The discovery of the current marked a new era in the development of mankind. It is impossible to imagine a comfortable existence of a modern person without energy carriers. But a new kind of energy is a reliable servant only in cases of complete vigilant control. In order to avoid negative consequences, the following safety measures are used: protective grounding, grounding and automatic systems for de-energizing networks.
Content
- Concept and features
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The principle of the mechanism
- Protective grounding schemes and systems
- Features of grounding in the apartment
Concept and features
Grounding is understood as the connection of a metal case and other parts of household appliances and industrial equipment, which must not be in working order under the mains voltage line, to the neutral or neutral wire of the supply system energy. At one of the points, the wire must have a solid ground.
The difference between the neutral protective conductor and the neutral conductor of the main supply network is important. The conductors are completely different. A three-phase network is a neutral wire running from a device that generates electricity, or a power transformer substation. Single-phase has only a firmly grounded wire.
The main purpose of the mechanism is to organize the protection of people from electric shock in the event of a short circuit of the mains phase to the conductive parts of the installed equipment.
The principle of the mechanism
The presentation of the following situation will help to clearly explain the action of zeroing. The phase of the main supply network falls on the body of the electrical equipment, which can occur due to insulation breakdown or any other force majeure circumstance. If, in this case, the conductive part of the device has an organized protective neutralization, a short circuit will occur.
In this case, the current will reach its maximum value in a fraction of a second and the automatic protection system will operate. In some cases, the fuse may blow. The equipment itself or household appliances will be de-energized. This will protect the person from serious electrical injuries and will prevent any other negative consequences from occurring.
A prerequisite for the operation of the mechanism - very low resistance to current at the neutral conductor. It is in this situation that the fault current will rise to the maximum, which will cause the protective network system to operate. Since the neutral is provided with full grounding on the transformer or generator, grounding organizes, when touched, a low voltage on the case of the device used.
Protective grounding schemes and systems
There are several options for protecting equipment using a mechanism for neutralizing metal cases. The basic consideration involves examining the connections to the single-phase and three-phase power supply network.
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Three-phase network. It is characterized by a simple connection diagram, which anyone who is familiar with the elementary fundamentals of electrical engineering can do. In this case, the protective line P E and the neutral wire N are combined into a single bus - PEN. A similar technique for neutralizing is called the TN - C system. To implement the method, it is necessary to carefully observe the requirements for the equalization of electrical potentials and for the cross-sectional areas of the combined PEN conductors. The electrical installation rules strictly prohibit the use of the system for a network with a single-phase power supply. - Single-phase network. The TN - C - S system exists for the implementation of neutralization in a 1-phase network. According to the method, the PE line and the N conductor are combined only under conditions of limiting the power supply section, which starts near the main power source. The existing system perfectly suits single-phase networks, but its use when grounding electrical equipment operating in a three-phase electrification network is unacceptable.
After the work to protect the equipment is completed, it is required to calculate and check the grounding system. The work involves the use of special devices and equipment, therefore, it should be entrusted only to a qualified specialist. After making measurements, the average resistance of the neutral-phase loop should be determined. Its value should be minimal.
The next step, according to Ohm's physical law, calculates the short-circuit current at the moment the mains phase hits the metal cases of the devices.
The optimal value of the parameter must exceed the response threshold of the automatic de-energizing system. In the opposite situation, they will need to be changed to equipment with lower response threshold values. It is possible to carry out measures to reduce the resistance of the netral-phase loop.
Features of grounding in the apartment
The average consumer should have an idea of what should and should not be done in a living space. The highlights are:
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Limit the use of products grounded through pipes. As a rule, these are washbasins, metal faucets and bathtubs. - With protective grounding of such products, you can get serious injury due to electric current when the basic household appliances are turned on.
- The grounding technique will help to equalize the potentials of the used metal objects in the bathroom, toilet or kitchen.
- In the zone of entry into the apartment, as a rule, there is a device for switching both zero and phase, in the form of a packet or a two-pole device. But you have to be careful. Commutation of the neutral conductor used as a protective conductor is prohibited.
- Every household appliance is required to be zeroed. The problem is irrelevant for residents of new homes. It is solved by bringing the neutral to the sockets. In addition, quality household appliances are equipped with a grounding type plug.
- For old houses, where the wiring is carried out according to the two-wire system, it is possible to carry out grounding using a separate wire from the electrical panel in the apartment.
- It is important to observe maximum safety precautions. Any work must be carried out on a completely de-energized equipment.
In an electrical network, the movement of electrons follows the path of minimum resistance. Without taking protective measures, the current can cause serious harm to a person, it can even be fatal.
Electrical energy in critical situations can ignite flammable substances, which is a direct source of fire. But taking measures to ensure safety (in particular, protective grounding) will help to avoid negative consequences.
