Artificial grounding: types, functions, requirements and installation

What acts as an artificial grounding conductor

The grounding element is made in the form of a conductor (electrode) of a certain material, which is placed in the ground.
In some cases, several similar grounding conductors are installed. Determining the situation when it is necessary to install a group of artificial rods is realized through special calculations. The result of the calculation justifies the choice of electrode configuration in relation to its resistance - the main indicator that determines the quality of grounding.

An artificial ground electrode is made from the following materials:

Copper-plated steel. The connection between copper and steel has good adhesion. The rods are durable and have excellent contact with any materials. Due to its chemical properties, the alloy has excellent electrical conductivity. The electrochemical activity of copper and steel is insignificant; normal operation of ground electrodes made of such metal can reach more than a hundred years.
Cink Steel. Advantages: corrosion resistance of the material, low resistance, electrodes are resistant to acidic environments.
Black metals. Disadvantage: rapid destruction in aggressive soil (corrosion and rust form). The high strength of the material increases the resistance to current spreading, which is extremely dangerous for humans.

In addition to the material, artificial ground electrodes differ in shape and location in the soil (deep vertical and extended horizontal type).

DIY grounding installation

The location is chosen so that there are no communications on the site. Before making grounding at the dacha with your own hands, coordinate the scheme with the water supply, gas service and other offices. Grounding is done more often on the north side of the house, since there is always a more humid place on the site.

Mount the circuit according to the rules:

dig a trench for horizontal connections;
pins are hammered into the corners of a triangle with equal sides;
You cannot dig holes for the rods; the rods must fit tightly into the ground;
weld the strip to the corners, attach a conductive cable going to the building;
After joining, welding areas are treated with melted bitumen (resin);
bury the installation site.

Check grounding using a multimeter. The socket is opened in the house, the device is switched to voltage regulation. After connecting the zero and phase probes, the multimeter should show voltage. Then the phase and ground are connected, and the voltage should drop slightly.

PUE REQUIREMENTS FOR THE ARRANGEMENT AND QUALITY OF GROUNDING

To implement such protection against electric shock, it is necessary to ensure reliable contact of the electrical installation housing with the ground.

In its presence, a current charge dangerous to humans flows into the ground through a grounding device, the resistance of which is significantly lower than that of the human body.

TYPES OF GROUNDING DEVICES

According to the requirements of the PUE, electrical equipment enclosures must be grounded to ensure safety. For this purpose, various types of grounding conductors are used.

The following can be used as ready-made ones:

metal structures laid in the ground and in direct contact with it;
metal casings and sheaths of cables laid in the ground for specific purposes;
metal pipelines (except for gas communications and oil pipelines);
railway rails.

The use of ready-made structures as grounding conductors significantly simplifies and reduces the cost of arranging the entire system.

Specially mounted grounding devices are used when it is not possible to use underground pipes, cable communications or metal structural elements.

They are various structural elements placed in the ground at a certain depth and ensuring reliable contact with the soil.

The simplest version of such a ground electrode is a steel rod at least 2.5 meters long. After it is buried, a thick copper conductor (steel strip) is attached to the tip and connected to the grounding system.

GROUNDING RESISTANCE

The main requirement for a grounding device, regardless of its type, is to provide conditions for the flow of charges dangerous to humans into the soil. Its functionality is assessed by its spreading resistance (the lower it is, the more effective the grounding is).

The main components are resistances:

the ground electrode itself;
transitional (contact) between the ground electrode and the ground;
soil at the point of contact with the grounding device.

According to the PUE, the resistance of a typical device installed on the consumer side should not exceed 30 Ohms. Under special operating conditions of equipment (at power substations, in particular), it is standardized at a level of no more than 4 ohms.

It is possible to achieve standardized indicators by taking special measures. As a rule, they come down to the following techniques:

increasing the contact area of artificial grounding elements with the ground;
improving soil conductivity (by moistening or adding chemicals).

In addition, the requirements of the PUE require periodic measurements of grounding resistance for compliance with current standards.

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Design features

As mentioned above, the basic design element is the grounding rods. Their number, material, diameter and length depend on the installation conditions and the soil resistivity to current spreading. The higher the resistance, the greater the total length and/or diameter, the greater the number of installation points for grounding electrodes.

The rods have threads at the ends and are connected to each other by means of couplings. At the same time, to ensure better conductivity in the places where they are installed, the constructs are lubricated with conductive lubricant (paste).

Foreign manufacturers use a trunnion-type couplingless connection; it is more contact and does not need to be lubricated with paste. That is, a self-closing structure is obtained (the example below shows a cut at the junction).

To facilitate installation in the ground, the kits include tips and impact heads. Manufacturers from Russia make these components with threads, while foreign ones eliminate the risks arising from threaded contact, especially when hammering, and connect the elements securely into a joint.

At the point where the last (upper) grounding conductor exits, the entire structure is connected using a clamp to a lightning protection system or grounding bus

The geometry of the clamp does not matter (diagonal or cross), it is only important that its material, in terms of corrosion, does not “conflict” with the material of the grounding conductors and grounding conductors

Resistance measurement

The final stage of installation of the structure is to measure the resistance of the electrodes.
This parameter is the main qualitative characteristic of the operation of an artificial type grounding loop. It depends on factors such as the area of the electrodes and the electrical resistivity of the soil. Resistivity shows the level of electrical conductivity of the soil, acting as a conductor. It varies in different soils; its value is influenced by humidity, temperature, composition and density of the soil, as well as the presence of salts, acidic and alkaline residues in it.

The resistance of the installed circuit is checked using special equipment. If the system contains branches, then first take measurements on individual sections of the main line and compare them with the indicators on the section connected to the ground electrode. After this, readings are taken between grounded electrical installations and correlated with the readings in previously checked areas.

Grounding Requirements

After you have figured out what is the definition of the very concept of grounding, you can move on to those categories and norms that are introduced by current standards. According to the PUE, the grounding device is primarily subject to the following requirements:

the purpose of the charger is to effectively drain dangerous currents into the ground, for which purpose their design includes a whole set of conductors and metal rods;
All parts of the electrical installation, including metal switchboard doors, must be grounded;
the total contact resistance of the contacts in the grounding system should not exceed 4-30 Ohms;
when installing it in distributed loads, it is necessary to use a potential equalization system (its purpose is to eliminate uneven voltage distribution).

Additional information: Since the main purpose of grounding is to ensure the safety of personnel working with the equipment, during its operation special attention is paid to the reliability of operation. The quality of its work is ensured by a whole range of preventive measures and periodically organized tests.

Grounding and grounding.

Main functions

In electrical engineering, concepts such as working and protective grounding are used. Working grounding is used to ensure efficient and uninterrupted operation of the installation. Lightning rods that protect electrical installations from celestial electricity and fires also belong to the category of workers, since in this case grounding does not protect against electric shock.

To protect a person from electric current or lightning strike, protective grounding is used. In other words, protective grounding is performed to reduce the touch voltage to a safe level. This is especially important on electrical equipment with high, life-threatening voltage. The ground electrode is part of the grounding device (grounding, charger). It is in close contact with the ground. One end of it is connected to an electrical appliance, due to which the potentials of the device and the ground are equalized, and this protects against electric shock.

According to clause 1.7.28 of the PUE, grounding is an intentionally made electrical connection of a power supply point, electrical installation or equipment with a grounding device. Grounding is connected at all electrical installations.

Types of designs

Using incorrectly connected electrical appliances can be unsafe. The danger is that during use a breakdown may occur, as a result of which the voltage will transfer to the device body. This voltage can either damage the device itself or cause electrical injury of varying severity to a person (including death). To prevent such problems, two types of grounding can be used:

Natural. This includes massive structures that are permanently in the ground. The role of natural grounding conductors is given to the foundations of buildings, water pipes, metal structures and sheet piles, well fixed in the ground. The advantage of such structures is that providing grounding with their help does not require additional costs. However, natural loop resistance cannot be calculated.
Artificial. Grounding of this kind is created specifically from horizontal and vertical elements (electrodes) made of a certain material and having a specific size. The main elements of the artificial contour are most often steel parts that have a round or angular shape. The quality of such grounding depends on the resistance possessed by artificial ground electrodes. The resistance of each electrode is determined using a special formula.

All modern devices powered by electricity are grounded. All that needs to be done is simply to provide a connection to the main grounding system.

conclusions

The PUE's recommendation on the electrical connection of all grounding loops in a building is justified and, if implemented correctly, not only does not create a danger to complex electronic equipment, but, on the contrary, protects it. In the event that the equipment is sensitive to lightning interference and requires its own separate grounding electrode, a separate process grounding can be installed in accordance with the manual supplied with the equipment. The potential equalization system, which combines disparate grounding loops, must ensure a reliable electrical connection and largely determines the overall level of electrical safety at the facility, so special attention should be paid to it.

What are the requirements for artificial grounding conductors?

Artificial grounding conductors cannot be painted, since painting acts as an insulator and prevents the discharge of electric current into the ground. Thus, the color of the grounding conductor should be the natural color of the metal used in grounding devices. But the connection points of the conductors (welding seams) must be painted with bitumen paint to prevent destruction.

You cannot place artificial or use natural grounding electrodes near heat sources that dry out the earth. For arid areas there is a special reinforced concrete structure. The ground electrode is made in the form of a container and placed below the surface of the earth. The container is filled with water through the hatch. Thus, the water distribution system takes part in grounding. Steel electrodes are connected to the outlet from the container. This ensures optimal resistance.

To create artificial grounding conductors, the following materials with the specified parameters are used:

the diameter of the steel reinforcing bar is at least 10 mm;
the diameter of the galvanized rod is at least 6 mm;
in the corners the wall thickness is from 4 mm;
when using strip steel, its thickness must be at least 4 mm;
in lightning protection grounding conductors, the cross-section is taken from 155 mm2;
The wall thickness of rejected pipes is at least 3.5 mm.

Only for temporary electrical installations can electrodes with minimum values be used. In order for the grounding device to serve for 40-50 years in favorable soil conditions, it is enough to select rods for it that are 2-3 mm larger. In wet soils, the thickness and diameters of the pads should be 2 times higher than the minimum.

Of all the mentioned materials, the use of round reinforcement is considered the most optimal, since the metal consumption in this case is reduced by 1.5 times, and the cost of grounding devices is correspondingly reduced.

The corrosion resistance of round steel is higher than that of linear steel, because the round electrode has the smallest contact area with the ground compared to other forms of electrode. Another advantage is that round rod electrodes are easier to install, saving time spent on charging devices.

When grounding powerful high-voltage installations, circuits are used consisting of horizontal beams extending over hundreds of meters and several dozen vertically installed rods. To prevent artificial ground electrodes from shielding each other, the beams are spread horizontally in opposite directions. If there are 3 or 4 rays, they are placed at an angle of 90 and 120 degrees, respectively.

Deepening the electrodes

The electrodes are driven into the ground by driving them with a sledgehammer. To make work easier, it is better to use a scaffold or stepladder. If the metal of the electrodes is too soft, then the blows are delivered through special wooden bars. There is no need to drive the pins in completely: about 10-20 centimeters should remain above the ground, which are used to connect to the circuit.

The factory electrodes are driven in with a jackhammer. After the pin is deepened, a coupling and an additional grounding conductor are screwed onto it. The process is repeated several times until the required depth is achieved.

Types of grounding

In the classification of types of grounding there are two main types:

Working.
Protective.

There are several subgroups: radio grounding, measuring, instrumental, control.

Working

There is a certain category of electrical installations that will not work unless they are grounded. That is, the main purpose of constructing a grounding system is not to ensure operational safety, but to ensure the operation itself. Therefore, in this article we will not be interested in this species.

Protective

But this type is specially arranged to ensure the safety of electrical installations. It is divided into three categories depending on its purpose:

Lightning protection.
Protection against surge voltage (overload of current consumption line or short circuit).
Protection of the electrical network from electromagnetic interference (most often this type of interference is generated from nearby operating electrical equipment).

We are interested in pulse overvoltage. The purpose of this type of grounding is the safety of operating personnel and the installation itself in the event of an accident or equipment breakdown. Typically, such a breakdown inside an electrical unit is a short circuit of the electrical circuit wire to the device body. The short circuit can occur directly or through any other conductor, for example, through water. A person who touches the installation body is exposed to electric current, because he becomes its conductor into the ground. In fact, it itself becomes part of the ground loop.

Grounding diagram in a private house

That is why, in order to eliminate such situations, the housing is grounded to a circuit located in the ground. At the same time, the activation of the grounding circuit is an impetus for the system of automatic machines, which immediately turn off the power supply to the equipment. All this is located in special power and distribution boards.

Ground resistance

There is such a term as resistance to current flow. For ordinary people it will be easier to perceive it as resistance to grounding. The whole point of this term is that the grounding circuit must work correctly within certain parameters. So resistance is the main one.

The optimal option for this value is zero. That is, it is best to use materials for assembling the circuit that have the highest electrical conductivity. Of course, there is no way to achieve the ideal, so try to choose those with the lowest resistance. These include all metals.

There are special coefficients that are used to determine the resistance of a grounding loop operated under different conditions. Eg:

in private housing construction, where networks of 220 and 380 volts (6 and 10 kV) are used, it is necessary to install a circuit with a resistance of 30 Ohms.

the installed gas pipeline system entering the house must be grounded with a 10 ohm circuit.
lightning protection must have a resistance of no more than 10 ohms.
Telecommunications equipment is grounded using a 2 or 4 ohm loop.
Substations from 10 kV to 110 kV – 0.5 Ohm.

That is, it turns out that the greater the current power inside the equipment or devices, the lower the resistance should be.

Principle of operation

Electrical safety standards require that protective grounding and lightning protection be installed in any home. Grounding installation in private houses is much simpler than in apartment buildings. Read the article on how to make it correctly and measure resistance.

If a breakdown occurs in the case, due to grounding, most of the current will flow through the grounding part. Together with the conductors, the ground electrode forms a grounding device. There are several types of grounding:

lightning protection, consisting of a lightning rod, a lightning rod and a ground electrode in the ground;
protective, preventing electric shock to people if a breakdown occurs from a phase wire to the body of the electrical installation;
workers, for normal operation of electrical installations in normal and emergency conditions.

Grounding electrodes can also be divided into natural and artificial. Natural - these are metal structures of the building, pipelines. Artificial - specially mounted structures (steel strips, angle steel and others).

There is a unified classification of grounding systems for electrical installations up to 1 kV, accepted almost throughout the world. According to it, in equipment with voltages up to 1 kV, three grounding systems are used: TN, TT, IT.

According to the rules for operating electrical installations, grounding and grounding must be present in two cases:

if the alternating voltage is more than 42 V, and the direct voltage is more than 110 V, in outdoor and especially dangerous electrical devices;
if in any electrical installations the alternating voltage is higher than 380 V, direct voltage is more than 440 V.

The installation of grounding in private houses is regulated by the following regulatory documents, and before putting the building into operation it will be necessary to measure the resistance of grounding devices:

Video “Protective grounding in a private house”

Internal protective grounding consists of separate conductors coming from powerful power plants. They are connected into a bus inside the shield. The copper cable connects the busbar and the plate with a bolted connection.

First you need to decide on grounding schemes. Currently, two types of schemes are used:

linear, where the pins are buried sequentially in one line. The scheme is not particularly reliable, since if one connection fails, the entire system will stop working;
closed, triangular. A closed circuit is more reliable, since if the jumper between the pins is damaged, the circuit will continue to work.

Here are step-by-step instructions on how to install protective grounding. Before installation, you will need a set of the following tools and equipment: bayonet shovel, welding machine, grinder, hammer drill, wrenches and sledgehammer. From the materials you need to prepare:

copper wire no less than 6 mm square. in cross section;
a stainless steel corner of at least 2 meters or a rectangular profile with a cross-section of 150 mm2;
stainless steel strip from the porch to the system, 40*4 mm;
M10 or M8 bolts;
three metal strips (width 4 cm, thickness 0.5 cm, length 120 cm).

Expert opinion

Viktor Pavlovich Strebizh, lighting and electrical expert

Any questions ask me, I will help!

Compliance with the requirements of the PUE for the ratio of conductivity cross-section is a generally obligatory aspect of the selection of any device as a grounding element. If there is something you don’t understand, write to me!

What is a ground electrode and what can be used as a ground electrode?

What is a ground electrode?

GROUNDING LEADER - a conductive part (or a set of interconnected conductive parts) that is in contact with the ground directly or through an intermediate conductive medium.

What can a grounding conductor be made from?

1.7.109. The following can be used as natural ground electrodes: 1) metal and reinforced concrete structures of buildings and structures in contact with the ground, including reinforced concrete foundations of buildings and structures that have protective waterproofing coatings in non-aggressive, slightly aggressive and moderately aggressive environments; 2) metal water pipes laid in the ground; 3) casing pipes of boreholes; 4) metal sheet piles of hydraulic structures, water conduits, embedded parts of valves, etc.; 5) rail tracks of main non-electrified railways and access roads if there is a deliberate arrangement of jumpers between the rails; 6) other metal structures and structures located in the ground; 7) 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 cable sheaths are not allowed to be used as grounding conductors.

What cannot be used as a grounding conductor?

1.7.110. It is not allowed to use pipelines of flammable liquids, flammable or explosive gases and mixtures, and sewerage and central heating pipelines as grounding conductors. 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. Reinforced concrete structures of buildings and structures with prestressed reinforcement should not be used as grounding conductors, however, this restriction does not apply to overhead line supports and outdoor switchgear support structures. The possibility of using natural grounding conductors based on the density of currents flowing through them, the need to weld reinforcing bars of reinforced concrete foundations and structures, welding anchor bolts of steel columns to reinforcing bars of reinforced concrete foundations, as well as the possibility of using foundations in highly aggressive environments must be determined by calculation.

Requirements for artificial grounding conductors?

1.7.111. Artificial grounding conductors can be made of black or galvanized steel or copper. Artificial grounding conductors should not be painted. 1.7.112. The cross-section of horizontal grounding conductors for electrical installations with voltages above 1 kV should be selected according to the condition of thermal resistance at a permissible heating temperature of 400 °C (short-term heating corresponding to the duration of the protection and tripping of the circuit breaker). In case of danger of corrosion of grounding devices, one of the following measures should be taken: increase the cross-sections of grounding conductors and grounding conductors, taking into account their estimated service life; use galvanized or copper grounding conductors and grounding conductors. In this case, one should take into account the possible increase in the resistance of grounding devices due to corrosion. Trenches for horizontal grounding conductors must be filled with homogeneous soil that does not contain crushed stone and construction waste. Grounding electrodes should not be located (used) in places where the ground is dried out by the heat of pipelines, etc.

Deaf neutral immersion

Grounding systems are divided into two large groups: with a solidly grounded neutral and with an isolated one. In the first type of circuit, the neutral conductor (denoted N) is always grounded and can be independent of the protective PE conductor, or can be connected to it to form a PEN conductor.

Application of the TN-C system

Application of the TN-S system

The TN-S system is more advanced, has a high degree of electrical safety, since it has a separate grounded conductor, but its cost is unreasonably high. With three-phase power, you have to lay five wires from the source - three phases, a neutral and a protective conductor PE.

CT grounding type

Grounding electrodes. 1.7.109. They can be used as natural grounding agents.

According to regulatory documentation, this indicator is considered the main one for determining the quality of the grounding device. Resistance regulates the reliability of production of the main functions of grounding elements.

Expert opinion

Viktor Pavlovich Strebizh, lighting and electrical expert

Any questions ask me, I will help!

The internal grounding loop is a closed circuit of conductors connecting the metal elements of electrical equipment with the external grounding loop located inside the building;. If there is something you don’t understand, write to me!

What acts as an artificial grounding conductor

The grounding element is made in the form of a conductor (electrode) of a certain material, which is placed in the ground. In some cases, several similar grounding conductors are installed.

Determining the situation when it is necessary to install a group of artificial rods is realized through special calculations. The result of the calculation justifies the choice of electrode configuration in relation to its resistance - the main indicator that determines the quality of grounding.

An artificial ground electrode is made from the following materials:

Copper-plated steel. The connection between copper and steel has good adhesion. The rods are durable and have excellent contact with any materials. Due to its chemical properties, the alloy has excellent electrical conductivity. The electrochemical activity of copper and steel is insignificant; normal operation of ground electrodes made of such metal can reach more than a hundred years.
Cink Steel. Advantages: corrosion resistance of the material, low resistance, electrodes are resistant to acidic environments.
Black metals. Disadvantage: rapid destruction in aggressive soil (corrosion and rust form). The high strength of the material increases the resistance to current spreading, which is extremely dangerous for humans.

In addition to the material, artificial ground electrodes differ in shape and location in the soil (deep vertical and extended horizontal type).

Description of protection

Precast concrete foundations have good structural characteristics in both structural strength and durability. It is not prohibited to connect a grounding conductor to such a foundation.

The main thing is to make the correct connection of structural elements. By fastening the reinforcement of adjacent blocks together, you can verify the reliability of the structure, and then begin production of the grounding device.

If it is not possible to make such a connection, it is better to resort to the use of an artificial ground electrode. It is necessary to make connections of this type of structure taking into account the profile standardization of the production of such work.

Electrode placement

The parts included in the general grounding structure can be located vertically or horizontally. In the first installation method, the electrodes are buried 70 cm into the ground. However, their length should not exceed 5 m, and their diameter should be in the range of 10-16 mm.

The horizontal laying method involves deepening the grounding bars by 50 cm (in the case of arable land by 1 m). Horizontally located steel rods with a diameter of more than 1 cm (or steel strips with a thickness of more than 4 mm) are used to connect vertically installed elements, the joints between them are fixed by welding. This method shows its effectiveness only if there is sufficient electrical conductivity of the top layer of soil.

Electrical installation rules require grounding for electrical equipment for domestic and industrial purposes. There are no clear requirements regarding how the electrodes should be located in the ground. In each specific case this is determined individually.

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Electrical safety created with the help of artificial grounding conductors is realized by reducing the potential difference and removing stray current. Leakage current occurs due to the interaction of the grounding element and the phase cable. At the same time, uninterrupted and efficient functioning of electrical equipment is ensured.