What is grounding, how does it work and what is it for

The power grid is the foundation of the modern world. Almost all modern household appliances are powered by electricity, because it is a convenient source of energy. But there is a flip side to the coin - a high risk of electric shock. Without the right approach to equipment design and network design, electricity will do more harm than good. Grounding is one way to ensure safety.

In simple words about grounding

Grounding is a complex of solutions and devices for protection against electric shock and ensuring the operation of protective equipment.

Domestic power networks have dead earthed neutral. What does it mean? If we consider this issue in a simplified manner, then three-phase generators are installed at power plants. Their windings are connected according to the star scheme. The connection point of the windings is neutral.

If you ground the connection point of the star, as shown in the figure above, you get a power line with a grounded neutral. The potential of this point and the neutral wire will be equal to the potential of the earth.

The grounding device is called earthing switch. Usually these are three metal pins killed in the ground at the same distance from each other, being as if at the vertices of a triangle, while they are interconnected by a steel strip by welding. The length of the pins and their cross section is calculated for specific conditions and requirements for this object.

Next, the main busbar grounding is brought into the building and conductors are laid from it to the electrical panels and to the electrical equipment.

The grounding conductor is inserted into the electrical panel of the house or apartment and connected to the grounding bus. It is a metal strip with terminal blocks. Earth conductors from each grounded device or outlet are connected to it. If the device is not connected via an outlet, then a grounding conductor is laid to it, and it is connected to a special terminal connected to the housing.

All grounding conductors and busbars are insulated or painted with alternating stripes of green and yellow.

In appearance, grounding is protective and working. As you might guess, protective grounding performs the functions of protection against electric shock, and the working one is necessary for the normal functioning of electrical equipment.

Thus, grounding is called the electrical connection of the body of electrical appliances with an earthing switch.

Why is it shocking?

To understand why grounding is needed, first we will understand in what cases and why we are shocked. The main thing that is necessary for the flow of electric current is the potential difference.

This means that if you are standing on the floor and grabbing a bare wire or other live part with your hands, then the current through your body and floor will drain into the ground.

Attention:

An alternating current of only 50 mA is already dangerous to humans.

And if you hold onto the live part with both hands and hang on it without touching the ground, then most likely nothing will happen, it’s certainly not worth checking it. Therefore, birds are not shocked by wires. But back to the conversation about grounding. As we have already said, the housings of electrical appliances are grounded. What is it for?

Wiring and other components of the equipment, such as electric motors, electric heaters, etc. in normal condition do not have phase contacts with the device body, metal hose or cable armor. But in case of malfunctions, the phase may appear on the case.This can happen if insulation of the windings of motors and transformers is damaged, breakdown of the dielectric layer of the heating elements, damage to the insulation of the connecting wires inside the device and cable lines.

As a result, the housing will have a dangerous potential, in simple terms: the housing will be "under phase". When you touch it while standing barefoot on a tile, concrete and even wooden floor - you will be shocked. In the worst case, this can lead to death.

Most often this situation arises as a result of partial failure of heating elements of washing machines, water heating tanks, flow heaters. And this is especially vividly felt when you simultaneously touch the washing machine and water and heating pipes, or in the case of a water tank, when you take a shower or bath, it is shocking.

The last problem is solved by the organization. potential equalization systems (grounding the bathtub and other metal parts of the water supply).

If the case of the damaged device is grounded, hazardous voltage will drain to the ground and (or) the protective device will trip - residual current device (RCD) or residual current circuit breaker (difavtomat). We have already considered what kind of devices they are and how they work in the articles earlier:

Types and types of RCD

How to distinguish electronic RCD and electromechanical

The device and principle of operation of difavtomatov

Schemes for connecting RCDs and differential machines

If the body is zero, it will work ordinary machine, as this will be a short circuit to the case (zero in this case). Difavtomats and RCDs determine the leakage of current by comparing the currents of the phase and neutral wires - if the current in the phase is greater than zero, then the current flows into the ground, through the ground wire or through the human body. Such devices operate at a differential current (current difference), usually 10 mA or more.

therefore modern electrical panel - This is a complex device with a large set of switching protective devices, and the presence of grounding is mandatory in all buildings built or renovated after 2003. That is, they must be laid 3-wire single-phase or 5-wire three-phase wiring. If you want to express your opinion on grounding issues, write in the comments about this.