How to calculate the parameters of the main grounding elements
Based on the results of such calculations, a drawing of the grounding device of the facility is designed.
Important! The device, mounted in accordance with all the calculated data of the grounding scheme, allows you to achieve maximum operational efficiency of the entire protective grounding complex. The basis of the calculations is the permissible limits of step and touch voltage. Based on them, the configuration (size, number) of grounding conductors and the principle of their placement are calculated
Based on them, the configuration (size, number) of grounding conductors and the principle of their placement are calculated
The basis of the calculations is the permissible limits of step and touch voltage. Based on them, the configuration (size, number) of grounding conductors and the principle of their placement are calculated.
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Calculations are performed based on the following data:
- Description of the characteristics of specific electrical equipment: installation type; main structural elements of the device; operating voltage; Possible options that allow grounding of neutrals of both transforming and generating devices.
- Grounding configuration. Such data is necessary to determine the optimal immersion depth of the electrodes.
- Information about studies conducted to measure soil resistivity in a specific area. Additionally, the climatic information of the zone in which the system is being installed is taken into account.
- Information on suitable natural earthing elements that can be used in your work. Data are needed on the real values of current spreading in these objects. They can be obtained by special measurements.
- The result of a standard calculation of the exact indicators of the estimated current short circuit on the soil.
- Calculated values of regulatory standardization of permissible voltage characteristics according to PUE.
- Indicators of resistance to seasonal freezing of the soil layer during the period of drying and freezing. Taking into account such values is necessary for calculating grounding elements that are located in a homogeneous environment. Special standardized coefficients are applied.
- If it is necessary to install a complex group of grounding conductors, consisting of several elements, it is necessary to know all the potentials that will be induced on the mounted electrodes. To do this, we need data on the resistance values of all soil layers.
Important! If the system is placed in two layers of soil, the resistance value of each of them is taken into account. This is necessary to determine accurate data on the power parameters of the top soil layer
Controlled memory parameters
Reliable operation of the entire mechanism depends on the total resistance of the grounding circuit. It, in turn, is formed due to the connecting busbars and the design of the ground electrode itself. Reducing the value of this value entails the safe operation of devices and all equipment for which protection is provided. The process of arranging grounding loops is carried out by selecting appropriate forms of structures, thereby artificially increasing the area of interaction of key elements with the soil. Grounding devices are also measured.
The same result can be achieved by specifically increasing the percentage of salt content in the ground that has direct contact with the metal part of the ground electrode. This method will reduce the resistance to the flow of electricity into the soil, which will increase the level of reliability of the functioning of the mechanism circuit.
In order to control the value of all indicators, it is necessary to organize maintenance of the grounding system and conduct tests of grounding devices. They require mandatory measurement of the specified parameters. If significant deviations from the requirements of the PUE are found, it is necessary to inspect the grounding device, repair it, and then check the grounding resistance a second time.
Primary requirements
Most of the relevant recommendations and rules regulate the design and placement of such a component of the grounding system. Requirements that an artificial grounding system must meet:
- For arid areas, there is a separate technology for grounding using reinforced concrete structures.
- The artificial grounding conductor cannot be painted. This is explained by the fact that any coloring acts as an insulator. The insulation will prevent current from flowing into the soil. The artificial grounding conductor must have a natural color.
- Welding seams (conductor connections) must be painted. Painted with bitumen paint, premature destruction of the connecting elements is prevented.
- Non-standard (reduced) electrode values are used exclusively when installing temporary electrical installations.
The optimal choice of grounding material is considered to be round reinforcement. Justification for this priority:
- Minimum metal consumption. Consequently, the cost of the grounding device is reduced.
- The corrosion resistance of such an electrode is significantly higher than that of its analogues.
- Ease of installation.
In addition to the profile requirements, there is a recommended standardization of the parameters (dimensions) of the material used to create an artificial grounding element.
Ground electrode depth
...from the collection “Grounding: Answers to Questions”
…Everywhere there is information that the corners (vertical) should be 2.5 meters long. We have 6 meters long for sale at the metal warehouse. I’m thinking of sawing it with two cuts into pieces of 2 meters each. And hammer them in at a distance of 2 meters from each other... Question. Is it critical that it is 2 meters and not 2.5 meters? Or do you need 2.5 m?
The soil is gray clay, always damp. Will I meet the required parameter limit (30 ohms)?======================================================= Not critical
