Reliable technical methods of protection against electric shock are considered to be grounding and zeroing. The protective grounding system is designed to electrically connect an object from a conductive material to the ground. The grounding and the grounding conductor connected among themselves act as components of grounding. The protective function consists in the complete or partial protection of a person against the threat of electric shock, in reducing the potential difference of a grounded conductive object and conductive objects with natural grounding to a safe value. Separate parts of the installation are connected to a grounded device through a resistance several times less than the resistance of the human body. When a short circuit occurs, most of the current passes through the earth, and the current that falls on the body turns out to be quite insignificant. If the grounding system is designed correctly, in accordance with the rules and regulations on technical operation, the occurrence of a current leakage leads to an immediate triggering of protective devices.
What are protective conductors (PE-conductors)
Zanulenie also performed for electrical safety. This is the process of deliberate electrical connection of the conductive open parts of electrical installations with a tightly grounded point. The zero PE conductor is used in this case to connect the open parts of the user of electrical energy to the grounded neutral point of the source.
Conductors for protective earthing, neutral protective conductors in electrical installations with a voltage of up to 1 kV with a dead earthed neutral are marked with the letter PE. The protective PE conductor is intended solely for electrical safety purposes. In a grounding system, PE conductors provide a continuous connection of all open and external conductive parts of an installation. The conductors ensure the creation of a continuous equipotential system and ensure safety. PE conductors facilitate the passage of current caused by damage to a grounded neutral source. PE-conductors are connected to the main grounding bus of the installation, which, in turn, is connected to the grounding electrode by a special conductor. The color designation of conductors (PE) corresponds to alternating transverse or longitudinal stripes of the same width of green and yellow colors. PE conductors must be carefully protected from all kinds of mechanical and chemical damage. They are laid in one pipe, cable channel, cable niche with current-carrying circuit cables in the grounding circuits of IT and TH. This feature provides the lowest possible inductive resistance of the circuit through which the short-circuit current flows to earth.
In electrical installations with a voltage of up to 1 kV, specially provided conductors are used as PE conductors. But these functions can also be assigned to open parts of electrical installations or some third-party conductive parts. If we are talking about specially provided conductors, they can be:
- multi-core cable conductors;
- both insulated and uninsulated wires;
- conductors laid stationary.
The functions of PE-conductors can perform open parts of electrical installations:
- aluminum cable sheaths;
- steel pipes electrical wiring;
- metal shells of busbars;
- supporting structures of complete devices.
The functions of PE-conductors can be performed by third-party parts with high conductivity, such as:
- metal frames of buildings, metal constructions;
- reinforcement structures;
- designs for industrial purposes.
Metal ducts, trays of electrical wiring, perfectly suited as conductors. In the process of designing the construction, it is necessary to exclude any mechanical damage to these structures and to foresee their use as conductors.
Open conductive parts, as well as third-party conductive parts, are quite suitable as protective PE conductors, if they meet all the requirements of this chapter of electrical conductivity and continuity.
If it becomes necessary to use third-party conductive parts as conductors, they must meet the following requirements:
- their design must be made in such a way as to ensure the continuity of the electrical circuit. If this possibility is limited to certain construction features, the continuity of the electrical circuit must be ensured by means of connections protected from any kind of damage;
- if there is a minimal risk of interrupting the continuity of the chain, then dismantling such structures is impossible.
For safety reasons, one should not forget that some devices are strictly prohibited for use as PE protective conductors. This is about:
- metal sheaths of insulating tubes, hoses, lead sheaths of cables;
- central heating pipes;
- sewer pipes;
- water pipes;
- gas supply systems.
In many old homes, electrical wiring is done according to long obsolete standards and needs to be replaced. To ensure their own safety, residents of such houses are trying, with the help of experienced electricians, to modernize. The task is to divide the previously combined zero and working PEN conductor into zero protective PE and zero working N conductors. This requirement ensures maximum security, reliably saves ground connections to the protective conductor in the event of a break in the contact clip.
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