Electrics

The earthing circuit - the device, calculation and installation of grounding system for a country house

ground Circuit

With the development of technology mnogomoschnyeelectrical appliances flooded our homes. Even hard to imagine life without a refrigerator, washing machine, microwave oven, induction cooker - after all, we use every day. Do not forget that electric appliances are dangerous for us in case of violation of their isolation. Therefore, it is imperative to equip a ground loop for the entire house, thereby having secured yourself and equipment from short-circuiting.

Content

  • What is the ground loop
  • Ground loop device
  • How to make payment
  • Grounding circuit: circuit
  • Construction of ground loop

What is the ground loop

Explain to dry their technical language, groundingmeans electrical connection to earth (ground) live elements of electrical installations, made intentionally. The data of the appliances are not live in a normal condition, but may be under him. The reason may be a violation of the insulation as well.

To explain a simple and accessible language,We have to remember high-school physics. As we remember, the current tends to flow in the direction of least resistance. If the insulation of live parts broken equipment, the current will find a place in which the resistance is the lowest. So there is a breakdown in the body of the appliance. In other words, metal body will be under stress. In addition, it can disrupt the device itself, or even break it, if you are currently a person touches a surface of the housing, it will get an electric shock.

ground loop needs to currentdistributed between a man and a grounding device is inversely proportional to their resistance. Given that the human body's resistance is much greater than the resistance to earth loops flowed through the maximum allowable current, and the rest goes into the ground. We have come to a very important point: performing circuit ground with their hands, You must make it so that its resistance was minimally acceptable.

Here is the ground loop

Circuit ground is performed by means of steel rods, to a depth of slaughter, and straps, their sodinyayuschih

Ground loop device

Most often performed using groundingmetal rods - electrodes buried in the ground and interconnected top strip or rod. This structure houses adjoining the flap is connected to a cable or a metal strip.

The actual depth of electrodes depends on the saturation of the soil with water. The above are the ground water, the lower the required depth.

The distance from the house should be at least 1 m, but not more than 10 m.

Dimensions of earth

The minimum allowable size of fittings used for the installation of grounding devices

Circuit private home ground is performedusing rods, as which can act steel corner fittings with smooth structure, pipe, double tee. sectional area of ​​the electrodes must be greater than 1.5 cm2, and should be convenient form for driving into the ground.

The rods are arranged in a row or in ageometric shapes: triangle, square, rectangle. It depends on the design and ease of installation space that can be used. It is also possible circuit equipment of the building perimeter. But the most popular continues to be a triangular contour ground. The tops of the figures hammered electrodes which are interconnected by a steel band.

Important! earthing circuit must necessarily be placed below the freezing ground.

In other words, the ground can be doneusing improvised material. But it is possible to buy a ready set of everything for the ground loop. It consists of rods - the electrodes of copper plated steel, 1 m long, threaded connections combined. These kits are not cheap, but much easier task and durable in use.

How to make payment

Of course, you can perform an experienced groundmeans. For example, to determine the depth of water abundance, to retreat from the house at the optimal distance and to arrange a triangular contour. Cook the electrodes to each other and measure the resistance of the resulting structure. If it is too large, bury more additional electrodes, attach them to the previous one and take measurements again. And so long as the measurement result will not meet the requirements.

Experts also strongly recommend tohow to make a ground loop, make all the necessary calculations. Determine the number of vertical earth electrodes - electrodes, which is required, and the length of the connecting bars, depending on the soil resistance.

For starters need to determine the resistance of a single vertical grounding - electrode.

The resistance value of vertical earthing

Formula 1. Resistance of vertical earthing

Where,

R0 - resistance of the electrode, Ohm;

Rekv - the equivalent soil resistivity, Ohm * m;

L - length of the electrode, m;

d - diameter of the electrode, mm;

T - the distance from the center electrode to the ground surface, m.

The values ​​of soil resistivity

Table 1. The soil resistivity

Seasonal climatic soil resistance coefficient

Table 2. The value of the seasonal climatic soil resistance coefficient

The value of earth resistance can be taken from the table, but if the ground is nonuniform, then

Ekvivaletnoe soil resistivity, if inhomogeneous

Formula 2. Ekvivaletnoe inhomogeneous soil resistivity

Where,

Ψ - Seasonal climatic factor;

P1, P2 - soil resistivity (1 - the upper layer, 2 - the bottom layer), Ohm * m;

H- thickness of the top layer of soil, m;

t- depth to which the electrode is clogged, m (trench depth);

If you do not take into account the horizontal resistance earthing, the number of electrodes can be found by the formula:

The formula of finding the number of electrodes

Formula 3. The amount of the electrodes excluding the horizontal earth electrode resistance

Where,

n0 - the number of electrodes;

Rn- normable grounding resistance based on the PTEEP.

table of correspondence

Table 3. The highest allowed value of resistance of grounding devices (PTEEP)

Determine the resistance of the current horizontal earthing according to the formula:

The formula for finding the horizontal earthing current resistance

Formula 4. current resistance spreading horizontal earthing

Where,

Lg - The length of the earth electrode;

b- width of the grounding;

ψ - The seasonality factor of horizontal earthing;

ɳG - Coefficient of horizontal earth electrodes demand.

earthing Length is as follows:

The formula for finding the length of the horizontal earthing

Formula 5. The length of horizontal grounding

Where,

a - the distance between the electrodes.

Resistance to vertical electrodes based on a horizontal earth electrode:

Formula finding vertical earthing resistance

Formula 6. Resistance vertical grounding - electrode based on a horizontal earth electrode resistance

The total number of vertical grounding - electrode is:

The total number of electrodes

Formula 7. The final number of vertical earthing

Where,

ɳv - Coefficient of demand vertical earthing.

The value of using the coefficients of earth

Table 4. The utilization of earth

The indicator called "factorUse "shows the influence of the currents at each other depending on the location of the vertical electrodes. If the electrodes are connected in parallel, the currents flowing on them affect each other. The shorter the distance between the electrodes, the total circuit resistance is greater.

If the number of earth, resulting in the last formula is not an integer, it is rounded up to the next higher integer.

Grounding circuit: circuit

After all the calculations are made, choosea convenient place for the location of the grounding circuit. Determine which figure will be placed electrodes. Then draw a ground loop circuit according to the type of materials used. Be sure to specify that used for the electrodes and the connecting band, their length and diameter, depth.

Scheme of ground loop

Grounding circuit: circuit in the data sheet (outside the building) - example

Scheme of ground loop

Grounding circuit: circuit in the data sheet (inside the building) - example

All these come in handy not only for convenience,installation and for the future, but in order to get a ground loop passport. When the installation work will be completed and measured loop resistance, energy management staff who need to be invited, will be given Sight and all necessary documentation to the contour of the ground. Of course, in this case, if done correctly.

Construction of ground loop

Installation of ground loop is better to start in a warmseason. So it will be easier to excavate and measure the resistance of the ground. At the same time will be seen more accurately, the depth at which the groundwater occur.

Consider the case of ground loop arrangement in the form of a triangle:

How to make a ground loop in a private house

For the arrangement of the ground loop you need to dig a trench to a depth of soil freezing

  1. The place we have chosen. So dig a trench depth of 0.7 m to 1 m (below freezing soil), a width of 0.5 -. 0.7 m lines should form a triangle with the side, the length of which has been determined in the course of calculations.
  2. From one of the angles of a triangle digging a trench in the direction of the power panel.
  3. At the apex of the triangle trying to drive grounding -electrodes. What exactly will be used for this purpose, it is necessary to decide at the stage of settlement. Suppose as an example it will steel bracket 50 * 50 mm. If the density of the soil does not allow a goal rods have to drill wells.
  4. Bury the rods so that they protrude above the ground. When we still had to drill wells, install them in the corners and covered with soil, mixed with salt.
  5. Take the steel strip 40 * 5 mm and welded to the electrodes, forming a triangular contour. Then, one of them to force the strip conducting enclosure.
  6. The band anchoring to the ground wire or power board with a bolt diameter of 10 mm. In this case the bolt welded to the band definitely.
  7. At this point, we check the loop resistanceOhmmeter ground. The device that is not cheap, it does not make sense to buy. It is better to invite employees of energy management that they took measurements and filled the ground loop passport. resistance index should be less than desired. If not, then you need to drive additional electrodes.
  8. If the resistance was sufficient fall asleep trench uniform ground without construction waste and rubble.

Important! During further operation of abnormally dry weather in the ground loop is desirable to pour water from the hose in order to reduce its resistance.

All work related to the calculation and installationground loop can be entrusted to professionals who have more experience. This can save you time and hassle. But if you tend to do everything with your hands, go for it. Your creation will serve as a protection for you and your family.

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