Protection of equipment from overvoltage. How to protect household appliances from overvoltage

Breakdowns of electrical household appliances occur quite often, because any electrical unit, when created, is designed to work with a certain level of electricity, i.e. on specific indicators of current strength and voltage in connection networks. Therefore, if these standards are exceeded, an emergency situation may occur.

The use of expensive home appliances, aggressive natural and atmospheric phenomena, and a not too high level of laying power lines make it vital for apartment and house owners to take measures to protect against electrical overvoltage in a private home and minimize possible consequences.

Where does overvoltage come from?

The planning and construction of many high-rise buildings a couple of decades ago was carried out without taking into account today's variety of household electrical equipment: microwaves, multi-compartment refrigerators, high-power irons and other electrically powered devices. Therefore, maximum electricity consumption in the mornings and evenings has a detrimental effect on the operation of the entire electrical network in any home.

Electricity flowing through a cable or wire that is unable to withstand such a load causes it to become abnormally warm during the day and cool during the evening. Due to the laws of physics, the conductor weakens as it becomes wider or narrower. The contacts in the panel on the first floors or in the single input-distribution device in the house noticeably weaken. Also, zero contacts can burn out, which leads to a voltage drop from 110 to 360 volts on all floors, above the floor with burnt out contacts.

Overvoltage in the electrical network can occur as a result of a lightning discharge hitting a power line, substation or elements of a house, and the current strength is simply enormous, about 200 kiloamperes. When lightning enters the lightning rod and then passes along the ground loop, an electromotive force is generated in conductor materials, measured in kilovolts.

Welding work or the simultaneous switching on of electrical appliances by many neighbors or the connection/disconnection of a powerful consumer can also cause a sharp surge in voltage. To protect expensive electrical equipment and the entire private home, network surge protection is necessary.

Features of home electrical wiring protection

Organizing protection against emerging high voltage is one of the key issues when laying an electrical network in a residential building. It is carried out using special transformers and network filters. In many houses, floor panels are installed circuit breakers, which protect against electric currents during short circuits and temporary overloads.

When high loads are possible, all devices that protect networks from overvoltage must have automatic shutdown devices and switches that respond to changes in current levels. As a rule, the most reliable protection against such surges is placed on the input power wire, since it is this that experiences the greatest impact during load peaks.

The surge protection circuit for a home electrical network can be simple or multi-level. Simple - represented mainly by overvoltage relays in floor panels, and multi-stage (combined, protecting both from household power surges and from pulsed ones during thunderstorms) - SPD, i.e. protection devices against surge surges. Such devices are most often found in private homes.

Note! Electronic devices fail due to both increased and decreased voltage in the network (for example, refrigerators are difficult to start, which negatively affects their further operation).

The insulating layers of home electrical networks are designed, as a rule, for standard 220V, therefore, if the voltage increases many times, a spark jumps in the dielectric layer, which can provoke an electric arc and further fire.

To prevent negative consequences, the following protections are used, operating according to the following principles:

• when there is a sharp unscheduled increase in voltage, the electrical circuit in the house or apartment is disconnected;
• outputting the received excess electrical potential from electrical appliances by transferring it to an earth circuit.

If the voltage rises slightly (for example, up to 380 volts), various stabilizers come to the rescue. However, their protective capabilities are quite limited - they are more designed to maintain specified operating values ​​in electrical networks.

When designing protection for a private home, various design solutions and their technical characteristics are considered. It is necessary to take into account the principles of forming a base of surge limiters (SPS). For example, gas-filled arresters, after the pulse has passed, pass through the so-called. accompanying current, the voltage of which is comparable to a short circuit. For this reason, they themselves can be a source of ignition, and they cannot be used for protection against electrical breakdown.

For home networks, varistor protection devices (semiconductor resistors) are most often used - rheostats composed of varistor “tablets” made from a mixture of oxides of zinc, bismuth, cobalt and others. During normal operation of the electrical network, such a circuit breaker allows microscopic leaks, and when a pulse of high voltage passes through, it is capable of instantly switching to the “tunnel” mode and “draining” more than a thousand amperes in a very short period of time, since the resistance on this device decreases with increasing current strength, after which there is a quick return to normal “combat readiness”.

Electrical wiring resistance classes

All electrical appliances in domestic buildings are divided into four main categories, depending on the maximum withstand overvoltage:

• IV category – up to 6 kilovolts;
• III category – up to 4 kilovolts;
• Category II – up to 2.5 kilovolts;
• Category I – up to 1.5 kilovolts.

In accordance with these categories, a protection system is built, which is abbreviated as uzo (device protective shutdown) with surge protection, for marketing purposes they are most often called limiters, but other names are also used. Limiters are mounted in the direction of movement of a possible impulse. So, in the section from the input panel there is a 6-kilovolt pulse, in the first zone it is reduced by an overvoltage limiter to 4 kilovolts, in the next zone it drops to 2.5 kilovolts, and in a residential area using a category III surge protector the pulse potential is reduced to 1. 5 kilovolts. Protection devices of all classes function in a complex, consistently lowering the potential to normal values, which can be easily handled by the insulation of home electrical wiring.

Important! If at least one link of this protective chain malfunctions, an electrical breakdown in the insulation may occur, which will lead to failure of the final electrical device. Therefore, it is necessary to periodically check the serviceability of each element of the residual current devices.

Main devices of the protection system

One of the best ways save the electrical network from power surges - install a stabilizer suitable for technical specifications. These are not cheap devices, and they are not always used, since the voltage in the networks is already quite stable.

Voltage control relays also help eliminate network instability. In the event of a break in the neutral core and a short circuit in sagging cables, such a relay can turn on protective functions even faster than a stabilizer, it only takes 2-3 milliseconds.

Such relays are very compact - they require less space for installation than stabilizers, they are easily installed on a simple DIN rail, the cables are connected simply (unlike the installation of stabilizers, when they are forced to wedge themselves into the electrical network or install a special box for it). Stabilizers hum noticeably, so it is not advisable to install them in residential areas, but relays operate almost silently. In addition, devices that control electrical potential differences consume very little electricity. The price for such relays is several times lower than those for stabilizers.

The operating principle of the control relay is that with a constant supply of electric current, the device determines the potential difference and compares it with permissible values. If the indicators are normal, the keys remain open and current continues to flow through the network. If a powerful impulse passes, the keys are instantly closed and the power supply to consumers is cut off. Such a quick and unambiguous reaction helps to protect all connected household appliances.

Additional Information. Returning to normal mode occurs with a certain delay, controlled by a timer. This is necessary to ensure that large electrical appliances, such as refrigerators, air conditioners and others, turn on in compliance with the rules and technical settings.

The relay is connected via a phase cable, while the neutral cable is included in the internal circuit for power supply.

There are two methods: end-to-end connection (directly) or using a contractor device for communication. It is optimal to connect the relay mechanism before connecting the meter, which will also ensure its protection against overvoltage. However, if there is a seal on the metering device, you will have to install a relay behind it.

Pulse overvoltages in the electrical network of private houses occur due to thunderstorms with lightning or switching surges. For the safety of electrical wiring, special SPD devices are used. As a rule, these are nonlinear surge suppressors (OSN), stabilizers and potential monitoring relays. Of course, setting up such a system is an expensive undertaking, but its cost is much lower than that of expensive electrical household appliances.

Video

Although the supply of electricity to apartments and houses is regulated by law, residents should not fully rely on the relevant services to provide the required quality of electricity. If due to throws mains voltage expensive electrical appliances will fail, and it will be almost impossible to receive compensation. And since problems with power lines are not uncommon, you should take measures yourself to help protect household appliances from breakdown. To do this, you need overvoltage protection, which can be provided by installing an appropriate device in the network - a protective relay, a sensor with an RCD or a voltage stabilizer.

Acceptable electricity parameters

The voltage rating indicated on all household electrical appliances is 220V, however real life This value is not always stable. This is taken into account in the manufacture of modern devices, and they can operate stably with voltage fluctuations from 209 to 231V, as well as withstand a spread from 198 to 242V. If small differences in potential differences were not provided for by the design of household appliances, they would break down constantly. More significant deviations lead to network overload, and this reduces the operational life of the equipment.

To smooth out voltage fluctuations and ensure the safety of devices, it is enough to install a stabilizer. Overvoltage (the so-called sharp jump in potential difference) is much more dangerous for electrical engineering.

Types of overvoltages

Overvoltage can last for either a short or quite a long time. It can be caused by a lightning strike during a thunderstorm or switching caused by a substation problem. To protect against them, an SPD (surge protection device) is connected to a 220 or 380 Volt network (domestic or industrial). Its automatic operation helps to protect the line when exposed to, for example, a powerful lightning discharge, from which a voltage stabilizer cannot save.

Visually about the SPD in the video:

A lightning strike results in the appearance of a powerful electromagnetic pulse, under the influence of which electrical potentials arise in conductors located near the discharge site, and a sharp voltage surge occurs. It lasts only about 0.1 s, but the magnitude of the potential difference is thousands of volts.

It is clear that when such voltage enters home and industrial networks, the consequences can be very serious.

Overvoltage due to switching

This phenomenon can occur when devices that produce a high inductive load are connected to or turned off in the line. These include power supplies, electric motors, and powerful tools powered from the mains.

This effect is due to the laws of commutation. An instantaneous change in the current value in the solenoid, as well as the potential difference across the capacitor, cannot occur. When a circuit with such a load is connected or opened, the appearance of an electric potential caused by self-induction and switching processes is noted at the point of contact.

The transient process is always accompanied by a surge of voltage, which has the opposite polarity to the input. The small capacitance of the conductors in the network causes a resonance that lasts a short time and causes high-frequency oscillations. At the end of the transition process they fade out.

How long the overvoltage will last and what its magnitude will be depends on the following indicators:

• Load inductance.
• Instantaneous value of the potential difference during switching.

• Capacity of connecting electrical cables.
• Reactive power.

Danger of overvoltage

Since the wire insulation is designed for a voltage significantly higher than the nominal value, breakdown most often does not occur. If the electric pulse operates for a short time, then the voltage at the output of power supplies with a stabilizer does not have time to increase to a critical value. The same applies to ordinary light bulbs - if the sharply increased voltage quickly returns to normal, then the spiral does not have time not only to burn out, but even to overheat.

If the insulating layer cannot withstand the increased voltage and its breakdown occurs, then an electric arc appears. In this case, the flow of electrons penetrates through microcracks that have arisen in the insulation and goes through the gases that fill the resulting tiny voids. And the large amount of heat generated by the arc contributes to the expansion of the conductive channel. As a result, the current increases gradually, and the circuit breaker trips with some delay. And although it only takes a few moments, they are quite enough for the electrical wiring to fail.

What devices provide network surge protection?

An electrical line surge protection circuit may include:

• Lightning protection system.
• Voltage regulator.
• Overvoltage sensor (installed together with the RCD).
• Overvoltage relay.

Separately, it is necessary to say about uninterruptible power supplies, through which computers are most often connected in home networks. This device is not intended to provide surge protection. Its function is different: in the event of a sudden power outage, it works like a battery, allowing the user to save information and calmly turn off the PC. Therefore, it should not be confused with a voltage stabilizer.

Operating principle of protective devices

To protect against electrical impulses caused by lightning, a lightning arrester is installed together with an SPD. And you can protect the line from the flow of electrons, the parameters of which do not correspond to the operating characteristics of the network, using special sensors, as well as overvoltage relays.

It should be said that both the DPN and the relay differ in principle of operation and purpose from the stabilizer.

The task of these elements is to stop the supply of electricity if the value of the difference exceeds the maximum threshold specified in the technical data sheet of the protective device or set by the regulator.

After normalizing the parameters of the electrical line, the relay switches on automatically. DPS for line protection should be installed only in conjunction with a residual current device. Its task is to cause a current leak when a malfunction is detected, under the influence of which the RCD will trip.

Visually about the voltage relay in the video:

The disadvantage of this circuit is that it needs to be turned on manually after the voltage returns to normal. In this regard, a voltage stabilizer compares favorably. This device provides an adjustable time delay for current delivery if it is triggered by excessive voltage. The stabilizer is often used to connect air conditioners and refrigeration units.

Long-term overvoltage

Long-term overvoltages very often occur due to a break in the neutral conductor. Uneven load on the phase conductors causes phase imbalance - a displacement of the potential difference towards the conductor with the heaviest load.

In other words, under the influence of an uneven three-phase electric current, voltage begins to accumulate on the neutral cable, which does not have grounding. The situation does not return to normal until a repeated accident completely puts the line out of action or a specialist fixes the problem.

If the neutral wire in the electrical outlet breaks, the voltage will change in accordance with the load, which users who are not aware of the problem will connect to different phases. It is almost impossible to use a faulty circuit, even if a good stabilizer is included in the power line. The fact is that network parameters that regularly go beyond stabilization limits will lead to the device constantly turning off.

You can see clearly about the zero break and what needs to be done about it in the video:

Lack of voltage (sag)

This phenomenon is especially familiar to people living in villages and villages. A dip (sag) is a drop in voltage below the permissible limit.

The danger of sagging is that many household appliances are designed with several power supplies, and a lack of voltage will cause one of them to turn off briefly. The device will react to this by displaying an error on the display and stopping operation.

If we are talking about a heating boiler, and the malfunction occurred in winter time, then the house will be left without heating. Connecting a stabilizer will help avoid this situation. This device, having detected a sag, will increase the voltage value to the nominal value. A stabilizer can save the situation, even if the network voltage drops due to the fault of the transformer substation.

Conclusion

In this article, we explained why network surge protection is needed, what devices provide it, and how to use them correctly. The recommendations given will help readers understand the causes of mains voltage failure, as well as select and install a device to protect the electrical network.

Overvoltage- these are disturbances in the normal operation of the electrical network associated with an increase in the electric field strength to values ​​dangerous for elements of electrical installations and conductive lines. At the moment of overvoltage, an instantaneous impulse or additional voltage wave is superimposed on the rated mains voltage. Such phenomena can cause damage to insulation and cause a fire; they can pose a serious threat to the performance of equipment, and sometimes to the life and health of people. Overvoltages have different natures. However, modern protective equipment makes it possible to neutralize the consequences of all types of network disruptions.

Causes of overvoltages

Depending on the source of occurrence, four types of overvoltages can be distinguished: atmospheric, switching, transient overvoltages of industrial frequency and overvoltages caused by electrostatic discharge.

associated with thunderstorm phenomena. During a thunderstorm, up to 30-100 discharges per second occur in the atmosphere, while each year the earth experiences about 3 billion lightning strikes. In particular, increased attention should be paid to lightning protection of detached houses on the plain. An even greater danger is created by tall trees or structures (masts, pipes) located near the house. High-risk areas also include mountains, wet areas near water bodies, and ferruginous soils.

Lightning often directly strikes transformers, electricity meters and household electrical appliances. It causes overvoltages to occur in all conductive elements. Lightning current causes a thermal effect and melting of insulation at points of impact and this can cause a fire.

The lightning channel, when a strong pulse current passes through it, acts like an antenna, causing overvoltages within a radius of several kilometers. Also, during a thunderstorm, the ground potential increases due to the circulation of lightning current in the ground. Thus, the consequences of thunderstorms are no less dangerous than a direct lightning strike. That is why it is important to provide not only primary protection of buildings (lightning rods), but also to consider secondary protection of internal equipment, in particular power supply and telecommunication networks. This applies not only to private houses, but also to city apartments, which are protected from direct strikes by lightning rods.

Occurs directly in electrical networks, which is why they are sometimes called "internal". They are high-frequency overvoltage waves - from several tens to several hundred kHz. Switching overvoltages can be caused by sudden changes in load on power lines, ferroresonance phenomena and other emergency operating conditions of distribution networks.

The causes of switching overvoltages can also be associated with the operation of equipment on the consumer side. For example, by disabling protection devices ( fuses, switches), turning off or turning on control equipment (relays, contactors), starting or stopping powerful motors. By and large, sources of switching overvoltages can be any device that includes a coil, capacitor or transformer at the power input, including televisions, printers, computers, electric ovens, filters, etc.

Switching overvoltages develop in a repetitive manner and thereby cause premature aging of equipment.

Power frequency transient overvoltages characterized by having the same frequency as the mains (50, 60 or 400 Hz). They arise due to damage to the insulation between the phase and the housing or the phase and the ground (in networks with a grounded neutral), as well as due to a break in the neutral conductor; in this case, single-phase devices receive a voltage of 400 V. Another cause of transient overvoltages is associated with conductor breakdown, for example, when a high voltage cable falls onto a low voltage line. The third reason is the formation of an arc when a high or medium voltage protective spark gap is triggered, causing an increase in the ground potential.

Overvoltage due to electrostatic discharge dangerous mainly for highly sensitive electronic devices. They can occur in dry environments where a strong electrostatic field accumulates. For example, a person walking on a carpet wearing insulating shoes becomes electrically charged to a voltage of several kilovolts. When it touches a conductive structure, an electrical discharge of several amperes is generated with a very short rise time (a few nanoseconds).

Surge protection methods

Primary protection devices overvoltage protection are necessary to prevent direct lightning strikes - they catch and divert its current to the ground. Such devices are located above the level of all other structures, and their height depends on the size of the protected area. As a rule, lightning rods equipped with down conductors are used to protect residential buildings.

Secondary protection devices allow you to ensure normal operation of equipment and networks inside the building under conditions of atmospheric and switching overvoltages. They can be divided into two large groups- devices consistent And parallel protection. The first group includes:

• Transformers that eliminate certain harmonics by appropriately connecting the primary and secondary windings; such protection is not very effective.
• Filters used to limit switching overvoltages in a clearly defined frequency range. Such devices are not suitable for limiting atmospheric surges.
• Surge suppressors consisting of air inductors that limit surges and arresters that drain currents. Most suitable for protecting sensitive electronic equipment, but only protects against surge voltages. They are bulky and expensive devices.
• A surge protector is a reliable device for protecting computers, laptops and electronic equipment from voltage surges - one of the reasons for their failure to operate and the loss of personal data. Provides efficient power supply and suppresses pulsed and high-frequency interference in the electrical network.

Voltage stabilizers serve to normalize networks alternating current and eliminate the problem of voltage fluctuation. In particular, they analyze the input voltage, and then, by switching the windings of their transformer, maintain the required output voltage range.

Uninterruptible power supplies are used to support the operation of equipment in autonomous mode using battery energy in cases of unauthorized shutdown.

Much more popular parallel protection devices, which can be used in installations of any power. It is important to know that the rated voltage of such a device must correspond to the mains voltage at the installation inputs. In the “standby” mode (in the absence of overvoltages), the leakage current should not flow through the protection device, but if an overvoltage occurs that exceeds the permissible value, the device must immediately drain the current caused by the overvoltage to the ground. An important characteristic of such equipment is its speed.

In residential buildings, modular equipment installed in distribution boards is most often used for surge protection. In particular, these are surge protection devices - SPDs and differential load switches with overvoltage protection - RCDs. There are also replacement surge suppressors and surge suppressors available to protect power outlets, providing secondary protection for connected equipment. Some limiters are built directly into devices that consume electricity, but they cannot protect against large overvoltages. To protect telephone and switching networks from overvoltages, low-current arresters are used, which are also installed in distribution boards or built into devices that consume electricity.

Schneider Electric surge protection equipment

The most effective means of providing surge protection in apartments and private houses are modular devices installed in distribution boards. Also, for the purpose of partial protection, network filters can be used.

Differential switches load (RCD) designed primarily to protect people from injury electric shock and preventing fires. However, in the line of modular equipment Easy9, developed by Schneider Electric, also has an RCD that combines protection against current leakage and overvoltage. If a transient voltage of industrial frequency occurs in the network, for example, due to a break in the neutral wire in the entrance of an apartment building, the power will be turned off. Such a device will protect both wiring, equipment, and human life.

Surge protection devices (SPDs) help prevent the consequences of indirect lightning strikes and emergency power surges, which are destructive for expensive electronics; they compensate for strong voltage surges that the RCD is not able to cope with. As a rule, electronics can withstand overvoltages up to 1300-1500 V, while voltage surges during a lightning strike can reach 10,000 V. The task of the SPD is to smooth out surge voltages to an acceptable level of 1000-1300 V.

The most common type of SPD is surge protectors (extension cords with a button), but SPDs are modular (for example, Easy9 from Schneider Electric) provides significantly more reliable and high-quality surge protection. In addition, placing the device in a distribution panel at the entrance to the apartment allows you to protect not only the computer, but also kitchen appliances, climate control equipment, burglar alarm, multimedia systems, charging smartphones, etc. Unfortunately, so far no more than 1% of Russian households are equipped with modular surge protection devices.

When choosing surge protection devices, it is important to take into account the presence of a lightning rod, the organization of the grounding system, and information about short circuit currents.

The presence of an SPD provides complete protection of the power supply system of an apartment or private house and guarantees the safety of all types of expensive household appliances and electronics.

Surge suppressors Acti 9 Designed primarily for industrial and administrative buildings. However, this series also contains equipment that, if necessary, can be used in residential premises for reliable protection against atmospheric surges. These are type 2 surge suppressors with built-in disconnector - iQuick-PF, iQuick-PRD and modular type 2 surge suppressors - iPF & iPRD. Acti 9 equipment provides certified coordination of operation with circuit breakers, in addition, the devices are very easy to install on site, and their condition can be monitored remotely using a monitoring system. For telecommunication networks, iPRC and iPRI protection devices can be used.

In addition, Schneider Electric's product portfolio includes household Surge protection devices APC Surge Arrest Performance. Surge filters of this series are designed to provide the minimum necessary protection of computers, consumer electronic devices and telephone lines from impulse noise.

When choosing a surge protection solution, it is important to consider the cost of the equipment being protected and the consequences of its failure. As well as the risks of overvoltage, which are directly related to the state of the network and lightning activity in a particular area. When thinking about the protection of electrical equipment, it is important not to forget about telecommunication networks, which can also suffer from overvoltages.

Modern life leads to the emergence of everything more complex household appliances, equipment and electronics in our homes and apartments. At the same time, the quality of power supply wants to be better for various reasons. On the other hand, the industry offers a whole range of electrical devices that allow you to solve these problems yourself in your own home. Let's get to know them and make our choice.

Monitoring the voltage level in the network

Types of voltage surges in the power supply network

It is difficult to choose the right surge protection system without knowing its nature and nature. Moreover, they are all natural or man-made in nature:

1. Often the voltage in the network becomes stably low. The reason is an overload of an outdated power transmission line (PTL), for example, as a result of the massive connection of electric heaters or air conditioners in the corresponding season.
2. Under these same conditions, the voltage may be too high for a long time under insufficient load.
3. A situation is possible when, with a stable overall power level, pulses and high voltage surges appear in the power supply line. The reason may be the operation of a welding machine, a powerful power tool, technological equipment or poor-quality contact in power lines.
4. A rather unpleasant surprise is a break in the neutral wire in the 380 V network of the supply substation. As a result of different loads on the three phases, a voltage imbalance occurs, that is, on your line it will be too low or too high.
5. A lightning strike on a power line causes a huge surge in overvoltage, which leads to the failure of both household appliances and internal wiring of buildings, which leads to a fire.

How do plugs and vending machines protect household appliances?

For a long time, in our houses and apartments, fuses called plugs remained a universal means of defense against the troubles listed above. They were replaced by modern circuit breakers (circuit breakers), and reckless people stopped installing bugs, restoring burnt-out plugs. Today, in many apartments, circuit breakers remain practically the only means of protection against problems in the home electrical network.

Circuit breakers are replacing fuses

During operation, a circuit breaker trips when the current flowing through it exceeds the value indicated on its body. This helps protect electrical wiring from overheating, short circuits and fire in case of overload. In this case, the overvoltage manages to damage the electronics, and with a short surge the machine will not even work.

Thus, a powerful impulse caused by a lightning strike passes through the circuit breaker and can puncture the wiring with the listed consequences.

In other words, the machine does not save you from increased voltage and its surges or drops.

Why is a surge protector connected to a home network?

SPDs (surge protection devices) have been developed specifically to organize a protection system against lightning strikes and the resulting overvoltage pulses. Note that power lines have certain means of compensating for lightning strikes. Also in the power supplies of modern electronic devices there are SPDs of class III.

Modular surge protectors for installation in an electrical panel

However, this is not enough if you live in a private house powered by an overhead power line. The method for selecting and connecting an SPD is given in the article. In any case, a lightning rod, which is described in the article “

Functions of an RCD in a house power supply circuit

The power supply circuit of a modern home necessarily contains an RCD - a residual current device. Its main purpose is to protect people from electric shock, as well as to protect electrical wiring from breakdown and leakage, which can lead to a fire. The method for selecting and connecting an RCD is given in a special article.

Single-phase and three-phase RCD

Undoubtedly, if your home has not yet installed an RCD, this must be done. At the same time, the protective shutdown device saves from voltage surges only to some extent and indirectly.

Protecting electrical appliances with a voltage stabilizer

An electrical stabilizer is a device that maintains a stable voltage at the output when it changes at the input within acceptable limits. The device can have different power and provide stable power supply to the entire house or individual consumers.

Voltage stabilizers of various powers

The stabilizer does an excellent job of correcting slowly changing low or high voltages. Depending on the operating principle, it compensates for sudden surges or surges to varying degrees.

Modern units have a function to turn off the power supply when its level in the network reaches limit values. After the input voltage returns to an acceptable value, the power supply is restored.

However, the device does not protect against lightning overvoltage.

Of the devices we reviewed, the stabilizer is the most expensive. Read the article

An alternative option is a network voltage monitoring relay

A budget alternative to a stabilizer is a voltage control relay, which performs the specified function of turning off the power supply when the voltage in the network goes beyond acceptable limits. Depending on the design, the device is triggered when there is an overvoltage, or it also controls its lower level.

Modular voltage relay options

There are relay modifications that restore power automatically when it returns to acceptable limits, or this must be done manually. The most advanced devices provide the ability to set voltage levels at which consumers turn off and the delay time when power returns. For example, a refrigerator should not be plugged in again within five minutes to avoid damaging the compressor. This is the value that can be set on the relay.

The ASV-3M voltage relay must be turned on manually after activation

In this case, the relay does not provide a stable voltage, does not compensate for pulse surges and does not protect against lightning overvoltage. In other words, this method of protection is suitable in a situation where the voltage in the network is normal, but rare and significant deviations are possible, including as a result of an accident in the power supply network.

Voltage relay for low-power consumers

There are options for protecting individual consumers in the form of an extension cord or a monoblock with a plug and socket. These devices are designed for a load current of 6-16A. Similar devices in modular design are mounted on the electrical panel.

A modular type relay can have a switching group of contacts, normally open contacts, as well as two separate groups of normally open or normally closed contacts at the output. This allows you to implement different options for managing consumer power.

Wiring diagram for connecting a voltage relay in a 220V network

The wiring of a modular type voltage relay can be done according to the above illustration. In any case, the device is connected after the input machine. The neutral wire is connected to terminal N, and the phase wires are connected to the normally open contacts of the relay.

To protect a more expensive device, its rated operating current is selected one step higher than the value indicated on the body of the input circuit breaker. For example, if a 40A circuit breaker is installed in front of the relay, choose a device with a rated value of 50A.

If a device with the required operating current is not available or is too expensive, it can be replaced with a voltage relay with a minimum load parameter. In this case, a contactor of the required power or a starter is connected to its output, which supplies voltage to consumers.

Connection diagram for a voltage relay using a contactor

The wiring of the voltage relay paired with a contactor is shown in the diagram. In this example, the voltage relay itself is also connected after the input circuit breaker, meter and RCD. The phase wire from the output contact of the relay is connected to the terminal of the control winding of the contactor, and the neutral wire (the protruding part of the housing) is connected to its second terminal. The power phase and zero are supplied to the output terminals of the contactor (the far part of the housing) from above, and the phase and zero wires of consumers are connected from below.

If there is a normal voltage level in the network, the control relay closes the output contacts and supplies power to the contactor winding. It, in turn, closes the output contacts and supplies power to consumers. If there is no voltage in the network or it goes beyond the permissible limits, the circuits are sequentially broken and the power to the load is turned off.

Connection diagram for several voltage relays in a single-phase network

In some cases, it is convenient to use several voltage relays for different types of consumers. At the same time, for the most expensive electronic consumers, such as computers, you can set the permissible input power range within 200-230V using the appropriate relay.

Household electrical appliances with electric motors, such as a refrigerator or washing machine, can be set to a voltage range of 185-235V. Consumers such as an iron, heater or water heater can be powered by a voltage of 175-245V. The relay's internal timers can be configured to delay power restoration at different times.

How does a phase control relay work in a 380V network?

A three-phase voltage relay can be installed in a 380V network. This makes sense if the house has equipment with three-phase power.

Connecting a voltage relay to a 380V network

In this case, the relay is triggered when there is a voltage deviation in any phase and turns off the load along all three lines. In the absence of consumers with 380V power supply, it is more convenient and cheaper to connect three separate voltage relays. In this case, we get three groups of 220V consumers, for which different voltage limits and delay times can be set.

Connection diagram for a voltage relay on each phase in a 380V network

What does IPB protect against?

The main task of an uninterruptible power supply (UPS) is to provide consumers with electricity when there is no voltage in the network. Most often this device is used to power computers. Although the UPS provides 220 volts for a short time, it is possible to save the information and turn off the computer. It is relevant to use an uninterruptible power supply when using a small-sized power plant for continuous supply of energy at the time of its startup.

Common uninterruptible power supply

Obviously, the use of UPS is functional if a voltage relay is installed in the home's power supply network. When using a battery of sufficient capacity, a gas boiler can be connected to an uninterruptible power supply. A 60Ah battery is enough to supply a 160W boiler with voltage for about a day.

A double conversion UPS operates over a wide range of input voltage variations, but is very expensive.

Probably, in most cases, in for domestic purposes It is more practical to use an inexpensive uninterruptible power supply and a voltage stabilizer or relay at the same time.

How a surge protector can help

Most often, household surge protectors are made in the form of an extension cord. Thus, several units of household appliances can be connected to it at once. Filters differ in the number of sockets and cable length. Typically the device is equipped with its own switch indicating power supply. The filter may have individual power switches for each outlet.

Popular network filters

A number of models have short circuit and overload protection. The total load current of devices of this kind does not exceed 6-16A. The actual filter of such devices consists of several capacitors and inductors. This protects the electronics from low-power and short-duration interference pulses. The latter can be created, among other things, by household appliances connected to the home network.

Overvoltage protection is a power supply feature that shuts down equipment when the voltage exceeds a specified setting. Overvoltages can occur at the source or in distribution networks and last only a few milliseconds, but even such a short-term manifestation of electromagnetic effects on household appliances is destructive, especially for electronic equipment containing semiconductor components.

Causes of emergency situations in the household electrical network

The main factors of overload in the 220 and 380 Volt network:

• thunderstorms and lightning are the highest energy phenomena on Earth;
• improper operation of equipment and low level of qualifications of power grid personnel;
• violation of safety rules during the operation of electrical installations, as a result of which the consumer will not have 220 V, but 380 V or less than 110 V;
• spark static electricity;
• neutral wire break;
• surge voltage due to a thunderstorm hitting a power line;
• current surges in the network due to the simultaneous activation of a large number of devices and equipment.

Consequences of network overvoltage

Exposure to overvoltage conditions can completely damage electrical equipment, cause device malfunctions, lead to fires, and sometimes even explosions. In terms of the number of cases, the second place in the country is occupied by fires caused by overvoltages in the network, when the current instantly increases to hundreds of thousands of amperes, a huge amount of heat is suddenly released in electrical wiring or devices, followed by ignition of their insulation or plastic products.

Voltage surges have a detrimental effect on all household electrical appliances; they can only be protected by using a special surge protection device.

Types of protective devices

To combat network voltage surges, there are many different devices that are easy to install yourself. The products help to most effectively protect your home and loved ones from emergency situations caused by network overvoltage.

There are several types of surge protective devices:

1. Voltage stabilizer - controls the size of the mains voltage.
2. An uninterruptible power supply (UPS) is a device for emergency maintenance of equipment when the main source is turned off, designed on the principle of a backup battery. A UPS is still different from an autonomous power system, as it provides lightning protection by powering the device from battery energy. Time emergency work The UPS is very short (a few minutes), but this is enough to start another source or correct shutdown devices from the network.
3. A circuit breaker is an electrical device with functions similar to that of a fuse. Network overvoltage protection of the simplest circuit breakers is provided by a solenoid, which is activated by an excessive increase in current. Small circuit breakers are widely used instead of fuses to protect electrical systems in homes and apartments.
4. Surge filter is a protective device with built-in electronic circuit protection against pulsed, low- and high-frequency network interference by smoothing it.
5. Nonlinear surge suppressor (SPL) - a device that protects equipment from switching surges and lightning, is the best means of protection.
6. Transformers (step-down and step-up) - change the voltage to operating voltage when there is a regular voltage drop or rise in the network, which is why the devices cannot function at full capacity.
7. Residual current devices (RCDs) are the most common means of protecting people from the danger of electric shock when touching live devices and equipment, as well as protecting against fire caused by leakage currents. Other means of protection cannot perform these functions, since they only respond to network overload.

Sources of impulse noise

Pulse interference (IP) is created by an instantaneous voltage surge in the electrical network with an amplitude of more than 4-6 thousand V. IPs come in the form of a single or multiple (pack) of alternating pulses. This is the most common “disease” of electrical networks and causes irreparable harm electronic components household appliances. IP protection - powering equipment using surge protectors. Other electrical equipment protection systems are practically not configured to protect against IP, and therefore cannot provide it.

There are different sources of IP:

1. Natural springs— lightning strikes close to power grids (aerial or underground), coverage area up to 20 km.
2. Man-made sources - switching processes during the period of operational control of power transmission systems (on/off) and emergency situations at transformer substations.

According to operational data, the most common IP is of a man-made nature, which can be explained by the level of deterioration of networks and the high consumer load.

Equipment safety classes for IP protection

Depending on the pulse power, IP protection equipment is divided into classes:

• lightning protection - 0 (A);
• entrance panel for structure I (B);
• electrical panels for premises - II (C);
• equipment according to GOST-III (D).

Surge protection device (SPD)

There are SPDs - varistors and arresters various designs, usually having indicators indicating shutdown. Varistors have certain disadvantages: after operation they must cool down, which reduces the level of readiness of lightning protection in the event of repeated lightning strikes. They are mounted on a DIN rail, so they are easy to replace if necessary.

Overvoltage protection and reliability of use of the device depends on the efficiency of grounding with equal potentials TN-S or TN-CS, separation of the protective and 0-wires. SPDs are installed with a step of 10 m along the cable, which ensures the calculated sequence of operation of the SPD.

On overhead lines, SPDs are installed from arresters and fuse-links, in the common house panel - varistors CL. I, II, and on the floors - III class. If additional protection is necessary, sockets are equipped in the form of network extension cords.

220 volt surge protection device for home

Overvoltage protection 220 V is a task that you will have to solve yourself: think with your head and collect protection with my own hands. Modern household and Computer Engineering operates safely from 190 to 240 V. A voltage surge creates devastating consequences for equipment when the voltage instantly increases significantly and drops sharply.

The most common causes of overvoltage:

• simultaneous switching off/on of a large number of devices;
• 0-wire damage;
• lightning strikes power lines;
• wire breakage by an external object;
• violation of the wiring diagram in the switchboard.

The industry produces a large list of devices that can reliably provide protection from overvoltage of a 220 V network, and household appliances from damage and high network parameters:

1. VKN (voltage control relays) are installed when voltage drops are a rare phenomenon. RKN - a device that turns off the electrical circuit when the potential difference changes and turns it on when the network parameters are normalized, must have own power exceeding the total power of the connected equipment.
2. DPV (voltage drop sensor) is triggered when the potential difference changes. The DPN causes a current leak, which is detected by another machine - the RCD, which also turns off the network.

Surge Protectors

For normal operation of electrical equipment, the voltage must be maintained in the range from 190 V to 240 V. Protection against surge voltages occurs when permissible parameters are exceeded, for example caused by welding work, carried out near the house, or the appearance of short circuit current in the general house electrical network. In this case, the stabilizer instantly turns off the electricity. After stabilizing the network, the protective device independently supplies voltage to the consumer’s devices.

Network filters

If the filter cannot cope with the interference, it turns off the power with a built-in fuse. Surge protection is used for household multi-level computer networks. A surge protector circuit provides one of the simplest, cheapest, and most effective methods of surge protection. This usually involves a regulated output and a protected circuit or load. SFs operating on the basis of a transistor control the output current and voltage. The protection device shuts down the equipment when the voltage exceeds a preset value.

Surge protection using arresters

Lightning, quasi-stationary and switching overvoltages affect the performance of electrical equipment. The main protective devices are RV (valve arresters) and surge arresters (non-linear surge arresters). The reliability of their operation depends on:

• Selecting the number of devices, their parameters and location.
• Internal surge protection of the arrester itself, which is not protected from this type of impact.
• Tested under normal conditions, they should not break through.

Surge arresters (varistors) consist of a resistor and a spark gap connected in series. This connection scheme changes characteristics in a humid environment, so they are hermetically sealed. This type of arrester operates silently and does not emit gas or flame.

The phenomenon of overvoltage in our networks is not uncommon; power supply systems are outdated, as they are not designed for the modern increased standard of living of consumers. Inflated electricity consumption loads are destroying worn-out networks, causing power surges to occur more and more frequently.

To summarize, it should be said that surge protection methods are, of course, designed to protect against damage high voltage equipment and people, but do not provide a 100% guarantee. During thunderstorms and switching phenomena in the network, the best protection is always to completely disconnect expensive equipment from the power grid.