Devices in a metal enclosure that consume electricity may be energized if the insulation is damaged. This poses a danger to human life. To prevent electric shock, a protective earth ground is used, which removes potential from the instrument housings.
What is protective grounding for?
The essence of protective grounding is to create a connection between the metal elements of the equipment and the ground. In the normal state, the devices are not energized, but the situation changes when insulation damage occurs in one of the sections of the circuit. A deliberately designed protective circuit helps prevent accidents.
Electrical standards require that protective grounding be performed in all areas where there is an increased risk of electric shock, as well as in outdoor installations where voltages above a certain level are used. Grounding is mounted in such a way that it can provide a connection to the ground for all equipment frames, secondary windings of transformers, cable sheaths, and drives of electrical units.
Reliability of grounding is ensured by creating an effective electrical connection with low resistance. In this case, at the moment a person touches the body of the device, the current will not flow through the body and will not cause a life-threatening injury. For the current to flow through the ground, it is necessary to have a permanently closed circuit, which will ensure the creation of a protective grounding system.
How does protective grounding work?
High-quality protective grounding is performed in two ways: using artificial conductors laid for the grounding network, as well as using natural elements, which can be metal structures that initially perform a different purpose. From a structural point of view, the protective earthing elements are in the ground or protrude from it. In the latter case, the details of the structure must be clearly visible, for which they are usually painted black.
The protective earthing system has two parts. The first of these is soil, which is assessed by its resistivity. This characteristic is determined by the degree of moisture in the earth and its temperature. During the year, soil resistivity can vary significantly, affecting the protective function of the grounding system.
Another part of the system is ground electrodes, that is, one or more electrodes connected to each other. These elements are constantly in the ground, which guarantees reliable contact between the objects to be grounded and the ground. A group of elements, which includes several metal grounding electrodes, forms a single system called a ground loop.
