Grounding and zeroing - what's the difference? Earthing and zeroing of electrical equipment

The directional motion of charged particles, called the electric current, provides a comfortable existence for the modern person. Without it, production and construction facilities are not working, medical devices in hospitals, there is no coziness in the housing, idle urban and intercity transport. But electricity is a servant of man only in the case of complete control, but if charged electrons can find another way, the consequences will be deplorable. To prevent unpredictable situations, special measures are applied, the main thing is to understand what is the difference. Grounding and zeroing protect the person from electric shock.

Directional motion of electrons is carried out along the path of least resistance. To avoid the passage of current through the human body, he is offered another direction with the least loss, which provides grounding or zeroing. What is the difference between them, is to be understood.

Earthing

Grounding is one conductor or a group composed of them, in contact with the ground. With its help, the voltage supplied to the metal casing of the units is reset along the path of zero resistance, i.e. To the earth.

Such electrical grounding and zeroing of electrical equipment in the industry is also relevant for household appliances with steel exterior parts. The touch of a person to the body of a refrigerator or a washing machine that is under stress will not cause an electric shock. For this purpose, special sockets with a grounding contact are used.

Principle of operation of the RCD

For safe operation of industrial and household equipment , protective residual current devices (RCDs) are used, and automatic differential switches are used. Their work is based on a comparison of the incoming electric current flowing through the phase conductor and leaving the flat through the zero conductor.

The normal operating mode of the electrical circuit shows the same current values in the named sections, the flows are directed in opposite directions. To ensure that they continue to balance their actions, ensure balanced operation of devices, perform the installation and installation of grounding and zeroing.

Breakdown in any part of the insulation leads to a current flowing to the ground through the damaged location with the bypass of the working zero conductor. In the RCD, the current imbalance is displayed, the device automatically turns off the contacts and the voltage disappears in the entire working circuit.

For each individual operating condition, various settings are provided to disconnect the RCD, normally the setting range is 10 to 300 milliamps. The device is triggered quickly, the shutdown time is seconds.

Grounding device operation

To connect the grounding device to the housing of domestic or industrial equipment, a PE conductor is used, which is removed from the shield by a separate line with a special output. The design provides the connection of the housing to the ground, which is the purpose of grounding. The difference between grounding and zeroing is that at the initial moment when the plug is connected to the outlet, the working zero and phase are not switched in the equipment. The interaction disappears at the last minute, when the contact opens. Thus, the grounding of the housing has a reliable and permanent effect.

Two ways of earthing device

The protection and tapping systems are divided into:

• Artificial:
• Natural.

Artificial grounding is designed directly to protect equipment and people. For their installation, horizontal and vertical steel metal longitudinal elements are required (pipes with a diameter of up to 5 cm or corners No. 40 or No. 60 with a length of 2.5 to 5 m are often used). Thus, the grounding and grounding are different. The difference is that a specialist is required to perform a quality zeroing.

Natural earthing switches are used in the case of their proximity to an object or apartment house. As a protection are located in the ground pipelines made of metal. Do not use for the protective purpose of the highway with combustible gases, liquids and those pipelines, the outer walls of which are treated with an anticorrosive coating.

Natural objects serve not only to protect electrical appliances, but also fulfill their basic purpose. The disadvantages of this connection include access to pipelines of a sufficiently wide range of persons from neighboring services and departments, which creates the danger of disruption of the integrity of the connection.

Zeroing

In addition to grounding, in some cases using zeroing, you need to distinguish between the differences. Grounding and zeroing drain voltage, only do it in many ways. The second method is the electrical connection of the enclosure, in a normal state not under voltage, and the output of a single-phase electricity source, the zero conductor of the generator or the transformer, a source of direct current at its midpoint. At zeroing, the voltage from the housing is discharged to a special switchboard or transformer box.

Zeroing is used in cases of unexpected voltage surges or breakdown of the housing insulation of industrial or household appliances. A short circuit occurs leading to a fuse blowout and instantaneous automatic shutdown, this is the difference between grounding and zeroing.

Principle of zeroing

Variable three-phase circuits use zero conductor for various purposes. To ensure electrical safety with its help, the effect of a short circuit and the voltage generated on the housing with a phase potential in critical situations is obtained. In this case, a current appears higher than the rated value of the circuit-breaker and the contact stops.

The device of zeroing

What is the difference between grounding and zeroing can be seen in the example of connection. The housing is connected to a separate wire by a separate wire on the distribution board. To do this, connect the third conductor of the electrical cable to the outlet with the provided terminal in the socket. This method has a drawback, which is that for automatic shutdown, a current larger than the specified settings is needed. If in normal mode the shutdown device provides operation of the device with a current strength of 16 Ampere, small current breaks continue to flow without shutting down.

After this, it becomes clear what is the difference between grounding and zeroing. The human body under the influence of a current strength of 50 milliamperes can not withstand and the stop of the heart will come. Zeroing from such current indicators can not protect, since its function is to create loads sufficient to disconnect contacts.

Grounding and zeroing, what's the difference?

There are differences between these two ways:

• When grounded, excess current and the voltage generated on the housing are diverted directly to the ground, and when reset, they are reset to zero in the shield;
• Grounding is a more effective way of protecting a person from electric shock;
• When grounding is used, safety is obtained by abruptly decreasing the voltage, and applying zeroing ensures that the section of the line in which the breakdown to the housing happens is turned off;
• When performing zeroing, to properly determine the zero points and choose the method of protection you will need the help of a specialist electrician, and make a grounding, collect the contour and deepen it into the ground can any home master craftsman.

Grounding is a system for removing voltage through a triangle in the ground from a metal profile welded at the junction points. Correctly arranged contour provides reliable protection, but all rules must be observed. Depending on the required effect, earthing and zeroing of electrical installations are selected. The difference between zeroing is that all the elements of the device, which are not under current in normal mode, are connected to the zero wire. Accidental contact of the phase with the zeroed parts of the device leads to a sharp current jump and equipment shutdown.

The resistance of the neutral neutral wire is in any case less than the same value of the contour in the ground, so when there is a short circuit there is a short circuit, which in principle is impossible when using an earth triangle. After comparing the performance of the two systems, it becomes clear what the difference is. Grounding and zeroing differ in the way of protection, since the probability of the neutral wire fading off over time is important, and it is necessary to constantly monitor it. Zoning is often used in multi-storey buildings, as it is not always possible to arrange a reliable and complete grounding.

Grounding does not depend on the phasing of the devices, whereas for the zeroing device certain connection conditions are necessary. In most cases, the first method prevails at enterprises where increased safety is provided for safety requirements. But also in the home recently, a contour is often arranged for the discharge of the arising excessive stress directly into the ground, this is a safer method.

Protection for grounding concerns directly the electrical circuit, after the breakdown of insulation due to the flow of current to the ground, the voltage is significantly reduced, but the network continues to operate. At zeroing, the line segment is completely disconnected.

Grounding in most cases is used in lines with an isolated isolated neutral in IT and TT systems in three-phase networks with a voltage of up to 1,000 volts or more than this for systems with neutral in any mode. The use of zeroing is recommended for lines with grounded neutral wire in TN-CS, TN-C, TN-S networks with N, PE, PEN conductors available, this shows the difference. Grounding and zeroing, despite the differences, are human and instrument protection systems.

Useful terms of electrical engineering

To understand some of the principles by which protective zeroing is performed, grounding and disconnection should be known:

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

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

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

Accepted designations of grounding devices in the network

All electrical installations with ground conductors and zero wires present in them must be labeled without fail. The designations are applied to the tires in the form of a letter designation PE with variably alternating transverse or longitudinal identical strips of green or yellow. Neutral zero conductors are marked with a blue letter N, so earthing and zeroing are indicated. Description for the defensive and working zero is to put the letter designation PEN and coloring in a blue tone along the entire length with green-yellow tips.

Letter notation

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

• T - connection of the power supply directly to the ground;
• I - all live parts are insulated from the ground.

The second letter serves to describe the conductive parts relative to the connection to the ground:

• T indicates the mandatory grounding of all exposed parts under voltage, regardless of the type of connection with the ground;
• N - indicates that the protection of the open parts under the current is carried out through the neutral grounded neutral from the power supply directly.

The letters, standing through a dash of N, report on the nature of this connection, determine the method of arranging the zero protective and working conductors:

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

Types of protective systems

Classification of systems is the main characteristic by which protective grounding and zeroing 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 schemes IT, TN-CS, TN-C, TN-S.

The TN-C system was developed in Germany in the early 20th century. It provides for the unification of a working neutral wire and a PE conductor in one cable. The disadvantage is that when zeroing out or a different connection violation occurs on the equipment housings, the voltage appears. Despite this, the system is used in some electrical installations to our time.

TN-CS and TN-S systems are designed to replace the unsuccessful TN-C grounding scheme. In the second protection scheme, two kinds of zero wires were separated directly from the shield, and the contour was a complex metal structure. This circuit turned out to be successful, because when the neutral wire was disconnected, there was no linear voltage on the casing of the electrical installation.

The TN-CS system is distinguished by the fact that the separation of the zero wires is not performed immediately from the transformer, but approximately at the middle of the trunk. This was not a good decision, since if a zero break occurs before the point of separation, then the electric current on the housing will pose a threat to life.

The connection scheme for the TT system provides direct connection of the live parts to the ground, with all open parts of the electrical installation with the presence of current connected to the ground loop through the earthing switch, which is independent of the neutral wire of the generator or transformer.

On the IT system, the unit is protected, grounding and zeroing are carried out. What is the difference between this connection and the previous circuit? In this case, the transfer of excessive voltage from the housing and exposed parts occurs to the ground, and the source neutral isolated from the ground is grounded by means of devices with a high resistance. This scheme is arranged in a special electrical equipment, in which there should be increased safety and stability, for example, in medical institutions.

Types of systems of zeroing

The PNG nulling system is simple in design, in which the zero and protective conductors are combined over the entire length. It is for a combined wire that the abbreviation is used. The disadvantages include increased requirements for a well-coordinated interaction of potentials and conductor cross-sections. The system has been successfully used to neutralize three-phase networks of asynchronous aggregates.

It is not permitted to perform protection in this way in group single-phase and distribution networks. It is forbidden to combine and replace the functions of the zero and protective cables in a single-phase DC circuit. They use an additional zero wire marked with the PUE-7.

There is a more perfect system of zeroing for electrical installations that are powered by a single-phase network. In it, the combined common conductor PEN is connected to a deadly neutral in the current source. Separation into N and PE conductors takes place at the point of branching of the main line to single-phase consumers, for example, in the driveway of a multi-unit dwelling.

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