The grounding of electrical installations is of two main types - protective and operational. In the regulatory documents of the Ministry of Energy, the definition of working grounding is as follows: grounding points conductive elements of an electrical installation is called working if it is not created for the purpose security. This is how it differs from the protective one, which must first of all ensure safety.
Content
- Purpose and principle of operation
- Differences between types of grounding
- Design features
- Simultaneous application and general rules
- Security measures
Purpose and principle of operation
A working or functional ground is created not for protection, but for the normal operation of the installation. When creating it, make sure that the installation is in contact with the ground. The main purpose is reducing to zero the likelihood of electric shock when a person comes into contact with the body of the installation or with its conductive elements that are under high voltage.
This protection is used in power grids with a 3-phase electrical distribution system.
An insulated neutral conductor is needed for an electrical network that is less than 1000 volts. In those networks, the voltage of which is more than 1000 volts, it is possible to use any neutral mode.
The voltage is reduced between the body of the electrical installation and the ground. Its value becomes less dangerous. In the event that the body of the electrical installation does not have a working ground, touching it will lead to the same consequences as contact with the phase wire. Given that the electrical resistance of shoes and the floor is small compared to that of the soil, the current can become dangerous.
If everything functions correctly, then the current that will pass through the human body will not cause any harm. The voltage in this case will also be small: almost all the energy will go into the ground. This is facilitated by the grounding conductor - in another way it is called the grounding conductor.
Differences between types of grounding
There are significant differences between working and protective grounding. The main one is the purpose. While the worker ensures the normal functioning of electrical equipment, protective grounding is called protection against electric shock. In addition, it helps protect equipment from failure in the event that the case is accidentally punctured. If the building has a lightning conductor, then the protective resistance will prevent possible overload during a thunderstorm.
Working grounding of electrical installations during an emergency will protect the devices themselves and the person, but its main purpose is to ensure the correct operation of the equipment.
Working grounding is used only in industrial enterprises, and in residential buildings, a grounding conductor is installed, connected to the outlet. But still, there are electrical appliances that are fraught with a possible danger, so it will not be superfluous to ground them using a dead-grounded neutral.
Design features
Working grounding is metal rods installed in the ground. They play the role of conductors of electric current and are able to divert electricity into depths of several meters. These iron rods are the connecting elements between the ground bus and the terminals of the electrical equipment. As a result, a metallic bond is formed.
There is such a connection in every residential building. With its help, the tops of the ground electrodes are connected. She starts up to the introductory panel and then divorces all apartments. The role of the grounding conductor in this design is played by a bus or wire, the cross-sectional area of which is at least 4 square meters. mm.
Simultaneous application and general rules
An electrical installation will not be sufficiently protected if it is equipped with only one earthing. There must be several earthing switches, since the ground is a non-linear conductor.
The electrical resistance of the soil largely depends on the magnitude of the voltage and from the contact area with the rods:
- If you use only one earthing switch, then the contact area will be small. It is not enough to keep the electrical installation running smoothly.
- If at least two earthing switches are installed at a sufficient distance from each other, then they will work effectively. It is best to install them at a distance of 1 to 2 m.
It is important to follow the rules of the PUE, according to which:
- It is forbidden to use pipeline elements as ground electrodes, regardless of the purpose of the latter.
- Do not lead the cable out and connect it to an ill-prepared contact pad on the bus. The fact is that any metal has a certain potential. Under the influence of various environmental factors, galvanic vapor begins to form, and this leads to corrosion.
- Do not alternately ground several electrical installations with each other.
You also need to remember: there should be only one cable per bus contact pad. If the rules are not followed, then during an emergency one installation will interfere with the normal functioning of the other.
Security measures
To protect a person from a current with a voltage of less than 1000 volts, it is necessary to ground all metal elements of electrical equipment. If a person is injured from the current, then a burn will remain on his body. Loss of consciousness or cardiac arrest may occur.
Very important, so that each design fully complies with safety requirements, which are presented to ensure the correct operation of power grids and fuses.
To protect people from electric shock, you must avoid contact with metal elements of the electrical installation. For this, complete isolation can be carried out. A protective structure built around the electrical installation will help in this matter.
