or cottage. Therefore, there is no particular need to repeat the danger of electric shock in a house that is not connected to a ground loop. And if you want to ensure the safety of your living space to the maximum, then the information presented in this article will no doubt be useful to you.

Types of grounding for a private house

Depending on the design features power lines suitable for the house are used various systems grounding. The following varieties are distinguished: TN-S, TN-C, TN-C-S, TT, etc. Private houses and cottages are usually connected to two types of grounding systems: TN-C-S and TT. And if your home is missing, then it is these systems that are easiest to implement in practice, it is them that many craftsmen create on their own, and it is about them that this article will be discussed.

Briefly explain what the letters in the name of the systems mean:

The first character indicates the grounding parameters on the power supply (T - ground, etc.).
The second character (N or T) characterizes the grounding parameters of open parts of home electrical installations. The letter N, for example, means grounding or connecting the protective conductor of a home electrical installation to the neutral of the power source (transformer substation).
The letters S and C denote a subspecies of the system in which grounding is done through the power supply.

Simply put, if the letters TN are the first in the designation, then we are talking about a system with deaf grounding of the power source, and the consumer's electrical system is connected to its neutral by means of neutral and protective conductors. As we have already said, grounding systems come in several varieties:

TN-C is a system with combined neutral and protective conductors. The supply line in this case consists of two or four-core cables (phase and neutral conductors - in a single-phase power supply system, three phase and one zero - in a three-phase power supply system). The TN-C system can hardly be called a full-fledged grounding system, because the grounding conductors of the electrical installation in it are connected to the neutral wire coming from the transformer. Usually it is called zeroing, because it is hardly capable of performing all the functions of a ground loop.
TN-S is a system with separated neutral and protective conductors. The supply line in this case consists of three- or five-core cables (phase, neutral and protective conductors - in a single-phase power supply system, three phase plus neutral and protective conductors - in a three-phase power supply system).
TN-C-S is a system in which the neutral and protective conductors combine their functions only in a certain area, which starts near the power source and ends at the entrance to the house. Here they are also divided into zero protective (PE) and zero working (N) wires (the protective conductor in such a system is re-grounded). In fact, the TN-C-S system is created on the basis of TN-C.
TT is a system in which home system power supply has a separate deaf grounding, which is not connected in any way to the grounding of the supply substation.

Grounding in all TN category systems is carried out through transformer substation, while the TT system involves the creation of a ground loop directly near the house. You can argue for a long time about which of the two systems is better - TN-C-S or TT, so we will immediately indicate the pitfalls of these two systems.

If you are thinking about creating TN-C-S systems, then first of all you should make sure that the power line that supplies electricity to your home is reliable. After all, the state of suburban power lines (and they are, in most cases, air) leaves much to be desired. No one will guarantee that one fine day, as a result of an accident on the line (if a flimsy support, etc., tilts under its weight), the bare neutral wire will not connect to the phase wire. As a result, zero will burn out from the transformer, and we will get a deadly voltage that “walks” along the body of household electrical appliances.

AlexeyL FORUMHOUSE User

For the TN-C-S scheme, you must either be completely confident in the safety and reliability of the PEN conductor coming to you down the street, or you must guarantee this safety by your own grounding. In the typical state of local air networks, one can only be sure of the opposite: the unreliability of the PEN. And the construction of a ground that can withstand the zero current of many neighbors in the event of a neutral break and a large phase imbalance of loads is a very difficult and expensive task.

Let us explain: PEN is a combined working zero (N) and protective zero (PE) conductor connecting a transformer substation with an introductory home shield.

The use of SIP cable as part of the supply line provides some security guarantees, but with the unsatisfactory condition of the ground supports, all these guarantees can be called into question. Simply put, it is possible to create a TN-C-S type grounding system only if you have complete confidence in the reliability of the supply line.

The TT system in a private house also has its drawbacks. Systems of the presented type require the mandatory presence of RCDs or dif-automats in the grounding circuit, which should be regularly checked for operability. To ensure safe operation, the CT must be equipped with potential equalization systems and an artificial ground loop, the creation of which requires time, effort and certain costs.

In practice, the creation of a TN-C-S system always looks more preferable, but with a dubious state of the current supply lines (the supply line is formed by bare conductors, its frequent breaks are observed, aerial supports are in an unsatisfactory condition, etc.) as a more reliable alternative, it is recommended to create a TT system.

Briefly about the TN-S system

If a TN-S system is connected to the house, then it is enough to equip the inlet shield with a grounding bus, to which the PE inlet ground conductor and protective conductors going to household consumers should be connected. The PE conductor can be connected to a repeated ground loop. We will return to the question of how to do this.

AlexPetrow FORUMHOUSE User

With TN-S, a five-wire line with separate PE and N comes to the consumer. In such a system, nothing needs to be divided.

We are talking about the division of the incoming neutral wire, which is supplied to the consumer in TN-C systems and is divided when creating the TN-C-S system. A similar division is shown in the diagram.

TN-C-S system design

If the TN-C system is suitable for your home, if you have verified the impeccable condition of the supply line and made sure that the SIP cable is used as the supply conductor, you can begin to create a TN-C-S type grounding system.

The separation of the conductor into a protective conductor PE (having a yellow-green color) and a zero one (has a blue color) is carried out in the input shield.

In the shield, re-grounding is connected to the system.

In accordance with the updated edition of the PUE rules, the separation of the PEN conductor must be carried out before the introductory switching protective device and before the electric meter. It is strictly forbidden to include protective and switching devices in the circuit of PEN and PE conductors. You can only break the conductor circuit N (PUE 1.7.145).

AlexPetrow

PEN and PE conductors are inseparable! All switching devices (automatic switches, knife switches, packet switches, metering devices, etc.) must be located on the N conductor line (it can be "torn" and sometimes necessary).

Separation of the PEN conductor is carried out according to the following scheme:

For separation, two buses should be used: the main grounding (GZSH) and zero (N). The main grounding bus is connected to an additional grounding circuit through the shield body, and is also connected to it. input cable PEN and connect the ground terminals of the sockets installed in the house. The following are connected to the N bus: an electric meter, circuit breakers and power terminals of home energy consumption points.

The main ground bus becomes the PE bus after the jumper connecting the GZSH and N. It is to PE that an additional ground loop and protective conductors are connected to the ground terminals of the sockets.

AlexPetrow

In fact, physically and organoleptically there should be two tires - PE (GZSH) and N. PEN is divided according to the "rule of the Russian letter H" - this is how the correct division looks like. The supply PEN can come to either end of the vertical bar (bus), and this dash after the jumper will always be PE. The other vertical line will always be N (all the way). A jumper is just a jumper. PE is grounded, and protective conductors will be switched on this bus, and N serves as a load current conductor. After separation, they should not be connected.

The separation is more clearly shown in the photo.

In accordance with the rules of the PUE, it is recommended that the main ground bus be made of copper. The use of steel tires is allowed and the installation of aluminum tires is strictly prohibited. GZSh and N tires are made from the same material.

stanislav-e88a FORUMHOUSE User

Zero (N) from the separating bus goes to a 2-pole input machine, then to the counter. From the counter zero - to consumers. Double automata are not needed (except for the introductory one). PEN must be divided before it. Everything is simple with the phase: it goes to the introductory machine, then to the counter, then to consumer groups.

The main requirements for the PEN conductor separation unit are as follows:

The zero separating bus N must be installed on an insulator without fail, that is, it must be isolated from the shield body, to which the PE bus is additionally connected (after all, after separation, these two buses should not touch anywhere);
All conductors suitable for separating busbars must be fastened with strong bolted connections, which ensures reliable connection and the possibility of detaching individual conductors;
The cross section of the GZSH must be greater than or equal to the cross section of the supply conductor PEN.

It is recommended to use specialized wires as protective PE conductors. If PE conductors and phase conductors are made of the same material, then the dependence of the minimum PE cross section on the phase conductor cross section will be as follows.

The sign "£" in this case means - "≤".

If the protective and supply conductors are made of different materials, then the PE cross section should be equivalent in its conductivity to the cross section of the phase wires discussed in the table.

The minimum cross-section of a matched conductor in a TN-C system must comply with the following values: 10 mm² for copper conductors and 16 mm² for aluminum. If the cross section of the conductor is smaller, then it is forbidden to separate it! In this case, you should resort to the creation of a TT system.

Re-Earthing and Residual Current Devices in TN-C-S Systems

If you want to protect yourself and your family as much as possible from leakage currents, then the TN-C-S grounding system should be equipped with residual current devices (RCDs) or differential circuit breakers. In accordance with the recommendations of the updated edition of the PUE (ed. 7), TN-type systems equipped with residual current devices (RCDs) must be connected to re-grounding, which is mounted at the entrance to the house.

SB3 FORUMHOUSE User

Re-grounding is required at the ends of overhead lines and branches from them longer than 200 m, as well as at the inputs of overhead lines to electrical installations, in which, as a protective measure against electric shock during indirect contact, a protective automatic power off is performed.

If RCDs are not used in your system, and there is already re-grounding within 200 m from your shield, then there is no special need to create additional grounding at the entrance to the house.

Crazy cat FORUMHOUSE User

If there is already a re-grounding at a distance of 200 m from the input, or the input is made by a cable laid in the ground, there is no need to re-ground.

About RCD: for additional protection from leakage currents when indirectly touching the open surfaces of electrical appliances in general scheme power supply, it is recommended to introduce residual current devices (RCD) or differential circuit breakers. Such protection works on weak leakage currents, turning off the mains power (leakage currents, despite their small value, can be dangerous to humans). Their installation is advisable for the reason that conventional circuit breakers operate only on short-circuit currents.

In modern systems, it is customary to install RCDs of two different ratings: a general fire RCD that operates on a leakage current of 100 mA, as well as one (or several) RCDs connected to the line of plug sockets and triggered by a current of 30 mA or 10 mA.

RCD connected to household appliances, directly interacting with water (washing machines and dishwashers, water heaters, etc.), should respond to a leakage current of 10 mA. RCDs are not installed on the line of lighting systems.

As a result, we will have such a scheme.

The function of protection devices or differential circuit breakers must be checked regularly (once a month, etc.). To do this, there are special buttons on the body of the devices - “test”.

Re-grounding involves connecting the housing of the input shield to the ground loop.

In accordance with the rules of the PUE (clause 1.7.102) in networks alternating current voltage up to 1 kV as a repeated ground loop for TN-C-S systems, you can use underground structures of electrical poles, metal water pipes, ground loops of lightning rods, etc. These elements should be used first. If this is not possible, then an artificial contour is created.

In networks direct current earth conductors must be connected to an artificial earth loop, which must not be connected to underground pipelines.

We will return to the question of the design of an artificial ground loop.

The cross section of the conductors connecting the shield and the ground loop in networks with a solidly grounded neutral and with voltage up to 1 kV must comply with the following parameters.

If an aluminum conductor is used, its area must be at least 16 mm².

Potential equalization system

After creating a grounding system equipped with automatic shutdown devices, a protective conductor appears in the house, connecting all elements of the power supply system. This conductor poses a potential threat. After all, if any consumer is damaged, a dangerous potential is transferred to the body of all undamaged electrical appliances. He will be present there until the RCD is triggered, creating a danger with direct contact. In order to reduce the specified voltage in the building, it is necessary to create a potential equalization system (PSE) capable of equalizing the potential of all its conductive parts (building structures, utilities, etc.).

ASZyuzin1950 FORUMHOUSE User

The potential equalization system is not an independent measure of protection, but its presence when using automatic power off is mandatory.

The SUP is a kind of grid of conductors (PE), which unites all the current-carrying elements of the object through the GZSH, that is, through its PE part. The connection of the PE busbar and the conductive parts of the building is made radially (a separate PE conductor is connected to each grounded structure). You can find out more in the corresponding FORUMHOUSE section.

TT grounding system in a private house

If you have come to the conclusion that it is not advisable or dangerous to connect a TN-C-S system to your home, then the only alternative that allows you to ensure your own safety is to create a TT system. Her scheme is as follows.

As you can see, the GZSH and grounding conductors are nowhere connected to the input PEN conductor and the neutral wire - N.

The use of RCD protection devices or differential circuit breakers as part of a TT system is a prerequisite for its safe operation. The operating characteristics of the protective devices in this system correspond to the RCD parameters for TN-C-S systems.

Also, in TT systems, the main potential equalization system (OSUP) should be created. Ideally, the BPCS is created complete with an additional system (DSUP).

If the TT system is connected to a metal shield, then all conductors in the shield must be double insulated. As an alternative to metal shields, plastic shields can be used.

AlexPetrow

The metal shield is grounded. We make double insulation in the shield and take precautions against direct and indirect contact (the neutral bus will be in an insulating box, etc.). If the shield is plastic - even better (there are some for the street).

For more reliable insulation of conductors at the points of their passage through the body of the metal shield, special textolite bushings can be used.

GZSH using copper wire connected to a conductor leading to an artificial ground loop. In the shield, PE conductors are connected to the ground bus, coming from domestic consumers and from potential equalization systems.

It is advisable to make underground elements connecting the ground loop with the shield from steel (from a strip). The use of bare aluminum conductors in this case is prohibited.

Calculation and creation of a ground loop

As is known, the dangerous potential that arises in protective conductor PE at breakdown phase voltage on the housing of the home appliance, directed to the area with the least resistance. And in order for the voltage to continue to go into the ground when a person touches the open parts of the electrical installation, protecting people from electric shock, the ground loop must have low resistance. Therefore, the calculation of the ground loop is reduced to determining the resistance to the spread of currents on the grounding device. This indicator depends on several factors:

From the area of grounding elements.
from the distance between them.
From the depth of their immersion in the ground.
From the conductivity of soils.

For TT grounding systems installed in networks with voltage up to 1 kV and equipped with protective devices RCD, PUE rules (clause 1.7.59) establish the following dependence: RaIa<50 В. Где:

Ia - minimum RCD setting current (in our case, it is 10 or 30 mA);
Ra is the total resistance of all elements of the grounding system.

In accordance with the formula, for an RCD with a setting of 30A, this figure should not exceed - 1660 ohms (the minimum requirement for a TT system). Such values, regulated by the rules of the EIC, can be misleading. Therefore, in practice, many people strive to achieve a ground loop resistance that does not exceed 4 ohms (which meets the requirements for a power supply ground loop).

human FORUMHOUSE User

I was able to drive 6 electrodes of 1.5 m into one point, but Makita, taken from work, helped me. Driven 0.2 m below the zero level. I did not measure the ground resistance, but the practice of using such electrodes as ground electrodes shows that an electrode 9–10 m long gives less than 4 ohms on our soils.

If you are in doubt about the number and length of electrodes, then it is best to contact specialists to calculate the ground loop. Also, these parameters can be obtained from neighbors who have a valid ground loop, approved by the supervisory authorities for operation after carrying out the appropriate resistance measurements.

The electrodes can be placed both in a row and at the corners of geometric shapes (at the corners of a triangle, etc.). In each case, their location is determined by the convenience of installation work and the availability of free space.

The distance between the electrodes is determined by the rod utilization factor, which is -2.2. That is, in order for the system to work with maximum efficiency, the distance between two identical electrodes must be no less than 2.2 times the length of each of them (in all directions). With a decrease in this distance (and in practice it most often happens), the efficiency of the system will decrease.

Before starting the installation work, the top layer of soil is removed, and then, at the marked points, the electrodes are clogged.

The upper ends of the electrodes are tied with a strip or steel bar and connected by welding.

At the final stage, the ground loop is connected to the electrical panel.

All connections in the construction of the ground loop must be made by welding.

For those who want to learn more, there is a topic on our portal dedicated to this issue. You can learn how to produce and how, based on the practical experience of FORUMHOUSE users. In the video - how to