Grounding devices. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Grounding devices. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Grounding and grounding

The protective effect of grounding is based on the fact that parts of electrical installations that are dangerous to touch if the insulation is broken are connected to ground electrodes located in the ground, i.e., a ground is created that has a resistance that is small enough to cause the voltage drop across it (and it is it that affects the body, determining the value of the current) did not reach a dangerous value. Therefore, a person who touches the grounded part falls under low voltage. The better the grounding, i.e., the lower its resistance, the lower the voltage that appears when the insulation is broken on machines, machine tools, housings of electrical appliances and motors, building structures, overhead line supports and on the surface of the earth.

It is clear that this increases the cost of labor and materials required for the installation of a grounding device. The regulations set reasonable limits for the touch voltage and at the same time allow the design of earthing without excessive costs.

The SNiP, PUE, Rules for technical operation and instructions list in detail the elements of electrical installations that need to be grounded, provide instructions for calculating ground electrodes and contact voltages for different conditions, list the requirements for the design, installation and operation of grounding devices.

The characteristic and fundamental features of the standards are:

departure from the standardization of grounding devices according to the resistance of the spreading of electric current and orientation towards the regulation of emerging voltages;
the use of natural grounding conductors while ensuring their performance under conditions of high fault currents;
taking into account the corrosive effect of the soil to ensure the reliability of grounding conductors and grounding conductors.

With this in mind, the dimensions of the elements have been increased, for example, the standard minimum diameter of earth rods made of non-galvanized steel has been increased from 6 to 10 mm.

The norms are constantly being improved, changes and additions are made to them, which are published in collections and new editions of normative documents.

Very often, the same grounding device is both working and protective, and sometimes lightning protection (lightning protection). In closely spaced installations with voltages up to 1 kV and above, a common grounding device is used, which reduces the cost of its installation. In this case, the smallest value of resistance to current spreading from those values that are normalized for each of the combined electrical installations is taken as the norm.

The combination of a grounding conductor and grounding conductors is a grounding device through which the elements and parts of electrical installations are grounded.

The main elements of grounding devices:

1) natural grounding conductors, i.e., structures located in the ground or in contact with the ground, used for grounding;

2) grounding conductors connecting ground electrodes with grounded equipment;

3) artificial ground electrodes, i.e. those that are specially laid in the ground for grounding.

Each of the listed elements can have different designs.

Author: Bannikov E.A.

See other articles Section Grounding and grounding.

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