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.
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.
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.
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.
Table 1. The soil resistivity
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
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:
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 3. The highest allowed value of resistance of grounding devices (PTEEP)
Determine the resistance of the current horizontal earthing according to the formula:
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:
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 6. Resistance vertical grounding - electrode based on a horizontal earth electrode resistance
The total number of vertical grounding - electrode is:
Formula 7. The final number of vertical earthing
Where,
ɳv - Coefficient of demand vertical earthing.
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.
Grounding circuit: circuit in the data sheet (outside the building) - example
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:
For the arrangement of the ground loop you need to dig a trench to a depth of soil freezing
- 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.
- From one of the angles of a triangle digging a trench in the direction of the power panel.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
