Grounding and zeroing of technical security equipment. Grounding and grounding of electrical installations, types (TN-C,TN-S,TN-C-S,TT,TI), advantages and disadvantages. Protective function of earthing

Zeroing called the electrical connection of metal non-current-carrying parts of electrical installations with grounded neutral secondary winding three-phase step-down transformer or generator, with a grounded source terminal single-phase current, with a grounded midpoint in networks direct current.

The operating principle of grounding is based on the occurrence of a short circuit during phase breakdown to a non-current-carrying part of an instrument or device, which leads to the activation of the protection system ( circuit breaker or blown fuses).

Grounding is the main measure of protection against indirect contact in electrical installations up to 1 kV with a solidly grounded neutral. Since the neutral is grounded, grounding can be considered a specific type of grounding.

In 380/220 V networks, grounding of neutrals (zero points) of transformers or generators is used in accordance with.

Let us first consider a 380 V network with a grounded neutral. Such a network is shown in Fig. 1.

If a person touches the conductor of this network, then under the influence phase voltage a damage chain is formed, which closes through the human body, shoes, floor, ground, neutral grounding (see arrows). The same circuit is formed if a person touches a housing with damaged insulation. However, it is impossible to simply ground the body of the electrical receiver.

Rice. 1. Touching a conductor in a network with a grounded neutral

Rice. 2. Grounding the electrical receiver in a network with a grounded neutral

To understand this, let’s assume that such grounding has been completed (Fig. 2) and a short circuit to the motor housing has occurred in the installation. The short circuit current will flow through two grounding conductors - the electrical receiver Rз and the neutral Ro (see arrows).

Rice. 3. Grounding an electrical receiver in a network with a grounded neutral

For this reason, in installations with a grounded neutral with a voltage of 380/220 V, a different type of grounding system is used: all metal cases and structures are electrically connected to the grounded neutral of the transformer through the neutral wire of the network or a special neutral conductor (Fig. 3). Thanks to this, any short circuit to the housing turns into short circuit, and the emergency section is switched off by a fuse or circuit breaker. This grounding system is called grounding.

Thus, ensuring safety during grounding is achieved by disconnecting the section of the network in which a short circuit to the housing occurred.

The protective effect of grounding consists in automatically disconnecting the section of the circuit with damaged insulation and at the same time reducing the potential of the housing for the time from the moment of closure to the moment of disconnection. After a person touches the body of an electrical receiver that has not switched off for any reason, a current branch will appear in the circuit through the person’s body.

In addition, if an RCD is installed in this line, then it also trips, but not from a large current, but because the current in the phase wire becomes unequal to the current in the neutral working wire, since most of current takes place in the protective grounding circuit past the RCD. If both an RCD and a circuit breaker are installed on this line, then either both of them will work, or one or the other, depending on their speed and the magnitude of the fault current.

Just as not every grounding provides safety, not every grounding is suitable for ensuring safety. Grounding must be carried out so that the short circuit current in the emergency section reaches a value sufficient to melt the fuse link of the nearest fuse or turn off the machine. To do this, the resistance of the short circuit must be sufficiently small.

If the shutdown does not occur, then the short circuit current will flow through the circuit for a long time and in relation to the ground, voltage will arise not only on the damaged case, but also on all grounded cases (since they are electrically connected). This voltage is equal in magnitude to the product of the fault current and the resistance neutral wire network or neutral conductor and can be significant in size and, therefore, dangerous, especially in places where there is no potential equalization. To prevent such a danger, it is necessary to carefully carry out PUE requirements for the zeroing device.

The protective effect of grounding is ensured by reliable operation of the maximum current protection to quickly disconnect a section of the network with damaged insulation. By time automatic shutdown of a damaged line for a 220/380V network should not exceed 0.4 s.

To do this, it is necessary that the short circuit current in the phase-zero circuit meets the condition Ik >k Inom, where k is the reliability coefficient, Inom is the rated current of the setting of the disconnecting device (fuse, automatic ic switch).

The reliability factor k according to the PUE must be no less than: 3 - for fuses or circuit breakers with a thermal release ( thermal relay) For normal premises and 4 - 6 - for explosive premises, 1.4 - for automatic ical switches with electromagnetic release in all rooms.

Spreading resistance of the neutral grounding device Ro ( working grounding) should be no more than 2, 4 and 8 Ohms, respectively, at rated voltages of 660, 380 and 220 V three-phase electrical installations.

A prerequisite for the safe operation of electrical appliances and various equipment is high-quality grounding and grounding. This work is carried out independently, which avoids equipment failure due to overvoltage and short circuits in the network. Grounding and grounding of electrical installations is carried out taking into account the characteristics of the equipment, which will prevent its premature failure.

Definition of concepts

Grounding is usually understood as the use of special structures that connect the electrical wiring of a house or individual devices to the ground. Thanks to the presence of such protection, touching surfaces that are energized will not lead to death, and the electric shock will be minimal. Protection is manufactured with electrical equipment having an insulated neutral. Grounding devices can be made of a whole group of conductors connecting current-carrying elements to the ground.

Grounding electrical equipment also increases emergency short circuit currents, which is necessary in cases where the existing protection is triggered when non-current-carrying parts become energized. This allows you to prevent equipment failure due to short circuits, unqualified repairs and interference in the electrical network. Today it is customary to distinguish several types of grounding:

the working type ensures uninterrupted operation of electrical equipment in normal and emergency modes;
protective type ensures the safety of electrical installations, preventing breakdowns on the housing and work surface live wires;
The lightning protection type diverts lightning from buildings, discharging the discharge into the ground, preventing damage to electrical equipment and fires in buildings.

It is also customary to distinguish between artificially manufactured and natural grounding. The first is carried out to protect structures and electrical appliances from high voltage. Such devices consist of a metal rod, wire, substandard pipes and steel angle devices. Natural grounding also made by man, but it was not originally intended for protection against overvoltage. It can be considered as reinforced concrete structures, pipelines, casing, etc.

Zeroing also provides necessary protection electrical equipment, preventing its failure due to short circuits and overvoltage in the network. This type of work differs from grounding in terms of installation principle and purpose. Grounding involves connecting conductive elements to the body of an electrical device or metal parts. To ensure safety, a connection to the neutral, which is a source of three-phase reduced voltage, is required.

The main task of grounding is to protect electrical equipment and working personnel from electric shock due to the operation of automatic switching equipment. The principle of operation of such protection is to create artificial short circuits when current enters the equipment body or in cases of insulation breakdown. The occurrence of a short circuit triggers:

fuses;
circuit breakers;
special short circuit protection.

Grounding differs from grounding by the use of special equipment that uses a neutral and, due to short circuits, breaks the circuit, preventing serious electric shock. A feature of grounding is the need for high current power in the neutral wire, due to which a short circuit occurs. Only in this case can a 100% probability of protection against electric shock be ensured if there are problems in the power supply. If the power of the neutral wire and the short circuit currents are insufficient, this leads to increased voltage in the electrical equipment.

Technology selection

When planning electrical protection at home, many of us think about implementing additional protection electricity supply However, homeowners do not always understand the difference between grounding and grounding. The main differences are:

when grounding, excess current is diverted into the ground, and when zeroing is performed, the voltage in the panel is reset to zero;
Grounding is considered the most effective way to protect a person from electric shock.

Grounding is easier to do than grounding. In the latter case, you will need the help of a specialist who must calculate optimal performance zero current and only then can the correct operation of the protective equipment be ensured.

Owners of private houses most often resort to grounding, but owners of apartments in high-rise buildings need to do grounding, for which they additionally install RCDs and similar devices that prevent electric shock and damage to operating electrical appliances. At correct device protection can completely eliminate the risk of electric shock, and various techniques and the devices will be completely protected from possible power surges and short circuits in the network.

To ensure high-quality protection during grounding, it is necessary to take into account the phase phase of the devices and carry out complex calculations. It is not possible to carry out such work independently. Only an experienced electrician will correctly plan the connection, install appropriate protective devices and carry out high-quality grounding.

The completed grounding will not depend on the difference in devices, so it is easier to arrange it yourself, even without any professional skills. Dumping excess voltage into the ground is much safer than installing additional devices that divert current to the panel.

Available for sale today ready-made kits for grounding a private house. You only need to bury the metal circuit a few meters into the ground and connect the phase from the panel to it, which will ensure maximum safety for the electrical appliances used. You can select various kits that are suitable for a summer house or a full-size private house, differing in their design, connection method and maximum possible load.

IN last years There is a trend when full zeroing is carried out in production and enterprises where it is necessary to ensure increased electrical safety of operating devices and industrial equipment. Ordinary homeowners, in order to protect against electric shock, install simple grounding, which is not difficult to do yourself.

Types of protective systems

The basic requirements for grounding and grounding are described in GOST, which simplifies the performance of such work and standardizes the devices used. Protective systems differ in the method of arrangement, operating principle and additional equipment used.

The TN-C system was developed in Germany at the beginning of the last century. Such protection involves the use of a single cable with a PE conductor and a neutral wire. The disadvantage of this grounding system is the appearance of excess voltage when the equipment casing is damaged and the zero burns out. Despite its shortcomings, TN-C is popular today due to its ease of implementation.

Systems grounding TN-S and TN-C-S use two wires that extend from the panel and go into the ground. The circuit is made in the form of a complex metal structure, which completely eliminates the possibility of electric shock and failure of electrical appliances in the event of problems with the power supply. This scheme turned out to be extremely successful; it is popular and is being installed in dachas and private homes.

Grounding type TT is based on the connection of the electrical installation circuit with metal elements located underground. This scheme is not widely used today due to the complexity of implementation, as well as possible voltage drops in the network.

A type of OT protection involves transferring excess voltage to the housing and to the ground from the neutral, which is isolated from the ground and connected to devices with high resistance. This scheme has become widespread when using electrical equipment that requires stability and increased safety.

Popular methods of zeroing

PNG nulling is simple in design, which is explained by the combination of protective and neutral conductors. The disadvantages of this safety system include increased requirements for the interaction of the conductor cross-section of its potentials. PNG is widely used when it is necessary to reset asynchronous units operating in three-phase networks.

The most popular today are modified systems for grounding electrical installations, which are powered by single-phase network. They use a common combined PEN conductor connected to a solidly grounded neutral. After this connection, the PE and N cables are separated, which are then connected to the housing or similar protection devices. The advantage of this grounding technology is its versatility, the ability to be used in single-phase and three-phase networks, as well as simplicity of design and complete safety.

Grounding and grounding of electrical installations allows you to protect equipment from power surges and short circuits. Zeroing involves the use of special equipment that allows you to redirect excess voltage to the shield. This type of protection is mainly used for industrial enterprises and facilities where increased safety of equipment operation is required. Owners of private houses can carry out grounding themselves, which will allow them to protect themselves and the electrical appliances they use from short circuits and surges in the network.

One of the main protective measures is grounding, which consists of a deliberate electrical connection between the electrical installation housing and the grounding device. There are two options - grounding and neutralizing electrical installations. Their main function is to protect against the effects of electric current when a person touches the body of the device or its separate parts. As a rule, these parts become live due to insulation failure.

Features of protective grounding

Most often, protective grounding is used. Currently, special ones equipped with grounding contacts are used. The lower its resistance, the higher the efficiency of the grounding device.

When the insulation breaks down, the device body is often energized. If there is grounding, the current will not pose a danger; it will simply go into the ground through the ground electrode, which has low resistance. In addition to the grounding conductor, the grounding device includes grounding conductors.

Grounding electrodes can be natural, consisting of metal structures of buildings and structures connected to the ground. Artificial grounding conductors are made from steel pipes, corners or rods, the length of which must be at least 2.5 m. They are driven into the ground and connected to each other with steel strips or wire.

Thanks to protective earthing, dangerous voltages are significantly reduced. It can be reduced by using large quantity additional artificial grounding conductors.

Application of protective grounding

Unlike grounding, protective grounding consists of the deliberate electrical connection of those parts of electrical installations that are not normally energized. They also have a neutral wire.

When any phase is short-circuited to the installation body, a short circuit occurs between this phase and the neutral wire. The magnitude of the current, in this case, increases significantly compared to conventional protective grounding. Damaged equipment quickly and completely shuts down, which is main goal zeroing.

There are two conductors performing various functions. The role of the neutral working conductor is to power electrical installations. It has the same insulation as other wires; operating current freely passes through its cross-section. The main purpose of the neutral protective conductor is to create a short circuit for a short period. At the same time, a quick shutdown occurs, ensuring.

Thus, grounding and neutralizing electrical installations allows not only to reliably protect them, but also to protect them from electric shock.

The main condition safe operation electrical installations is a choice correct scheme protection against accidental exposure of high potential to metal parts not used for energy transmission (cases, frames, etc.). To solve this problem, the requirements of current standards (PUE, in particular) provide for the use of special protective devices called grounding devices - GD. They are installed in close proximity to the protected structure and have the appearance shown in the figure below.

The process of arranging structures that protect structures and people from electric shock or lightning is commonly called grounding in electrical engineering. In order to have a complete and clear understanding of what such grounding is, you will need to investigate it distinctive features and principles of organization in more detail.

The essence of grounding

Grounding refers to the intentional connection of metal parts of electrical installations and other equipment, in this moment not energized, with elements of special devices called grounding electrodes. The design of the latter usually consists of several steel pins driven into the ground or pieces of reinforcement welded together by strips of the same metal.

Complete with a set of flexible copper wires and thick strips (busbars), the grounding conductors form a so-called “grounding loop” to which the housings of all electrical appliances available at the site and in need of protection are connected. Since the circuit itself is partially or completely immersed in the ground and has almost perfect contact with it, its potential is normal conditions is close to zero, which allows us to draw the following conclusions:

When hit high voltage on metal parts of a protected object or device, its value will immediately decrease to a level safe for humans (photo below);

If a person or animal accidentally touches the housing of emergency, but thus protected equipment, they will practically not suffer from high voltage;
In a situation where a sensitive device is installed in the supply line that responds to third-party leakage currents (RCD, for example), when dangerous voltage appears, it will operate and instantly disconnect this section from the power source.

This is the essence of the grounding effect, which should not be confused with another protection technique often used in electrical engineering, called grounding.

The concept of zeroing

Every user inexperienced in electrical terms may have a question: what is the difference between grounding and grounding, and also when is the latter used?

To understand the difference between grounding and grounding, it is necessary to consider the principle of protecting equipment of distribution substations, the essence of which boils down to the following:

Equipment of any power stations, including the step-down transformers installed on them, has a zero point or neutral;
In accordance with the requirements of the PUE, this point must be connected to a local charger located directly on the territory of the substation;
Grounding is carried out in the form of a direct connection with the ground, as a result of which such a point is called solidly grounded;
The effect of this grounding applies to all consumers connected to this electrical substation through an extensive power supply system.

Thus, up to each consumer, together with phase wires the so-called “zero protective” conductor is supplied, already tightly grounded on the substation side (see photo).

Note! IN modern systems power supply (TN-C-S, for example), it is laid separately from the working bus N with a PE wire.

When grounding the receiving equipment, its metal parts are deliberately connected not to the charger (as is done when grounding), but to the combined neutral wire that is part of the power supply system. IN TN-C-S system they are connected to a separate PE conductor.

Zeroing ensures a reduction in the risk of electric shock when accidentally touching open metal parts equipment that became energized as a result of an accident. When questions like “what is the difference between grounding and grounding” arise, you should always remember that the first guarantees automatic disconnection of the damaged line from the supply network, while the second does not.

Differences between grounding and grounding

Users often wonder whether it is possible to ground instead of grounding, and how this will affect consumer safety. When answering all such questions, one should proceed from the definition given to this type of protection in previous section. It follows from this that functionally zeroing is more effective, since in a short period of time before the station automation is triggered, it performs the same function as a conventional memory.

However, this does not mean that this type protection must be applied always and everywhere. The fact is that zeroing has a number of disadvantages that are a consequence of the peculiarities of its organization. They appear as follows:

The neutral wire of power supply systems is long and is constantly used in active mode (as a conductor through which operating current flows), as a result of which it can collapse over time;

Additional Information. This phenomenon in the technical literature, as well as among specialists, is most often referred to as “zero burnout” (see photo below).

Unlike grounding, the arrangement of which does not depend on the phase of the protected line, when grounding, certain conditions for connecting the protective conductor must be observed;
It is limited in its capabilities, since it can only be used in circuits with a tightly grounded neutral in networks TN-C-S, TN-C, TN-S (if there are N, PE, PEN conductors).

In lines where the connection is organized according to the scheme with isolated neutral(in IT and TT systems), which for their purpose are more suitable for industrial facilities, it will not be able to work.

Also, these two types of intentional protection differ in their scope, namely:

Grounding is usually used in multi-storey residential buildings, where it is almost impossible to organize full grounding;
Re-grounding is more often used in industrial enterprises, where, according to safety regulations, increased requirements are imposed on personnel safety;
This same type of protection is most often used in everyday life (in country houses, in particular), where there are plenty of opportunities for arranging a protective circuit (see photo below).

It should be added that protective grounding and grounding differ in one more important factor. The fact is that in the first case, protection extends only to the area electrical circuit, in which, in emergency mode (during an insulation breakdown), the operating voltage decreased due to current flowing into the ground. At the same time, the rest of the electricity supply system continues to function.

Unlike the grounding effect, when grounded, this section of the power line is completely turned off.

So trying to answer the question of what their difference is will not be entirely correct. It is much more correct to say that grounding and grounding of electrical installations should be used together. Such combined use will provide more effective protection from electric shock.

To summarize their comparison, we note that the principle of zeroing is the transformation emergency situation V single-phase fault, leading to the operation of the station protective automatics. Grounding, on the one hand, represents a reduction in the potential of a dangerous point (reducing the resistance of the ground electrode), and on the other, their equalization.

In this case, it consists in raising the potential of the support with the person standing on it to the voltage level on the grounded body.

Additional items

Both in the case of grounding and grounding, additional conductors must be used to implement protective functions ( copper wires), providing a reliable connection to the memory or zero contact, respectively.

In the first case, this conductor is stretched from the protected point to the grounding contact and is made in the form of a copper braid. In the situation with zeroing the same copper conductor it is laid through hidden places in rooms and other buildings to the distribution cabinet, where its end is fixed on the main grounding bus (GZSh). The neutral working conductor, which is part of the power cable supplying electricity, is also inserted here.

Important! According to the requirements of the organization of grounding (see PUE), the use of one bolt or terminal contact to fasten these two conductors is unacceptable, which is explained by their different operating modes.

At the end of the comparison of two methods of protecting objects from electric shock, the following should be noted. Both of these methods (both grounding and grounding) essentially perform the same function, which is to reduce the dangerous potential to an acceptable level. Whether you lost some point of equipment or protected it with a memory, the effect will be approximately the same.

Video

Which is called electric current, provides a comfortable existence to modern man. Without it, production and construction facilities do not operate, medical devices in hospitals do not operate, there is no comfort in the home, and city and intercity transport is idle. But electricity is a servant of man only when complete control, if the charged electrons can find another path, the consequences will be disastrous. To prevent unpredictable situations, special measures are used, the main thing is to understand what the difference is. Grounding and grounding protect a person from electric shock.

The directional movement of electrons follows the path of least resistance. To avoid the passage of current through the human body, it is offered another direction with the least loss, which provides grounding or grounding. What is the difference between them remains to be seen.

Grounding

Grounding is a single conductor or a group made up of them in contact with the ground. With its help, the voltage supplied to the metal body of the units is reset along the path of zero resistance, i.e. to the ground.

Such electrical grounding and grounding of electrical equipment in industry is also relevant for household appliances with steel external parts. If a person touches the body of the refrigerator or washing machine under voltage will not cause electric shock. For this purpose, special sockets with a grounding contact are used.

Operating principle of RCD

For safe work Industrial and household equipment is used, using devices of automatic differential switches. Their work is based on comparing incoming phase wire electric current and leaving the apartment via the neutral conductor.

The normal operation of the electrical circuit shows same values current in the named areas, the flows are directed in opposite directions. In order for them to continue to balance their actions, ensure balanced operation of the devices, they carry out the installation and installation of grounding and grounding.

A breakdown in any section of the insulation leads to the flow of current directed to the ground through the damaged area, bypassing the working neutral conductor. The RCD shows an imbalance of current, the device automatically turns off the contacts and the voltage disappears in the entire operating circuit.

For each individual operating condition, different settings are provided for turning off the RCD, usually the setting range is from 10 to 300 milliamps. The device operates quickly, the shutdown time is seconds.

Operation of the grounding device

To connect to the housing of household or industrial equipment, a PE conductor is used, which is output from the panel along a separate line with a special output. The design provides a connection between the housing and the ground, which is the purpose of grounding. The difference between grounding and grounding is that at the initial moment when connecting the plug to the socket, the working zero and phase are not switched in the equipment. Interaction disappears in last minute when the contact opens. Thus, the chassis grounding has a reliable and permanent effect.

Two ways of grounding device

Protection and voltage removal systems are divided into:

artificial:
natural.

Artificial groundings are intended directly to protect equipment and people. Their installation requires horizontal and vertical steel metal longitudinal elements (pipes with a diameter of up to 5 cm or angles No. 40 or No. 60 with a length of 2.5 to 5 m are often used). This makes the difference between grounding and grounding. The difference is that a specialist is required to perform high-quality zeroing.

Natural grounding electrodes are used if they are located closest to the object or residential building. Pipelines in the ground made of metal serve as protection. It is impossible to use pipelines with flammable gases, liquids and those pipelines whose outer walls are treated with an anti-corrosion coating for protective purposes.

Natural objects not only serve to protect electrical appliances, but also fulfill their main purpose. The disadvantages of such a connection include access to pipelines for a fairly wide range of people from neighboring services and departments, which creates the risk of violating the integrity of the connection.

Zeroing

In addition to grounding, in some cases grounding is used; you need to distinguish what the difference is. Grounding and grounding remove voltage, they just do it different ways. The second method is electrical connection housing, in in good condition not under voltage, and the output of a single-phase source of electricity, the neutral wire of a generator or transformer, a direct current source at its midpoint. When zeroed, the voltage from the housing is reset to a special distribution panel or transformer box.

Grounding is used in cases of unexpected voltage surges or breakdown of the insulation of the housing of industrial or household appliances. A short circuit occurs, leading to blown fuses and instantaneous automatic shutdown, this is the difference between grounding and neutralizing.

Zeroing principle

Variables three-phase circuits The neutral conductor is used for various purposes. To provide electrical safety with its help, the effect of a short circuit and voltage generated on the housing with phase potential is obtained in critical situations. In this case, a current appears that exceeds the rated value of the circuit breaker and the contact stops.

Zeroing device

The difference between grounding and grounding can be seen in the connection example. Frame separate wire connects to zero on To do this, connect the third core in the socket electric cable with the terminal provided for this purpose in the socket. This method has the disadvantage that automatic shutdown requires a current greater than the specified settings. If in normal mode the disconnecting device ensures operation of the device with a current of 16 Amps, then small current breakdowns continue to flow without shutting down.

After this, it becomes clear what the difference is between grounding and neutralizing. The human body, when exposed to a current of 50 milliamps, may not be able to withstand it and cardiac arrest will occur. Zeroing may not protect against such current indicators, since its function is to create loads sufficient to disconnect the contacts.

Grounding and zeroing, what is the difference?

There are differences between these two methods:

when grounding, excess current and voltage generated on the housing are diverted directly into the ground, and when grounded, they are reset to zero in the panel;
grounding is more effective ways in the matter of protecting people from electric shock;
when using grounding, safety is achieved due to a sharp decrease in voltage, and the use of grounding ensures that the section of the line in which a breakdown occurred on the housing is switched off;
When performing grounding, in order to correctly determine the zero points and choose a protection method, you will need the help of a specialist electrician, and any home craftsman can make grounding, assemble a circuit and deepen it into the ground.

Grounding is a system for removing voltage through a triangle located in the ground from metal profile, welded at the joints. A properly designed circuit gives reliable protection, but all rules must be followed. Depending on the required effect, grounding and grounding of electrical installations are selected. The difference between grounding is that all elements of the device that are not under current in normal mode are connected to the neutral wire. Accidental contact of a phase with zeroed parts of the device leads to a sharp jump in current and shutdown of the equipment.

The resistance of the neutral neutral wire is in any case less than the same value of the circuit in the ground, therefore, when grounding, a short circuit occurs, which is, in principle, impossible when using an earth triangle. After comparing the operation of the two systems, it becomes clear what the difference is. Grounding and grounding differ in the method of protection, since there is a high probability of burning out over time neutral wire, which needs to be constantly monitored. Zeroing is used very often in multi-storey buildings, since it is not always possible to arrange reliable and complete grounding.

Grounding does not depend on the phase phase of the devices, while the grounding device requires certain connection conditions. In most cases, the first method prevails in enterprises where safety requirements require increased safety. But also in everyday life Lately Often a circuit is installed to discharge the excess voltage that occurs directly into the ground; this is a safer method.

Grounding protection directly concerns the electrical circuit; after an insulation breakdown, due to the flow of current into the ground, the voltage is significantly reduced, but the network continues to operate. When zeroed, a section of the line is completely switched off.

Grounding in most cases is used in lines with an insulated neutral in IT and TT systems in three-phase networks with voltages up to 1 thousand volts or above this figure for systems with a neutral in any mode. The use of grounding is recommended for lines with a solidly grounded neutral wire in networks TN-C-S, TN-C, TN-S with available N, PE, PEN conductors, this shows what the difference is. Grounding and grounding, despite their differences, are systems for protecting people and devices.

Useful Electrical Engineering Terms

To understand some of the principles by which protective grounding, grounding and disconnection are performed, you should know the definitions:

A solidly grounded neutral is a neutral wire from a generator or transformer, directly connected to the ground loop.

It can serve as an output from the source alternating current in a single-phase network or the pole point of a DC source in two-phase mains, as well as the average output in three-phase DC networks.

An insulated neutral is the neutral wire of a generator or transformer that is not connected to the ground loop or is in contact with it through a strong resistance field from signaling devices, protective devices, measuring relays and other devices.

Accepted notations on the network

All electrical installations with grounding and neutral conductors present in them must be marked. Designations are applied to tires in the form letter designation PE with alternating transverse or longitudinal identical stripes of green or yellow color. Neutral neutral conductors are marked with the blue letter N, which indicates grounding and grounding. The description for the protective and working zero consists of putting down the letter designation PEN and painting it blue throughout its entire length with green-yellow tips.

Letter designations

The first letters in the explanation of the system indicate the selected nature of the grounding device:

T - connection of the power source directly to ground;
I - all live parts are isolated from the ground.

The second letter serves to describe the conductive parts regarding the connection to earth:

T speaks about the mandatory grounding of all exposed live parts, regardless of the type of connection to the ground;
N - means that protection of exposed parts under current is carried out through a solidly grounded neutral from the power source directly.

The letters separated by a dash from N indicate the nature of this connection and determine the method of arranging the neutral protective and working conductors:

S - PE protection of the neutral and N-working conductors is made by separate wires;
C - one wire is used for the protective and working zero.

Types of protective systems

The classification of systems is the main characteristic according to which protective grounding and grounding are arranged. General technical information is described in the third part of GOST R 50571.2-94. In accordance with it, grounding is carried out according to the IT, TN-C-S, TN-C, TN-S schemes.

The TN-C system was developed in Germany at the beginning of the 20th century. It provides for the combination of a working neutral wire and a PE conductor in one cable. The disadvantage is that when a zero burns out or another connection failure occurs, voltage appears on the equipment housings. Despite this, the system is used in some electrical installations until our time.

The TN-C-S and TN-S systems were developed to replace the unsuccessful scheme grounding TN-C. In the second protection scheme, two types of neutral wires were separated directly from the panel, and the circuit was complex metal structure. This scheme turned out to be successful, since when the neutral wire was disconnected, no linear voltage appeared on the casing of the electrical installation.

The TN-C-S system differs in that the separation neutral wires It is not performed immediately from the transformer, but approximately in the middle of the line. This was not a good solution, since if the zero break occurs before the separation point, then electricity on the body will pose a threat to life.

The connection scheme according to the TT system provides direct connection of live parts with the ground, while all open parts of the electrical installation with the presence of current are connected to the ground circuit through a ground electrode, which does not depend on the neutral wire of the generator or transformer.

The IT system protects the unit, arranges grounding and grounding. What is the difference between this connection and the previous diagram? In this case, the transfer of excess voltage from the housing and open parts occurs to the ground, and the source neutral, isolated from the ground, is grounded using devices with high resistance. This scheme is arranged in a special electrical equipment, in which there should be increased security and stability, for example, in medical institutions.

Types of zeroing systems

The PNG zeroing system is simple in design, it has zero and protective conductors are combined along their entire length. It is for the combined wire that the indicated abbreviation is used. The disadvantages include increased requirements for the coordinated interaction of potentials and conductor cross-section. The system is successfully used for zeroing asynchronous units.

It is not allowed to perform protection according to this scheme in group single-phase and distribution networks. It is prohibited to combine or replace the functions of zero and protective cables in a single-phase DC circuit. They use an additional one marked PUE-7.

There is a more advanced grounding system for electrical installations powered by a single-phase network. It has a combined common conductor PEN connects to the current source. The separation into N and PE conductors occurs at the point where the main line branches into single-phase consumers, for example, in the access panel of an apartment building.

In conclusion, it should be noted that protecting consumers from electric shock and damage to electrical household appliances during voltage surges is the main task of energy supply. The difference between grounding and grounding is explained simply; the concept does not require special knowledge. But in any case, measures to maintain safety household electrical appliances or industrial equipment must be carried out constantly and at the proper level.