Build Daily

December 12, 2017 00:15

How to make ground loops

It has long passed the time when the presence of protective earth was the prerogative of exclusively industrial enterprises. With the growing number of household appliances in our home, protective earthing has become an indispensable attribute of any private home. And this is not surprising. Any violation in the insulation of electrical appliances can lead to very serious consequences for the inhabitants of the house.

Contents

The best way to protect yourself is to equip the ground. There is no need to attract professionals to the device of the grounding loop. Anyone can fully cope with this task. The main thing - patience and attention during work.

Designation and installation of the ground loop

Protective earthing is a connection between live parts of electrical installations and the ground, made intentionally.

In normal operation of electrical appliances, their housing is not under voltage. Working with such devices is safe. Unfortunately, the more devices, the higher the probability of any of them failing. The slightest damage to the insulation layer - and the case of the device will be under tension. Touching such a device is deadly.

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It is these situations that prevent the protective grounding. Everyone knows that the electric current flows to the side with the least resistance. The presence of a ground loop in a private house with a low resistance value is a guarantee that the current will go to the ground.

The most common version of the ground loop is the electrodes buried in the ground. They are connected together in the form of a closed contour of a certain shape. A triangular shape of the contour is often used. It is possible to make a ground loop along the perimeter of the building. Among the main criteria for choosing the shape of the contour are the convenience of its installation and the size of the territory used for its construction. The earthing loop is connected to the electrical panel by means of a special earth cable.

The optimal distance between the house and the ground loop is 5 m. The distance is closer than 1 m and further 10 m is considered to be unacceptable.

Tip: The minimum depth of the ground loop is 0.8 m. The contour placed within the freezing limits of the soil does not work in winter.

Electrodes are buried in the soil for 1,5 - 3 m. The choice of depth for each individual case depends on the structure of the soil and its humidity. The more the soil is saturated with water, the less the electrodes are buried.

Materials required for installation of the grounding loop

Typically, the ground loop is made from improvised materials. A grounding electrode is capable of serving any rod made of ferrous metal. The choice is very wide. The main criterion is convenience when plugging into the ground. Steel corners are mainly used. It is possible to use valves of a smooth structure, pipes, I-beam. The only requirement is a cross section of metal from 1.5 cm2.

To determine the number of required electrodes, calculations are extremely rare. Mostly they use an experienced way. The most common number of electrodes is three. Thus, we obtain a triangular ground loop. The vertices of the triangle are the electrodes. The distance between adjacent electrodes of less than 1.2 m is inadmissible. It is calculated based on the resistance of the soil. The electrodes are interconnected by means of metal strips. A similar band also serves to connect the circuit with the distribution circuit. 2

Before installing the ground loop, always consult a qualified electrician who lives in the same area. A similar expert from experience knows how to make a ground loop ideally suited to the area:

  • what should be the distance from the building to the circuit;
  • what should be the distance between adjacent electrodes;
  • number of required electrodes;
  • depth to which electrodes should be clogged;
  • depth on which to place the outline.

The undeniable advantage of a self-made earthing system is its low price.

It is not necessary to make a ground loop only from improvised materials. On sale there were special ready-made earthing systems.

The set of modular earthing systems consists of the following:

  • rods made of high-quality steel and coated with copper. The length of the rods is about 1.5 m, the diameter is 0.14 m. Each rod is provided with a sliced ​​copper thread;
  • brass couplings for connecting the elements of the ground loop;
  • tips. Facilitate the clogging of the rod in the ground. Fastened to the stem by thread. There are tips of several kinds. Designed for various types of soil;
  • clamps for connecting horizontal elements to vertical ones;
  • anti-corrosion paste for the treatment of all elements of the grounding system.

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Advantages of modular earthing systems:

  1. Rods made of stainless steel and coated with copper are less susceptible to corrosion.
  2. No need for welding.
  3. No special equipment required for installation.
  4. Space saving. To equip the entire system, 1 m2 is enough.
  5. Longevity.

Earthing calculation

No matter which version of the grounding system is selected, the preliminary calculation of the grounding parameters is a mandatory step. Usually grounding is done by experiment. This method will help to avoid a lot of complex calculations.

The algorithm for installing the ground loop in this case is as follows:

  • We construct a triangular ground loop at a distance of 5 m from the house. The length of the electrodes is 3 m, the distance between them is 2 m. We use metal rods.
  • We connect the electrodes to each other.
  • We measure the resistance of the ground loop. To measure the resistance we use a special device - an ohmmeter. The maximum permissible resistance of the ground loop is 10 Ω.The optimum value is 4 ohms. Compare the result with the optimal value.

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  • If the resulting resistance value does not match the optimal value, add one more electrode to the circuit.
  • Connect all the electrodes to a new circuit.
  • We again measure the resistance of the circuit.
  • Repeat the above procedures until we achieve the value of the loop impedance of 4 ohms.

It is possible to determine the number of required electrodes and the length of the horizontal earthing electrode by means of calculations:

  • If there is a uniform ground in the area, determine the resistance of one electrode using the formula 1:

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To determine the resistivity value of the soil, use Table 1.

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If there is an inhomogeneous soildetermine the resistance of one electrode according to the formula 2:

7th

The values ​​of seasonal climatic coefficient are given in table 2:

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According to the formula3 determine the required number of electrodes without taking into account the resistance of the horizontal earthing switch:

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To determine the standardized earth resistance, use Table 3:

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Define the resistance of the horizontal earthing electrode by the formula 4:

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. To determine the length of the earthing electrode, use the formula 5:

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Calculate the resistance of the electrodes taking into account the resistance of the horizontal earthing electrodeaccording to the formula 6:

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Define the final number of electrodes required for the contour device groundedI:

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To determine the demand factor vertical earthing use Table 4:

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The final value of the number of electrodes, obtained as a result of the above calculations, is rounded to a larger integer. What method to use - experienced or calculated - is a private matter for everyone. Choose any, based on your own preferences.

How to make a self-ground loop

After all the preliminary calculations and preparation of the necessary materials, proceed directly to the installation of the ground loop.

Tip: The best time to install a ground loop is summer. And not only because of the fact that in the warm season it is easier to excavate. The fact is that in dry ground resistance is greater. Having achieved the optimum value of resistance in dry weather, do not worry about the deterioration of this indicator in the future. On the contrary, with increasing soil moisture, resistance will decrease.

Let's consider the basic stages of installation of a triangular earthing circuit, the circuit of which is shown in the figure.

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  • At a distance of about 5 m from the house in a convenient location, dig a trench as an equilateral triangle. The depth of the trench is about 1 m, the width is 0.5 m. The length of the side of the triangle should correspond to the calculations made earlier. From any angle to the switchboard of the house, dig a trench.

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  • Insert the electrodes into each of the vertices of the triangle. The ends of the electrodes must first be sharpened with a bolgar.
  • With very hard ground, first drill the wells under the electrodes. Inserting the electrode into the well, fill it with a mixture of soil and salt.
  • Do not immerse the electrode completely in the ground, leave the tip above the ground.
  • Connect the electrodes with a steel strip, a width of at least 40 and a thickness of at least 5 mm. To attach the electrodes and strip, use welding.
  • Connect one of the electrodes to the switchboard by laying an identical steel strip in the previously prepared trench.
  • Connect the strip and the switchboard using a 10 mm bolt. Be sure to weld the bolt to the shield.
  • The next step is to measure the ground loop. Use an ohmmeter to measure.
  • If the measurement result corresponds to the optimum resistance value, the ground loop is mounted correctly. You can start digging in trenches.
  • If, however, when measuring the ground loop, it turns out that the resistance exceeds the standard value - add one more electrode.
  • Use a very uniform primer for digging a trench. The presence of impurities of crushed stone and construction debris is unacceptable.
  • The ground loop is ready.