Modular grounding- this is a project created specifically for the installation of grounding conductors at residential facilities, for example, such as private country houses, country houses, as well as for industrial and administrative facilities.
Practice of installing a modular grounding loop.
A modular ground electrode is a prefabricated structure consisting of steel pins specially treated with copper, each 1.5 meters long. These pins are combined into a single grounding circuit for grounding the object.
The length of the prefabricated grounding rod can reach a depth of about 30 - 40 meters. The 1.5 meter grounding pins have threads at the ends, through which and connecting couplings between them, it becomes possible, as the assembled grounding pin moves deeper, to extend it with the next pin, etc.
Installation of a vertical grounding pin in depth is done as follows. The first pin is equipped with a steel tip at the bottom, and a mounting sleeve with an attachment for a vibrating hammer is screwed onto its upper part. A hammer or hammer drill is used to strike the nozzle, and a special clamp is used to hold the pin in a vertical position.
When the first pin enters the ground to a length of approximately 1.3 - 1.4 meters, the mounting coupling with the attachment for the vibrating hammer is removed, and instead of them, the second pin is screwed through the coupling. A special clamp to hold the pin in a vertical position moves up the newly mounted structure, and its top is again equipped with a mounting sleeve and a hammer attachment, and the process of driving in the grounding pin continues.
The circuit of the modular grounding pin is shown in the diagram below, where:
1. Attachment for a hammer or vibratory hammer.
2. Mounting coupling.
3. Clamp to hold the ground rod in a vertical position.
4. Coupling coupling.
5. Ground rod.
6. Steel tip.
Several such modular grounding conductors are installed for the grounding loop (according to the design), and then they are connected to each other, by means of a copper strip or wire using clamps, into a single grounding loop. When installing clamps, these places are pre-treated with conductive paste, and after complete installation of the entire grounding loop, it is subjected to anti-corrosion painting.
Measuring the resistance of a mounted vertical pin is possible at the installation stage of each newly screwed 1.5 meter pin, and the service life of such a modular grounding loop is approximately 30 years.
Advantages of modular grounding.
We want to talk in this article about how to properly equip grounding in a private home. In it we will dwell in detail on materials, installation and grounding devices. You will learn about what modular pin grounding is, the materials needed to install it, and how to control the mounted grounding.
Electricity and safety precautions when using it
When using electricity, there is a potential for hazardous situations to occur. To avoid this there are different means. The most important and reliable means is a device called a protective power cut. Another protective device that helps to avoid dangerous situations is the creation of a grounding loop and connecting to it all the electrical equipment that is in the house. A point is created to supply electricity to a private home. It is indicated in the permitting technical conditions and becomes the electricity supply organization. Four conductors are suitable for each connection point (to the distribution board), three are phases (L1, L2, L3), and the fourth conductor, created specifically at the substation, is the grounding conductor (N). It is also called "earth", although correct name sounds like “neutral”. There is no voltage on it, and it serves as a pair for the phase wire. It should be noted that the number of wires and cores in the cable depends on the technical characteristics that the home owner specified when connecting. The declared voltage can be of two types - 220V or 380V.
- When applying for 220V, two cables or two wires are supplied to the house.
- If you need 380V, then four cores in the cable or four wires are supplied.
To connect the lighting, only one phase and one neutral are enough. According to the new rules (PUE), three wires (cable, cord) must be suitable for each electrical appliance that is designed for 220V:
- live phase wire (L);
- neutral wire (N);
- protective neutral wire (PE), its other name is “protective grounding”.
Regardless of the wiring system that runs in the house (it can be three-wire or five-wire) starting from distribution panel, only three groups of wires are laid around the house:
- lighting - two wires - phase and neutral (L and N), 1.5 mm2 - cross-section.
- socket - three wires (L, N, PE) wire cross-section not less than 2.5 mm2.
Electrical equipment (power) - three cables (L, N, PE), the cross-section is calculated relative to the power of the equipment. But we should not forget that the protective (PE) and neutral (N) conductors cannot be larger than the phase conductor; their cross-section must be smaller or at least equal to wire L. But with all this, the “neutral” and protective conductor cannot be connected in shield under one contact clamp. With proper design, the power panel looks like this: it has two phase wires, one “ground” and a ground bus (PE). A ground loop is connected to the bus.
According to international standards, both the phase wire and the “neutral” are considered to be power wires. This means that certain requirements must be met: It is necessary to insulate all wires from the housing in the design of the device.
IN general scheme“neutral” and phase are power conductors, which means that the neutral wire cannot be used instead of the PE protective wire. This is caused by the fact that sometimes a “bias voltage” appears at the “neutral”. This phenomenon also occurs in a working system. Sometimes it can be 50V, which automatically turns it from a protective wire into a dangerous one!
DIY grounding
The potential of the protective conductor PE with the help of a ground loop will always be equal to the potential of the soil (earth). This means that the body of the device connected to the circuit will also be equal to this potential. This is why it is very important to keep the ground circuit resistance under control. Ideally, it should not be more than 4 ohms. According to the diagram, the grounding conductor consists of a grounding conductor and a grounding conductor. 
The metal conductor that is in contact with the ground is called a ground electrode. And the metal conductor that connects the PE bus from the electrical panel to the grounding conductor is called the grounding conductor.
For the grounding device, a circuit is created that includes: a power distribution panel (with a PE bus), a ground electrode, a ground wire and an electrical appliance.
According to the PUE, namely clause 1.7.70, they can be used as a grounding conductor various designs that are suitable for such purposes. In addition, natural grounding agents are used. Namely:
- water and other metal pipelines in which the pipes are connected to each other by electric and gas welding. The exceptions are pipes with flammable liquids, explosive and hot gases and mixtures, central heating and sewage pipes;
- metal and reinforced concrete frames of buildings that are in contact with the ground;
- well pipes.
When using such natural grounding conductors, it is necessary to remove a branch - lay a grounding wire from such a structure to the PE bus of the electrical panel. The bend should be connected to the structure using bolts or welding. To do this, first a steel plate is welded to the structure and only then a wire (made of copper) is attached.
If a natural grounding conductor is used as a grounding conductor, the service life of the grounding conductor is reduced due to current leakage through the structure. It follows from this that it is better to use a separate artificial ground loop as a grounding conductor.
In addition, if the structure of the house is wooden and there are no natural grounding electrodes nearby, then artificial ones should be used.
For this type of grounding conductors, round steel blanks are used. The diameter of the workpiece must be greater than 16 mm. You can use a steel corner for these purposes (with parameters 50x50x5 mm). The length of the workpieces should correspond to 3.0 - 3.5 meters. The workpiece should be driven into the ground (vertically), leaving no more than 10 centimeters above the ground. A trench (0.7 m deep) is laid between the grounding conductors. Wires are laid in it that connect the grounding conductor blanks to each other.
The cross-section of the connecting wires is at least 16 mm; the structure is connected by welding.
This circuit is connected to the PE bus with a wire (2.5 mm2). The thickness of the ground wire cannot exceed the thickness of the phase wire. The grounding wire can be connected to the PE bus using a bolt or welding (any type). This is necessary to create not only the grounding itself, but also for additional contact area. 
If there is a utility room near the house that contains power equipment (lathes, electrical appliances with increased energy consumption), then power supply must be connected to it (in the form of two or four cables). Then this room is subject to additional grounding. An internal grounding loop must be created around the perimeter of the room itself. It is performed using a steel strip (the cross-section of which is 24 mm). The strip should be at a height of 0.8 m from the floor level. The housing of electrical appliances is connected to the circuit using a steel strip (size 20x5 mm) or copper wire (2.5 mm). The internal circuit is connected to the ground electrode. But there must be more than two connection points.
Example of a grounding device
Before installing a grounding loop, a calculation must be made and a project must be created. All subsequent work must be carried out in accordance with this project. After all, constructing a circuit is quite a difficult task. To do this you will have to carry out earthworks, make calculations of the electrical resistance of the earth in a given area, carry out welding and installation work. To carry out high-quality grounding work, specialists are usually invited, but this type of work can be done independently.
To save materials and effort, the circuit should be created near the distribution panel. To build a contour and then attach it to the shield, you will need the following materials:
- Steel rods,
- with a diameter of 16 mm (three pieces),
- steel corners,
- size 50x50x5 mm (three pieces).
They will provide the required resistance, regardless of the resistivity value of the land plot.
About 9 m of steel strip, 4x40 mm in size.
A steel strip that will run from the circuit to the distribution panel (meterage depending on the distance).
First you need to dig a trench (depth 0.7 m and width 0.5 m). The trench should run from the house to the location of the circuit. At the contour site, the trench takes the shape equilateral triangle with a side of 3 meters. At each vertex of the triangle, drill holes to a depth of 3 m. Steel rods must be driven into these holes. If the ground is soft, then the rods are driven in with a sledgehammer, and if it is hard, then the rods should first be sharpened on one side and then driven into the ground using a weight. A steel strip should be welded to the corners, located at a height of 0.01 m from the bottom of the trench. This is what a grounding source looks like.
A steel strip is laid from the resulting contour to the house. One side of this strip should be attached to the circuit, and the other to the PE bus located in the power distribution panel.
Then the entire structure is covered with soil. The soil should be free of debris and rubble. To reduce the circuit resistance, it can be additionally connected to metal fence, metal poles or metal supports. The welding areas (which are overlapped) must be coated with bitumen varnish to avoid corrosion.
If from overhead line If three-phase or single-phase electricity is supplied to the house, then additional grounding of the “neutral” (neutral conductor) at the input to the power panel should be performed. This device must also be connected to the ground loop.
Modular pin system
The equipment market is widely advertised and sells well new system grounding, which is called modular pin. The high-tech new system is installed regardless of technical specifications, limited area for installing the circuit. 
So what are the advantages of this grounding system? How is it installed and what is needed for this? Below you will learn everything about this grounding system.
To accommodate the modular pin system you will need one square meter of area. To install it you will need a hammer drill. During installation, there is no need to drill holes under the workpieces in order to achieve the required resistance value. All work is carried out using a hammer drill (it works like a drill). The elements of this system are connected using special couplings. If missing additional area, to install the circuit, and the ground is quite soft near the house, then a modular pin ground circuit is installed. Deep installation allows the ground electrode to be recessed 40 meters deep into the ground. This provides required parameters required grounding and soil resistance. If the hardness of the soil does not allow deep grounding, then the installation of the circuit described above (regular circuit) is used.
Two qualified personnel are required to install the pin system. During installation, a mandatory measurement of soil resistance is carried out throughout the advance into the soil. This is necessary to control grounding parameters. The grounding modules of this system are connected using special clamps, which after installation are insulated with tape (waterproofing) to avoid corrosion of the metal and connections. 
The pin grounding system is much more expensive than the classical system. But we should not forget that its service life is many times longer than that of a conventional circuit, which is made using steel corners and metal strips.
When the grounding system is completely installed, the loop resistance should be measured. This is necessary to obtain a passport, which is issued in accordance with the standards specified in PTEEP and PUE. A passport form can be obtained from these organizations.
To determine which is more profitable to install, we will conduct comparative characteristics prices of materials for both systems. The installation and materials cost for the pin system is approximately $500 (materials) and $120 (installation). Which ultimately adds up to $620. With the classic system, installation will cost the same $120, and materials will cost $100, which, in general, will be $220. Although the classic one is cheaper, it only takes half an hour to install the pin system. In addition, it requires much less space and energy consumption. 
Instruments used to measure grounding resistance
After carrying out all the work on installing the circuit, it is necessary to check the quality of the work and the quality of the grounding source. It is required to take readings of all resistances and compare the results with the standards of PTEEP and PUE. This is all done using special devices.
First carried out visual inspection all parts of the grounding system. To do this, use a hammer to tap all welding and fastening points. You should make sure that everything is connected securely and that there are no cracks at the joints, and that the connections with bolts are securely twisted. The results of the check are recorded on a special registration sheet, which is in the passport. 
According to the rules that apply to electrical installations (PUE) up to 1000V and have a solid grounding of the neutral conductor, the resistance of the grounding device cannot exceed 4 ohms. This value is obtained by adding the resistance of the grounding conductors relative to the ground and the resistance of the grounding wire.
These values can be measured using instruments - ohmmeters: M416, Anch 3, EKO 200, KTI 10, EKZ 01, IS 10, MRU 101, MRU 100 and many other devices for measuring resistance. All these devices are included in the only register of countries - Russia, Kazakhstan, Ukraine, Uzbekistan, Belarus.
Conclusion. In this article, two types of grounding systems for a private house were considered. Now you can perform grounding own home on one's own. But if you have questions, please contact qualified specialists for help. After all, the safety of your home depends on properly installed grounding.
Grounding device in the cottage
The grounding device in the cottage is performed in many ways. One of the main disadvantages of many grounding devices is the instability of grounding properties over time. In addition to seasonal changes in grounding properties, corrosion of grounding conductors constantly occurs.
Grounding to a depth below the level groundwater and, naturally, deeper than the freezing depth for a given area. The most common method of solving this problem is driving metal rods approximately 2...3 m long into the ground, often from a special trench 0.3...0.8 m deep. The upper ends of the rods are connected into a contour measuring no more than 16x16 m with a metal strip using welding and bury themselves. Naturally, conclusions are drawn outward from the same strip. And they fight conductor corrosion by making these conductors from of stainless steel.
It is very convenient and economical to make a ground loop at the stage of foundation construction or drainage system, naturally taking into account everything said above regarding sizes and depths. As a rule, it is convenient to place the contour a little deeper than the location of the lower parts of the foundation or drainage system pipes and lay it in a groove (as wide as a shovel and about 0.3 m deep) dug around the perimeter of the bottom of the pit or along the bottom of the drainage system trench. To reduce the grounding resistance, it is recommended to fill the groove with crushed stone, having previously laid a metal conductor at the bottom. Hammering metal rods into the bottom of the groove and welding them to the contour is also not prohibited, but with a sufficient depth of the contour, the number of rods can be small. Do not forget that the ground loop must be closed and cover a large area. It is desirable that the outline be close to a square in plan. The ideal material for grounding device conductors is stainless steel. This is because a stainless steel grounding device, unlike other materials, practically does not change its properties over time.
All connections must be made by welding or stainless riveting. The cross-section of a stainless or galvanized steel conductor for the grounding device should not be less than 75 mm.
There are special rods and bars made of stainless or galvanized steel measuring 30x3.5 mm on sale.
Instead of rods you can use stainless steel pipes with a suitable cross-section for metal. Often, for tires, stainless steel wire with a diameter of 6 mm is used, laid in three or four times and welded every meter, or a stainless steel strip of no less cross-section (you can simply cut a stainless steel sheet 3.5...4 mm thick on a metal base into strips 30 mm wide, which then welded at the ends). Sometimes the horizontal parts of the circuit are made from long pieces of stainless steel scrap metal, welded together, etc. Do not forget to remove vertical bends of the same cross-section from the circuit to in the right places for connection to the main grounding bus (GZSH) and the lightning protection system.
The figure shows a sectional view of the design of the grounding loop in the foundation pit.
If the splitting of the combined neutral wire is carried out on a support, then a re-grounding line must be drawn from the grounding loop to the support. The re-grounding line is made of the same material and the same cross-section as the circuit itself. This line is laid directly in the ground (recommended depth 1 m, but not less than 0.3 m) and from the side of the cottage it is connected to the ground loop in the street cabinet on the main building.
(Since the grounding device is also used for the lightning protection system, it is necessary to avoid laying the route of this line under pedestrian paths and places where people may often be!)
From the opposite end, the re-grounding line goes directly to the support and rises along it to the point of connection to the neutral wire. All connections on the line are made by welding or stainless riveting. The grounding line can be secured to the support using clamps or brackets made of stainless tape or wire.
Installation on the line and support cannot be done independently. It can only be done on a project basis and the work must only be carried out by local service organization VL.
The story is about how I did grounding.
Having studied the issue of grounding devices, I decided to spend a little more money and make a fashionable pin grounding. Close to home. No large-scale earthworks for you. No welding. Swinging a sledgehammer. In general, a blunder and nothing more.
Previously, on occasion, for various needs, a 25 J hammer drill was purchased, which was perfectly suited for the event of installing pin grounding. Then I began to choose the grounding itself. I didn't want to buy something too expensive. I decided to outwit the “toad” a little. I found a grounding from tselectric. A set of 4 pins seems to be reasonably priced relative to well-known competitors. But as they say, “wouldn’t go after what’s cheap.” All the pins look quite decent, copper-plated. Starting attachment for the first pin, coupling. Sledgehammer attachment. And since the hammer drill is available, I of course ordered a guide for the vibratory hammer (okay, 2 pieces) and the insert itself for the hammer drill.
And a clamp for connecting tape or wire.I've seen enough movies to see how everyone is having fun driving in pin grounding. Day X has arrived. I prepared everything and unpacked it. I dug a hole about 50 cm deep. I assembled the first pin and let’s drive it into the ground with a hammer drill. It cannot be said that it was effortless, but it went into the ground quite easily. However, I discovered that the guide for the hammer drill was tightly welded to the insert in the hammer drill. The whole thing heats up when hammering, not sour. Anyway. I removed the hammer drill from the attachment. I unscrewed the guide with a gas wrench. Tightened the second pin. Continued the perforation exercises. Here I noticed that when driving, the whole thing unwinds, and chips fall out of the coupling. Like the thread works. Although I was constantly twisting and tightening, it was clearly not great. I drove the second pin. Screwed on the third one. Started hitting him.
The process became more complicated. Aaaand, when the second coupling went into the ground 30 cm from the bottom of the hole, when I tightened the coupling again, the 3rd pin ended up in my hands. Unpleasant feeling. Having pulled it out, I discovered that there were practically no threads on the other side of the coupling.
I began to feverishly think about what to do. What should I do. First, I decided to dig up what had gone into the ground. And I decided, in order not to lose the second part of the 6m structure, to ground 2 pins of 3 m each. 3 meters are already in the ground. I really didn’t want to dig a trench, but I had to. He retreated 1.5 m and decided to hit the second part of the pin with a sledgehammer. Scored. But even when driving with a sledgehammer, chips fell out of the coupling, but not so actively. I hammered most of it in with a sledgehammer and dug it deeper into the hole with a hammer drill. The first conclusion regarding this grounding manufacturer. Weak couplings. Hammer only with a sledgehammer. And it’s good that I ordered a pair of guides for the hammer drill. The first one, which was welded, had to be cut down with a grinder, because it was not possible to knock it off the nozzle. Parts of the thread from the coupling were welded into its thread. It was no longer possible to use it. But the funny thing is that even after sharpening the tip for the hammer drill, so that it dangles a little more freely on the nozzle, even with little use, in the end they catch up with the hole. They were welded to each other again.The photo shows the remains of a sawn nozzle. The nozzle and guide became a single whole, but I was thinking about buying the same set for a second house. Apparently it's not fate.
But somehow it was necessary to get out of this situation.
As a result, I used a hoe to get to the end of the pin that had fallen off the coupling. A pin appeared at a depth of 80 cm. I washed it with water. I took a photo and enlarged it. He noted that the carving was alive. And I still had one more whole coupling left. Moreover, on the farm there was a 14 mm wire rod with a thread cut on both sides M16x2, like the coupling and pin from the kit. And even with nuts. A miracle, and only in this situation. Although if it hadn’t been there, I would have gone to buy such a threaded rod. Fortunately, they are sold in the nearest city. He screwed on the coupling, tightened it with a nut and began to tighten it with a breath on the protruding rod. And it dragged on. Hallelujah.
This is what happened.Now we need to think about how to connect this to the second pin. We dig a trench.
We buy a couple of meters of 4x40 tape. But there is no second fastener for the tape. There is no desire to cook at all; for this you need to carry out completely different excavation. But my wife did not allow us to turn everything around the house around because of the tree roots. Fortunately, this small trench passed them by.
I found an original solution.
I assembled an improvised fastener from galvanized iron using a grinder and a drill.
Under " grounding"is understood electrical connection equipment, devices to the grounding device, which in turn is connected to the ground (earth). The purpose of grounding is to equalize the potential of equipment, circuits and ground potential. Grounding is required for use at all power facilities to ensure the safety of workers and equipment from short circuit currents. When a breakdown occurs, the short-circuit current flows through the grounding device circuit to the ground. The current passage time is limited by the action of relay protection and automation. This ensures the safety of equipment, as well as the safety of workers in terms of damage electric shock.
To protect electronic equipment from electrostatic potentials and limit the voltage of the equipment case for the safety of operating personnel, the resistance of an ideal grounding circuit should tend to zero. However, in practice this is impossible to achieve. Considering this circumstance, modern safety standards specify rather low permissible values of resistance of grounding circuits.
Grounding device resistance
The total resistance of the grounding device is composed of:
- The resistance of the metal of the electrode and the resistance at the point of contact between the grounding conductor and the grounding electrode.
- Resistance in the area of contact between the electrode and the ground.
- Ground resistance in relation to flowing currents.
In Fig. Figure 1 shows a diagram of the placement of a grounding electrode (pin) in the ground.
As a rule, the grounding pin is made of a metal that conducts electric current (steel or copper) and is marked with the appropriate terminal. Therefore, for practical calculations, we can neglect the resistance value of the grounding pin and the point of contact with the conductor. Based on the results of the studies, it was found that if the installation technology of the grounding device is observed (close contact of the electrode with the ground and the absence of foreign impurities in the form of paint, oil, etc. on the surface of the electrode), due to its small value, it is possible to ignore the resistance at the point of contact of the grounding electrode with earth.
Soil surface resistance is the only component of the grounding device impedance that is calculated during the design and installation of grounding devices. In practice, it is believed that the grounding electrode is located among identical layers of soil, arranged in the form of concentric surfaces. The closest layer has the smallest radius and therefore the minimum surface area and the greatest resistance.
As you move away from the ground electrode, each subsequent layer increases its surface area and decreases its resistance. At some distance from the electrode, the resistance of the soil layers becomes so small that its value is not taken into account for calculations. The area of soil beyond which the resistance is negligible is called the area of effective resistance. The size of this area is directly dependent on the depth of immersion of the grounding electrode into the soil.
The theoretical value of soil resistance is calculated using the general formula:
where ρ is the value of soil resistivity, Ohm*cm.
L – thickness of the soil layer, cm.
A – area of concentric soil surface, cm2.
This formula clearly explains why the resistance of each soil layer decreases with distance from the grounding electrode. When calculating soil resistance, its resistivity is taken as a constant value, but in practice the value of resistivity varies within certain limits and depends on specific conditions. Formulas for finding grounding resistance at large number grounding electrodes have complex look and allow you to find only an approximate value.
Most often, the grounding resistance of a pin is determined using the classic formula:
where ρ is the average value of soil resistivity, Ohm*cm.
R – electrode grounding resistance, Ohm.
L – depth of the grounding electrode, cm.
r – radius of the grounding electrode, cm.
Influence of the dimensions of the grounding electrode and the depth of its grounding on the value of grounding resistance
The transverse dimensions of the grounding electrode have little effect on the grounding resistance. As the diameter of the grounding pin increases, a slight decrease in grounding resistance is observed. For example, if the diameter of the electrode is doubled (Fig. 2), then the grounding resistance will decrease by less than ten percent.
Rice. 2. Dependence of the resistance of the grounding pin on the diameter of its cross-section, measured in inches
As the depth of placement of the grounding electrode increases, the grounding resistance decreases. It has been theoretically proven that doubling the depth can reduce drag by as much as 40%. In accordance with NEC standard (1987, 250-83-3) to ensure reliable contact The pin should be immersed with the ground to a depth of at least 2.4 meters (Fig. 3). In many cases, a three meter grounded pin will fully satisfy current NEC standards.
NEC Standards (1987, 250-83-2) require a minimum diameter of 5/8" (1.58 cm) for a steel grounding electrode and 1/2" (1.27 cm) for a copper coated steel or copper electrode. cm).
In practice, the following transverse dimensions of the grounding pin are used with a total length of 3 meters:
- Regular primer – 1/2" (1.27 cm).
- Wet soil – 5/8" (1.58 cm).
- Hard ground – 3/4" (1.90 cm).
- For a pin length of more than 3 meters – 3/4 "" (1.91 cm).
Rice. 3. Dependence of the resistance of the grounding device on the grounding depth (vertically - the value of the electrode resistance (Ohm), horizontally - the grounding depth in feet)
Influence of soil resistivity on the value of electrode grounding resistance
The above formula shows that the value of grounding resistance depends on the depth and surface area of the grounding electrode, as well as on the value of soil resistivity. The latter value is the main factor determining the grounding resistance and the depth of electrode grounding required to ensure minimum resistance. Soil resistivity depends on the time of year and point globe. The presence of electrolytes in the soil in the form of aqueous solutions of salts and electrically conductive mineral substances greatly affects the soil resistance. In dry soil that does not contain soluble salts, the resistance will be quite high (Fig. 4).
Rice. 4. Dependence of soil resistivity (minimum, maximum and average) on the type of soil
Factors influencing soil resistivity
With extremely low moisture content (close to zero), sandy loam and ordinary soil have a resistivity of over 109 Ohm*cm, which allows such soils to be classified as insulators. An increase in soil moisture to 20 ... 30% contributes to a sharp decrease in resistivity (Fig. 5).
Rice. 5. Dependence of soil resistivity on moisture content
The resistivity of the soil depends not only on the moisture content, but also on its temperature. In Fig. Figure 6 shows the change in the resistivity of sandy loam with a moisture content of 12.5% in the temperature range of +20 °C to –15 °C. The resistivity of the soil when the temperature drops to – 15 °C increases to 330,000 Ohm*cm.
Rice. 6. Dependence of soil resistivity on its temperature
In Fig. Figure 7 shows changes in soil resistivity depending on the time of year. At significant depths from the surface of the earth, the temperature and humidity of the soil are quite stable and less dependent on the time of year. Therefore, a grounding system in which the pin is located at a greater depth will be more effective at any time of the year. Excellent results are achieved when the ground electrode reaches the groundwater level.
Rice. 7. Change in grounding resistance during the year.
Used as a grounding device water pipe(¾""), located in rocky ground. Curve 1 (Curve 1) shows the change in soil resistance at a depth of 0.9 meters, curve 2 (Curve 2) - at a depth of 3 meters.
In some cases, an extremely high value of soil resistivity is observed, which requires the creation of complex and expensive protective grounding systems. IN in this case you need to install a ground pin small sizes, and to reduce the grounding resistance, periodically add soluble salts to the surrounding soil. In Fig. Figure 8 shows a significant decrease in soil resistance (sandy loam) with increasing concentration of salts contained.
Rice. 8. Relationship between soil resistance and salt content (sandy loam with humidity 15% and temperature +17 °C)
In Fig. Figure 9 shows the relationship between the resistivity of the soil, which is saturated with a salt solution, and its temperature. When using a grounding device in such soils, the grounding pin must be protected from the effects of chemical corrosion.
Rice. 9. The influence of the temperature of soil impregnated with salt on its resistivity (sandy loam - salt content 5%, water 20%)
Dependence of the resistance value of the grounding device on the depth of electrode grounding
To determine the required depth of the grounding electrode, a grounding nomogram will be useful (Fig. 10).
For example, to obtain a grounding value of 20 ohms in soil having a resistivity of 10,000 ohms*cm, it is necessary to use a metal pin with a diameter of 5/8 "" buried 6 meters.
Practical use of the nomogram:
- Set the required resistance of the grounded pin on the R scale.
- Mark the point of actual soil resistivity on the P scale.
- Draw a straight line to the K scale through the given points on the R and P scales.
- Mark a point at the intersection with the K scale.
- Select the required ground rod size using the DIA scale.
- Draw a straight line through the points on the K scale and on the DIA scale until it intersects the D scale.
- The intersection of this straight line with scale D will give the desired depth of the pin.
Rice. 10. Nomogram for calculating the grounding device
Measuring soil resistivity using the TERCA2 device
There is a large plot of land.
The task is to find a place with minimal resistance and estimate the depth of the soil layer with the lowest resistivity. Among various types soil found in this area, the minimum resistance will be in wet loam.
After a detailed examination of the site, the search area is narrowed to 20 m2. Based on the requirements for the grounding system, it is necessary to determine the soil resistance at a depth of 3 m (300 cm). The distance between the outermost ground pins will be equal to the depth for which the average resistivity is measured (in this case 300 cm).
To use the simplified Wenner formula
the grounding electrode should be at a depth of about 1/20 of the distance between the electrodes (15 cm).
The electrodes are installed according to a special diagram shown in Fig. eleven.
An example of connecting a grounding tester (Mod. 4500) is shown in Fig. 12.
Rice. 11. Installation of grounding electrodes along the grid
- Remove the jumper that closes terminals X and X V (C1 and P1) measuring instrument.
- Connect the tester to each of the 4 pins (Fig. 11).
Example.
The tester showed a resistance of R = 10 Ohms.
Distance between electrodes A = 300 cm.
Resistivity is determined by the formula ρ = 2 π *R*A
Substituting the initial data we get:
ρ = 2 π * 10 * 300 = 18,850 Ohm cm.
Rice. 12. Tester connection diagram
Touch voltage measurement
The most important reason for measuring touch voltage is to obtain a reliable assessment of the safety of substation personnel and the protection of equipment from exposure to high voltage currents. In some cases, the degree of electrical safety is assessed according to other criteria.
Grounding devices in the form of a separate pin or array of electrodes require periodic inspection and verification of resistance measurements, which are performed in the following cases:
- The grounding device is compact in size and can be temporarily disabled.
- When there is a threat of electrochemical corrosion of the grounding electrode caused by low soil resistivity and constant galvanic processes.
- If there is a low probability of a breakdown to ground close to the grounding device being tested.
As alternative way security definitions technological equipment substation uses touch voltage measurement. This method recommended in the following cases:
- If it is impossible to disconnect the grounding device to measure grounding resistance.
- In the event of a threat of ground faults near the grounding system being tested or in the vicinity of equipment connected to the grounding system being tested.
- When the circuit of the equipment in contact with the ground is comparable in area to the size of the grounding device to be tested.
It should be noted that measuring grounding resistance using the potential drop method or measuring touch voltage does not allow us to make a reliable conclusion about the ability of the grounding conductor to withstand significant currents when current leaks from the phase to the grounding conductor. For this purpose, a different method is required, in which a test current of significant magnitude is used. Touch voltage measurement is performed using a four-point ground tester.
In the process of measuring touch voltage, the device creates a small voltage in the ground, which simulates the voltage in the event of a fault in the electrical network near the point being tested. The tester shows the voltage value in volts per 1 A of current flowing in the ground circuit. To determine the highest touch voltage that can occur in an extreme case, multiply the resulting value by the maximum possible current.
For example, when testing a grounding system with the highest possible fault current of 3000 A, the tester returned a value of 0.200.
Therefore, the touch voltage will be
U = 3000 A * 0.200 = 600 V.
Measuring touch voltage is in many ways similar to the potential drop method: in each case it is necessary to install auxiliary ground electrodes in the ground. However, the distance between the electrodes will be different (Fig. 22).
Rice. 13. Grounding conductor diagram (general case for an electrical network industrial purposes)
Let's consider a typical case. Near the substation, an underground cable suffered insulation damage. Currents will flow through this place into the ground, which will go to the substation grounding system, where they will create a high potential difference. High leakage voltage can pose a significant threat to the health and life of substation personnel located in a dangerous area.
To measure the approximate value of the touch voltage that occurs in this case, you should perform a number of steps:
- Connect cable between metal fencing electrical substation and points P1 and C1 of a four-point grounding tester.
- Install a grounding electrode in the ground in the place where cable breakdown is most likely.
- Connect the electrode to input C2 of the tester.
- On the straight line between the first electrode and the point of connection to the fence, install an additional electrode in the ground. The recommended distance from the installation point of this electrode to the point of connection to the fence is one meter.
- Connect this electrode to point P2 of the tester.
- Turn on the tester, select the 10 mA range, record the device readings.
- To obtain the touch voltage value, multiply the tester readings by the maximum current value.
To obtain a voltage potential propagation map, it is necessary to install an electrode (of course, connected to the P2 terminal of the tester) in various places near the fence, located next to the faulty line.
Measuring grounding resistance with the "SA 6415" device using current clamps
Measuring ground resistance using current clamps is a new, very effective method that allows measurements to be carried out while the grounding system is turned on. This method also provides a unique opportunity to measure the total resistance of the grounding device, including determining the resistance of connections in current system grounding.
Operating principle of the device S.A. 6415
Rice. 14. Grounding conductor diagram (general case for an industrial power supply network)
Rice. 15. Operating principle of the grounding conductor
A classic grounding device for an industrial electrical network can be represented as schematic diagram(Fig. 23) or in the form of a simplified diagram of the operation of the grounding conductor (Fig. 24).
If voltage E is applied to one of the sections of the circuit with resistance RX using a transformer, then electric current I will flow through this circuit.
These quantities are related to each other by the relationship:
By measuring the current I at a known constant voltage E, we can determine the resistance RX.
In the diagrams shown (Fig. 23 and 24), a special transformer is used to generate current, connected to a voltage source through a power amplifier (frequency 1.6 kHz, constant amplitude). The resulting current is recorded by a synchronous detector in the resulting circuit, further amplified using a selective amplifier and, after conversion through an analog-to-digital device, displayed on the device display.
Typical examples of measuring ground resistance in real conditions
1. Measuring the grounding resistance of a transformer installed on a power line pole
Measurement procedure:
- Remove the protective cover from the grounding conductor.
- Provide the necessary space for the current clamp to freely reach the conductor or grounding pin.
- Clamps must be connected along the current path from the neutral or grounding wire to the grounding pin (pin system).
- Select current measurement “A” on the device.
- Grab the grounding conductor with a current clamp.
- Determine the current values in the conductor (the maximum permissible current is 30 A).
- If exceeded given value stop measuring resistance.
- Disconnect the device from this point and take measurements at other points.
- If the current value does not exceed 30 A, you should select the “?” mode.
- The display of the device will show the measurement result in Ohms.
The resulting value includes the total resistance of the grounding system, which includes: the contact resistance of the neutral wire with the ground pin, as well as the local resistance of all connections between the pin and the neutral.
Rice. 16. Measuring ground resistance on a power line pole
Rice. 17. Measuring the grounding of a transformer installed on a power line support (grounding in the form of a group of pins)
Rice. 18. Measuring the grounding of a transformer installed on a power line support (a metal pipe is used for grounding)
According to the diagram shown in Fig. 25, the end of the pole and a pin located in the ground are used for grounding. To correctly measure the total grounding resistance, current clamps should be connected at a point located above the junction of the grounding conductors laid from the grounding pin and the end of the pole.
The reason for the increased ground resistance value may be:
- Poor grounding of the pin.
- Disconnected ground conductor
- High resistance values in the area of conductor contacts or at the splice point of the ground wire.
- You should carefully inspect the current clamps and the connections at the end of the pin to ensure that there are no significant cracks at the joints.
2. Measurement of ground resistance on distribution box or on the electricity meter
The technique for measuring grounding on a distribution box and on an electric meter is similar to that discussed when measuring the grounding of a transformer. The grounding circuit can consist of a group of pins (Fig. 26) or a metal water pipe in contact with the ground can be used as a grounding conductor (Fig. 27). When measuring resistance grounding, both types of grounding can be used simultaneously. To do this, it is necessary to select the optimal point on the neutral in order to obtain the correct value of the total resistance of the grounding system.
3. Measurement of grounding resistance on a transformer installed on site
When carrying out grounding measurements at a transformer substation, you must remember:
- At this power facility there is always high voltage that is dangerous to human life
- The transformer enclosure must not be opened.
- All work may only be carried out by qualified specialists.
- When carrying out measurements, the requirements of safety and labor protection measures must be observed.
Rice. 19. Measuring the grounding value on a transformer located on a special site
Measurement procedure:
- Decide on the number of grounding pins.
- When the grounding pins are located inside the fence, measurements should be made according to the diagram shown in Fig. 28.
- When placing grounding pins outside the fence area, use the diagram shown in Fig. 29.
- If there is one grounding pin located inside the fence, you must connect to the grounding conductor at a point located after the contact of this conductor with the grounding pin.
- Using current clamps mod. 3730 and 3710 connected directly to the ground pin will, in most cases, provide top scores measurements.
- In many cases, several conductors are connected to the terminal on the pin, going to the neutral or into the fence.
- The clamp meter should be connected at the point where the only path for current to flow into the neutral conductor is.
If low resistance values are obtained, the measurement point should be moved as close as possible to the ground pin. In Fig. Figure 29 shows a grounding pin outside the barrier area. To ensure correct measurements, it is necessary to select the connection point for the current clamps in accordance with the diagram shown in Fig. 29. If there are several grounding pins inside the fence, you should determine their connection in order to select the optimal point for measurements.
Rice. 20. Choosing the correct ground measurement point
4. Transfer stands
When conducting grounding measurements on transmission racks, it should be remembered that there are many different configurations of grounding devices, which introduces certain difficulties when assessing grounding conductors. In Fig. Figure 30 shows a grounding diagram for a single rack on a concrete foundation with an external grounding conductor.
The connection point for the current clamps is selected above the connection point of the grounding elements, which can be designed in the form of a group of plates, pins, or be structural elements rack foundation.
Figure 21. Measuring the ground resistance of the transmission rack
In this article I will discuss a newer and more advanced grounding system - the modular pin system. You will become familiar with the conditions and methods of installing such a grounding center and the advantages of such a system. I also want to tell you how and with what help, without involving a special measuring laboratory, to monitor the resistance of the ground loop. I will tell you what to do if suddenly over time the resistance of the ground loop changes upward.
Modular pin grounding system
This system is formed by vertical steel rods and couplings. See Fig.1 and Fig.2. The rods, each 1.5 m long, are coated with a layer of copper. Couplings made of brass are designed to connect rods to each other.
Rice. 1 Ground Rod 58-11"UNC
- Rod length: 1500 mm.
- Rod diameter: 14.2 mm.
- Thread: 5/8”-11UNC on both sides, copper plated.
- Thread length: 30 mm.
- Weight, 1.85 kg.
Rice. 2 Connecting coupling MS-58-11
- Brass L-63 (production from bronze is allowed).
- Length 70mm.
- Diameter 22 mm.
- Internal thread: 5/8”-11UNC.
- Thread length 60 mm.
- Weight 0.114 kg.
The device includes a brass clamp required to connect the vertical and horizontal components of the ground loop. I will call the vertical component a steel rod, the horizontal component a steel strip or copper wire from the distribution panel to the grounding office. See Figure 3. The equipment includes two types of steel tips that are screwed onto a rod that is driven vertically into the ground. Each tip is used for a different type of soil: hard soil or regular soil. See Figure 4.
Rice. 3. Universal clamps MS-58-11
Rice. 4. Tip 58-11"UNC
- Tip length - 42 mm.
- The diameter of the steel tip is 20 mm.
- Thread: female 5/8”-11UNC.
- Thread length: 20 mm.
- Weight 0.045 kg.
The main equipment of the system is supplied with a landing pad (Fig. 5 and special attachment fig. 6. They are needed to apply and transmit the forces of the vibratory hammer.
Rice. 5. Landing pad 5/8”-11UNC
- Length 53 mm.
- Diameter 23.6 mm.
- External thread 5/8”-11UNC.
- Thread length 35 mm.
- Weight 0.110 kg.
Rice. 6. Impact nozzle NU
- Length 265 mm.
- The diameter of the main part is 18 mm.
- The diameter of the working part is 11.7 mm.
- The length of the working part is 14.5 mm.
The main equipment is supplied with anti-corrosion electrically conductive liquid paste for corrosion protection fig. 7 and protective tape fig. 8 for clamping connection of the vertical and horizontal components of the system.
Rice. 7. Anti-corrosion conductive lubricant
Electrically conductive graphite grease serves to create a permanent electrical circuit for the grounding vertical electrode. This is an all-season lubricating electrically conductive composition. Lubricant is applied to the threaded connections of all installation structures. It has good adhesion to the surface and its parameters do not change over time when the joint is heated with a current of 1.2 kA to a temperature of + 40C?. It protects against corrosion and maintains constant electrical resistance under operating conditions. When using lubricant, it is possible to reduce the joint resistance by 9-11%. When heated, the lubricant does not flow, and the resistance of the stacks is reduced by 55-60% due to the good filling of the uneven joints.
Rice. 8. Anti-corrosion tape
The tape is used to protect underground and aboveground pipes, rods, valves, fittings, and metal fittings from corrosion. It has good ductility even when exposed to temperatures. It is resistant to acids, alkalis, salts and microorganisms, does not allow water, water vapor and gases to pass through.
For ease of installation of this system, you must have a vibrating hammer (Fig. 9, and to control the resistance to spreading of the main grounding conductors - a resistance measuring device Fig. 10. I recommend using a vibratory hammer type BOSCH GSH 11 E Professional f. Bosch or MH 1202 E Makita f. Makita. As a device for measuring grounding resistance, I advise you to take a device type F4103-M1
Rice. 9. Vibrating hammer
Rice. 10 Ground resistance meter F4103-M1
Installation work
Installation of a resistance measuring device
We will install a device for measuring resistance next to the place where we are going to install the ground loop. The place for this we define a hole 200 x 200 x 200 mm, dug at a distance of 1.5 m from the exit of the horizontal component of the ground loop from the wall of the house. This can be a steel strip or copper wire. The measuring electrodes necessary for taking measurements are placed at a distance of 25 and 10 m along different sides from the device and drive them into the ground. Then we connect the electrodes to the F4103-M1 device.
See Figure 11 for the installation diagram of the measuring electrodes:
Fig. 11. Connection diagram for measuring electrodes
Installation of the first vertical modular pin
Let's start installing the grounding itself. We screw the tip onto one end of the rod. All threads on steel equipment, as the company guarantees to us, are applied after covering the rod and tips with copper. Before making the connection, treat the tip with anti-corrosion conductive paste. We screw a coupling onto the second end of the rod, which we also then fill with anti-corrosion conductive paste. We screw the landing head on top to apply the force of the vibratory hammer. We stick the mounted rod, tip down, as far as possible with manual effort into the prepared hole, into the ground. Next we use a vibrating hammer. It works for us from a 220V network. We attach the impact device of the vibrating hammer to the platform of the rod, turn on the hammer and hold this alignment, literally in 20 seconds, we sink the rod the entire length into the ground, leaving 20 cm above the bottom of the hole to connect it with another rod.
Measuring intermediate spreading resistance
We remove the landing pad from the pin and measure the spreading resistance. We connect the F4103-M1 device to the installed rod. The resistance at a depth of 1.5 m was, say, 485 Ohms.
To achieve a given spreading resistance, the modular pin system suggests deepening the vertical pins by building up grounding sections on top of each other. We carry out everything according to the recommendations of the instructions.
Installation of subsequent vertical modular pins
We treat the coupling with paste and screw the second copper rod into it, screw the second coupling onto the rod, treat it with anti-corrosion paste, and fasten the mounting head again. We apply a vibrating hammer to the device and repeat the previous process. We control the resistance to spreading.
We will carry out the process of building up the rods until the spreading resistance reaches a value of less than 4 ohms. When performing this process, we will not forget to treat the connections of each ground section with a protective anti-corrosion paste. Finally, after installing the seventh rod, we obtained a spreading resistance of, say, 3.35 Ohms at a depth of 10.5 m.
Installation of a horizontal ground electrode in a modular pin system
Now we proceed to install the connection between the vertical grounding conductor and the horizontal grounding conductor. A brass clamp is used to connect the steel strip or cable to the rod. One component of the clamp is adapted to connect a pin, the other half is a seat for a steel strip or cable. We attach a brass clamp with bolted connections to the end of the rod protruding from the ground. We connect the horizontal grounding component to the same clamp: a steel strip or copper cable and also fasten with bolted connections. The cable (strip) and the pin are separated by a special separating plate, which is necessary to prevent the occurrence of bimetallic corrosion when dissimilar metals come into contact. After connecting the strip or cable bolted connections We process it with a special PREMTAPE tape. She provides additional protection from corrosion of the contact of the vertical and horizontal components of the grounding. See fig. 12
Rice. 12. Deep modular pin grounding system
The ground loop, made using a modular pin system, can be configured as a single-point or multi-point ground loop, which will achieve the required ground resistance.
Advantages of a modular pin grounding system
Having drawn a graph in Fig. 13, showing the dependence of the spreading resistance on the depth of the grounding rod, let us summarize the work done. The installed grounding system achieved a spreading resistance of less than 4 ohms in less than an hour.
Fig. 13 Dynamics of changes in grounding resistance depending on the depth of the rod
Let's consider what conditions the installed system required? To make the ground loop using the modular pin method, it was necessary, firstly, to use a vibrating hammer to save the installer the effort; secondly, a measuring device and, thirdly, a second assistant assembler to support the rod while the vibratory hammer is in operation.
We establish what are the advantages of a modular pin grounding loop system compared to the generally accepted and widely used classical grounding loop.
- The modular pin system occupied an area of less than one square meter, that is, the limited installation area is not a hindrance to it.
- There is no exhausting excavation work, everything is done with one vibratory hammer.
- No welding is required, all connections in the modular pin system are made using couplings.
- Long service life, more than 30 years, thanks to anti-corrosion coatings and lubricants, that is, high resistance to soil and electrolytic corrosion.
- The use of a deep modular pin system makes it possible not to depend on the characteristics of the soil.
- The design is simple and installation is accessible to everyone; even one person can handle it.
Of course, the question will arise about the cost of such a system. The cost of equipment for installing a ground loop using a modular pin system will be approximately 500USD. The cost of installation of the system will be 120 USD. A classic grounding system based on materials will cost 100 USD and installation work is estimated at 120 USD. But I want to say that, although the classic system is cheaper, all seven of the advantages listed above justify the cost of installing a modular pin grounding system.
After completing the installation of the ground loop, it is necessary to draw up documents: measurement protocol; act of hidden work; grounding passport with diagram. All this must be kept by the owner.
Fig. 14 grounding passport
Conclusion
I shared with you my experience in choosing a grounding method. Now you know how to quickly and at a high technical level protect yourself and your loved ones from electric shock, and your home from fire.
Attention! The prices in the article are outdated.
