Voltage circuit breaker. Protection against voltage surges and zero loss

Modern home appliances contain sensitive electronics, making these devices vulnerable to power surges. Since it is not possible to eliminate them, reliable protection is necessary. Unfortunately, its organization is not the responsibility of the housing and communal services service, so you have to deal with this issue yourself. Fortunately, purchasing protective devices is not a problem today. Before moving on to the description and principle of operation of such devices, we will briefly talk about the reasons that cause voltage surges and their consequences.

What is voltage drop and its nature?

This term refers to a short-term change in the amplitude of the power supply voltage, followed by restoration close to the original level. As a rule, the duration of such a pulse is calculated in milliseconds. There are several reasons for its occurrence:

Atmospheric phenomena in the form of lightning discharges can cause an overvoltage of several kilovolts, which is not only guaranteed to damage electrical appliances, but can also cause a fire. In this case, it is easier for residents of high-rise buildings, since organizing protection from such predictable phenomena is the responsibility of electricity suppliers. As for private houses (especially with air inlet), their residents should deal with this issue on their own or contact specialists.
Jumps during switching processes when powerful consumers are connected and disconnected.
Electrostatic induction.
Connecting certain equipment (welding, commutator motor, etc.).

The figure below clearly demonstrates the magnitude of the lightning impulse (U gr) and switching impulse (U k) in relation to the rated network voltage (U n).

To complete the picture, mention should be made of long-term increases and decreases in voltage. The cause of the first is an accident on the line, as a result of which the neutral wire breaks, which causes an increase to 380 volts. No devices will be able to normalize the situation; you will have to wait until the accident is resolved.

Long-term voltage drops can often be observed in rural areas or holiday villages. This is due to insufficient power of the transformer at the substation.

What is the danger of fluctuations?

In accordance with acceptable standards, deviations from the nominal value are allowed in the range from -10% to +10%. During surges, the voltage can significantly go beyond the established limits. As a result, power supplies of household appliances are overloaded and may fail or significantly reduce their service life. With high or long-term differences, there is a high probability of ignition of the wiring, and, as a result, a fire.

Low voltage also threatens trouble, especially for refrigeration compressors, as well as many switching power supplies.

Protective devices

There are several types of protective devices that differ in both functionality and cost, some of them provide protection to only one household appliance, others – to all those in the house. We list the well-proven and most common protective devices.

Network filter

The simplest and most affordable option for protecting low-power household equipment. It has proven itself to be excellent at surges up to 400-450 volts. The device is not designed for higher impulses (at best, it will take the blow on itself, saving expensive equipment).

The main protection element of such a device is a varistor (a semiconductor element that changes resistance depending on the applied voltage). It is this that fails when a pulse exceeds 450 V. The second important function of the filter is protection against high-frequency interference (occurring during operation of an electric motor, welding, etc.) that negatively affects electronics. The third element of protection is a fuse that trips during a short circuit.

Filters should not be confused with ordinary extension cords, which do not have protective functions, but are similar in appearance. To distinguish them, just look at the product passport, which contains full characteristics. The absence of such should in itself raise suspicion.

Stabilizer

Unlike the previous type, devices of this class allow you to normalize the voltage in accordance with the nominal one. For example, by setting the limit within 110-250 V, the output of the device will be a stable 220 V. If the voltage goes beyond the permissible limits, the device will turn off the power and resume its supply after the operation of the electrical network is normalized.

In some cases (for example, in rural areas), installing a stabilizer is the only way to increase the voltage to the required standard. Household stabilizers come in two modifications:

Linear. They are designed to connect one or more household appliances.
Trunk, installed at the entrance to the electrical network of a building or apartment.

Both the first and second should be selected based on the load power.

Uninterruptible power supplies

The main difference from the previous type is the ability to continue supplying power to the connected device after the protection has tripped or a complete power outage. The operating time in this mode directly depends on the battery capacity and load power.

In everyday life, these devices are mainly used to connect desktop computers, so as not to lose data in case of problems with the electrical network. When the protection is triggered, the UPS will continue to supply power for a certain time, usually no more than half an hour (depending on the characteristics of the device). This time is enough to save the necessary data and shut down the computer correctly.

Modern UPS models can independently control the operation of the computer via a USB interface, for example, close a text editor (after saving open documents), and then turn off. This is a rather useful function if the user was not nearby when the protection was triggered.

Surge protection devices

All of the devices listed above have a common drawback: they do not have effective protection against high voltage pulses. If this happens, it is almost guaranteed to disable such devices. Therefore, the protection must be organized in such a way that after activation it can be promptly brought into working condition. SPDs meet this requirement perfectly. On their basis, a multi-level system for protecting the internal lines of a private home is organized.

One of the accepted classifications of such devices is shown in the table.

Table 1. SPD classification

Category	Application
B (I)	Provide protection in the event of a direct hit from a lightning discharge through the lightning protection system. Installation location - input distribution device or main distribution board. The main normalizing characteristic is the magnitude of the pulse current.
C (II)	They protect the current distribution network from switching impulses, and also play the role of a second protective level during a lightning discharge. Installation location: distribution board.
D(III)	They provide the last level of protection, in which residual voltage surges and differential overvoltages are not allowed to consumers. In addition, high-frequency interference is filtered. Installation is carried out in front of the consumer. They can be made in the form of a module for a socket, an extension cord, etc.

An example of three-level protection is shown below.

SPD design features.

The device is a platform (C in Fig. 6) with a replaceable module (B), inside of which there are varistors. If they fail, the indicator (A) will change color (in the model shown in the figure to red).

SPD Finder (category II)

Externally, the device resembles a circuit breaker, the mounting is the same (for DIN rail).

A special feature of SPDs is the need to replace modules when varistors fail (which is quite simple). The modules are designed in such a way that it is impossible to install them on a platform with a different rating. The only serious drawback is related to the characteristic features of varistors. They need time to cool down; repeated exposure to lightning strikes significantly complicates this process.

Safety relay

In conclusion, we will consider voltage control relays (VCRs); these devices are capable of protecting household appliances from switching pulses, phase imbalance, and low voltage. They cannot cope with lightning impulses because they are not designed for this. Their scope of application is protecting the internal network of an apartment, that is, where providing lightning protection is the responsibility of electric companies.

The devices can be installed in the input panel, directly after the electric meter, for this purpose a DIN rail mount is provided.

In addition, modifications of devices are produced in the form of power extension cords and modules for sockets.

These devices can only perform a protective shutdown of the network; if the voltage goes beyond the specified limits (set by control buttons), after normalization of the electrical network it is connected. Stabilization and filtration are not performed.

Cautions

You should not trust the protection of your home to home-made structures; in domestic conditions it can be problematic to configure the assembled circuit and test its operation in critical modes.

Without practical experience in organizing lightning protection, you should not try to implement it yourself; it is better to entrust this work to professionals. We recommend that you consider this part of the article as informational.

All manipulations with the electrical panel, devices and wiring must be carried out only when the power supply is turned off.

In this article we will look in detail at how to protect yourself from power surges and surges in the household electrical network.

Voltage surges are especially relevant for old housing stock, where the electrical wiring is already old, in some places completely dilapidated, connections are loose, and the neutral wire often burns out. And this, in turn, leads to the fact that in some apartments the voltage drops below the permissible level, while in others, on the contrary, it increases abruptly and can reach almost 380V.

A sharp increase in voltage leads to the fact that household appliances simply burn out and fail. And reducing the voltage below the permissible level is especially dangerous for household appliances, which include electric motors: refrigerators, air conditioners, washing machines, etc. The reduced voltage leads to an increase in starting currents in electric motors, which can ultimately lead to damage and failure of their windings .

In order to protect electrical wiring and devices connected to it, special devices are used - voltage control relay. They are also called overvoltage relays, as well as maximum and minimum voltage relays, or simply “barriers”.

Let's take a closer look at the operating principle and connection diagrams of these devices using the DigiTOP voltage relay as an example.

I will not go into detail about the technical characteristics; if necessary, you can find it on the Internet. I will briefly note the most important thing.

The relay circuitry measures the effective voltage value and when the upper setting is exceeded, or when the voltage becomes less than the lower setting, the relay opens its power contact, turning off the phase, thereby disconnecting the external power supply from the internal wiring.

The left down arrow button adjusts the lower voltage threshold (default 170V). The right up arrow button adjusts the upper voltage threshold (default 250V).

By pressing both buttons at the same time, you can adjust the delay time when the relay is re-energized when the voltage returns to the operating range.

In single-phase 220V networks, two main schemes for connecting voltage relays are used:

—in the first circuit, the relay contacts directly control the load, i.e. all the current consumed by electrical appliances connected to the home network flows through them;

— in the second scheme, the relay contacts control the contactor winding, and the load is already connected to the network through the power contacts, thereby relieving the contacts and increasing the reliability of its operation.

The circuit with the contactor is discussed in detail in the video at the bottom of this article!!!

We will consider the first scheme.

The voltage relay is installed after the meter, usually in. The phase wire from the external power supply (after the meter) is connected to the terminal 2 power contact of the voltage relay. Further through the power contact from the terminal 3 phase is supplied to the home electrical wiring network. Zero is supplied to the terminal 1 in order to power the circuitry of the relay itself. Those. the zero is not broken, the relay contacts control only the phase wire.

When the input circuit breaker is turned on, power is supplied to the voltage relay. If the voltage value is in the operating range, then after a delay time (set using the buttons on the front panel), the relay contacts close and the phase is supplied to the internal electrical network and it is ready for operation and connecting consumers.

Let's assume that there was a voltage surge and its value exceeded the upper threshold of 250V. The relay monitors this change and, when the upper limit is exceeded, opens its power contact, thereby breaking the phase wire and stopping the supply of power from the external electrical network to the internal network of the apartment or house.

This allows you to protect connected household appliances and other electrical appliances from failure.

When the supply voltage returns to the operating range again, i.e. becomes less than 250V, the voltage control relay, having withstood the set time delay, will again close its power contact and the circuit will return to operating condition.

In a similar way, protection against unacceptable voltage drop occurs.

Since in this circuit for connecting a voltage relay the load is connected directly through its power contact, when choosing a relay it is necessary to choose a model designed for a current greater than the current of the input circuit breaker. This will provide the necessary margin and protect the relay circuitry in the event of switching the maximum load. We do the same for .

Connection diagrams and operating principles of voltage control relays.

I recommend materials

Whatever one may say, our electric companies are not able to provide a stable supply of electricity to the consumer. Something always happens - either there is not enough of it, or a large excess of it leads to breakdowns of home equipment. In general, the golden mean at 220V is extremely rare - this is the cause of all our troubles associated with the failure of household appliances. Only two devices can save you from this scourge - surge protection and a stabilizer. This is what we will be talking about in this article, in which we will look at the principles of installation and use of this electrical equipment.

Surge protection device

This device is not very convenient to use - the principle of its operation is that when power surges occur, it simply de-energizes the room, thus protecting household appliances from burning out. There are two types of such protection devices - global, capable of taking care of the safety of all electrical appliances in the apartment, and local, which is responsible for protecting exclusively one household consumer.

The global surge protection device is installed directly into the apartment electrical panel, which is assembled at - the principle of its connection is quite simple and almost anyone can cope with its installation.

It even looks somewhat reminiscent of an ordinary double circuit breaker, so the principle of its installation is exactly the same. Using terminals on one side, the phase and zero coming from the central machine are connected, and on the other side, the phase and zero going to consumers. In the event of a power surge, the entire apartment remains without electricity.

Some circuit breakers are produced with three connection terminals (for example, “Bars”). In this case, the phase is a through phase (both incoming and outgoing are connected to it), and the zero connected to the third terminal does not go anywhere.

The local surge protector is a little more loyal in this regard - at least when it trips you are not left completely without energy. The fact is that it is connected directly to, and an electrical appliance is connected to it, or rather, to the socket built into its body. In this way, you can protect expensive apartment equipment that works constantly - for example, a refrigerator, gas or electric boiler.

The surge protector has a simple control principle; it is provided by just two buttons and a touch screen located on the device body. As a rule, the left button sets the minimum permissible voltage in the network, and the right button sets the maximum. By pressing two buttons you can immediately adjust the time interval between turning off and turning on the device, after which the device checks the voltage in the network, and if it is within the limits you set, it supplies voltage to consumers again. These limits of permissible voltage should be mentioned here - as a rule, our household appliances are able to operate safely in a network with voltage from 180V to 240V.

Surge Protectors

This method of protecting household consumers from voltage surges is almost ideal - it does not de-energize all wiring, but simply equalizes the voltage to the required parameters, making it stable. The only drawback of this device is its cost. Not everyone can afford to buy a voltage stabilizer.

Due to its size, this complex of protective equipment cannot be installed in a small apartment electrical panel - as a rule, it is installed separately. There are both wall-mounted and floor-mounted voltage stabilizers for the home.

It is connected to the circuit quite simply. The stabilizer housing has four terminals - two incoming and two outgoing. Voltage is supplied to the incoming ones directly from the main circuit breaker, and from the outgoing ones, stabilized voltage is supplied directly to the consumer.

A very important point when choosing a home stabilizer is its correct selection according to the electricity consumed. You will have to calculate the power of all devices working simultaneously and add a small margin of 20%. For example, if the total power consumption of the appliances in your home is 3 kW, then you need a device of appropriate power.

Both types of protection against voltage surges are equipped with a special screen, thanks to which you can control the operation of the devices. Typically, this screen displays the incoming and outgoing voltage. This way you will know not only the current state of affairs in the city's energy system, but also in your home.

Also read on this topic

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Familiar to many users, power surges in the 220V power supply network are very common; they are caused by disruptions in the operation of the transformer substation or overloads in existing power lines. The only way out of this situation is to install a surge protection device in the apartment, ensuring the safe operation of all equipment connected to it (see photo below in the text).

Reliable protection against power surges for all household appliances in the apartment is possible only if the stabilizing devices have sufficient power. Let's try to understand in more detail the types and models of branded units, most often used in domestic conditions and in offices. But first, it is advisable to become familiar with the main types of supply voltage deviations from the norm.

Types of voltage drops

There are several types of voltage drops in the network, classified by their duration and amplitude. In accordance with these characteristics, they are all divided into the following groups:

Short-term bursts of small magnitude associated with transient processes due to the inclusion of power equipment (elevator or pumping stations connected to the same phase) or with strong lightning discharges;
Long-term voltage drops below the permissible PUE level;
Severe excess of the permissible maximum (overvoltage reaching 260-300 Volts) for a long time;
Constant voltage surges of significant amplitude, arising due to a malfunction of station equipment.

Note! All of the above deviations are arranged in increasing order of their danger for equipment connected to a household network.

Due to this classification, various types of equipment (including devices that respond to short-term surges) must be used to protect against voltage surges. This circumstance presupposes a completely different approach to the selection of protective devices used to connect household appliances.

If, during short-term surges in the network, input two-pole circuit breakers are most often triggered, then in a situation with a long-term voltage exceeding values of the order of 300 Volts, very unpleasant things can happen. In this case, complete burnout of expensive equipment that is not protected by a high-quality stabilizing device is possible. The same consequences are observed if a strong lightning discharge hits a building (this phenomenon is especially dangerous in rural areas).

Methods and means of protection

There are several approaches to preventing emergencies that arise due to disruptions in the normal power supply for the home. Such techniques include:

Use of special relays in power circuits that provide control of operating voltage (RKN);
The use of multifunctional surge protection devices (SPM), mounted in the input circuit of the electrical network immediately after the input circuit breaker;
Setting the release for minimum and maximum voltage (RMM);
Power supply of household appliances through standard voltage stabilizers;
Using a powerful “uninterruptible power supply” (UPS) in the apartment.

Let's look at each of the types of protective equipment listed above in more detail.

RKN and UZM

One of the simplest solutions for protecting the electrical network from current surges and overvoltages is to install an RKN type relay with an indicator board or a UZM safety device into it. The essence of the operation of equipment of this class is quite simple and consists of the following:

The electronic module built into the device continuously monitors the voltage entering the circuit and completely turns it off if the value deviates from the nominal value (in either direction);
The system operates even after a complete power loss, and when it reappears, it begins to function again, automatically adjusting the nominal value in a given range of values;
The limits for adjusting the supply voltage parameters are usually set manually.

In addition, voltage relays allow you to set a time delay for turning on the power supply after a power failure in a fairly wide range of values (from 10 seconds to 6 minutes).

Additional Information. For most household devices that are periodically turned on and off (refrigerators and air conditioners, in particular), restarting is carried out with a delay of up to 5 minutes.

Devices of this type are usually mounted in an electrical panel on a special DIN rail with a standard size of 35 millimeters. The advantages of protective devices RKN and UZM include:

Wide range of setting operating voltage values;
Possibility of shutdown in case of overcurrent and short circuit;
High relay response speed (no more than 0.2 sec.).

To this should be added a significant range of output current adjustment (from 25 to 63 Amperes). A sample of these devices is shown in the figure below.

Voltage control relay RMM

The so-called “releases” of supply lines are very similar in principle to the devices already discussed earlier. They also continuously monitor the mains voltage and, in case of extreme deviations in the form of a current surge, instantly turn off the circuit breaker to which the device itself is connected. The device is put back into operation by pressing the “Return” button.

Note! Sometimes this device is manufactured in a common housing with a circuit breaker, that is, it is one whole (a sample device according to the IEK standard is shown in the photo below).

The advantages of RMM type devices include compactness, simplicity of design and quite affordable price. Their only drawback is the absence of an automatic return to the working position.

Voltage stabilizers and uninterruptible power supplies

Stabilizing devices (or simply stabilizers) belong to the category of expensive equipment that provides a high degree of protection of the home network from fluctuations in voltage and current in the load. They are able to guarantee a constant output voltage within specified limits regardless of any changes at the input terminals.

Before purchasing such a unit, first of all, you should decide on the number of consumers simultaneously connected to it, which significantly affects the choice of the brand and power of the stabilizing device. The main advantages of these devices include:

High performance and durability;
Increased accuracy of regulation of network parameters;
Guaranteed constant operating output voltage.

The disadvantages include the high cost of the purchased product and high energy consumption.

When considering UPS-type converters, you must be able to distinguish them from stabilizers based on the presence of built-in batteries. Thanks to this, such devices not only ensure that the voltage is maintained within specified limits, but also guarantee the continuous operation of household consumers connected to them.

Important! The time the voltage is present at the output when it is lost in the network depends on the capacity and quality of charging of the batteries, as well as on the number of loads connected to the UPS.

The cost of these products is also quite high; its specific value depends on the parameters of the device itself and the capacity of the built-in battery. Devices with an uninterruptible power supply function are usually used for very specific devices (a computer, for example, or a TV), where a power loss can lead to loss of information or malfunction of the equipment.

Review of popular models

"ZUBR"

Let's start with such a widespread Ukrainian product as the protective relay of the ZUBR brand, which is in great demand in Russia. This device is guaranteed by the manufacturer for a period of up to 5 years; at the same time, many users speak well of its work.

A relay device with index 25D, for example, is designed for maximum currents of up to 25 Amperes and provides good mains voltage stabilization characteristics (including thermal protection). This model attracts users with a relatively low cost (for Russia it is about 1500-1900 rubles).

"RESANTA"

This product is also quite cheap (up to 700 rubles) and enjoys some popularity among the broad consumer masses. Another advantage is the absence of any manual controls, which in some situations looks like a disadvantage (it all depends on the user’s preferences).

The shortcomings of this system include a wide range of adjustable voltages (from 170 to 265 Volts), which means continued operation of the equipment in conditions that are dangerous for some types of equipment.

Note! Due to the lack of regulatory authorities, it is not possible to change these boundaries.

Let's add to all that has been said the large dimensions of the device and the low speed of protective shutdown (up to 6 seconds). During such a period of time, with strong overvoltages, most devices will definitely burn out. The recovery time of this device is only 2-3 minutes, which is not enough for some types of household equipment (for refrigerators, for example, this figure should be at least 5 minutes).

RN-111A (113)

This model of relay equipment is produced by a well-known and reliable manufacturer (Novatek).

Products of the RN-113 brand have a number of advantages, the main ones of which are given below:

First of all, this is a fairly high speed of 0.2 seconds (compare with the previous model with its 6 seconds);
Further, a large range of adjustment of the voltage limits;
Possibility of independently setting the moment of restart;
The presence of a digital indicator with operating modes and functional parameters displayed on it.

The only drawback of this device is considered to be the low load capacity (only 16-32 Amperes), which is sometimes not enough for suburban consumption facilities.

In this regard, experts advise supplementing the device with a separate contactor and a special circuit breaker that provides protection for its relay part. As a result, the entire combined design can cost the user about 2.5-3.0 thousand rubles (for the RN 113 model, designed for 32 Amperes, the cost of the kit will increase significantly).

UZM-51M

This device is produced by the St. Petersburg company Meander and is considered one of the most reliable and efficient pieces of equipment in this class.

Its advantages include:

Quite a wide range of setting voltage limits (from 160 to 280 Volts);
High performance (response time is only 0.02 seconds);
Maximum load capacity – up to 63 Amps;
Availability of a protective mechanism against surge voltages;
Relatively small in size and no need to supplement the kit with any elements.

Let's add to this the low cost of the product, which can be purchased on the market for about 2 thousand rubles.

In the final part, we note that before making a final decision on the choice of protective equipment, it is advisable to contact a specialist who can assess possible threats and offer the user one or another sample. At the same time, it is important to understand that purchasing, albeit expensive, but quite effective means of protection against power surges and overvoltages is tantamount to a reliable investment of money.

Video

The structural imperfection of electrical networks is the main cause of sudden voltage surges. It is impossible to predict the time of the next drop. The only thing we can do to prevent unpleasant consequences is to protect electrical consumers in our home in advance. In this article we will tell you how and with what to protect the network of your apartment and house.

What will save you from a surge?dressing up

Protection against voltage surges is possible using different types of protective devices. We'll talk about the most common ones. These are voltage control relays (RN) and household stabilizers.

Surge Protection Relay

Protecting your home from power surges using a LV is recommended in cases where the voltage in the network is stable and its noticeable surges are rare. RN is a device capable of reading the parameters of an electric current and breaking the electrical circuit at the moment when the indicators go beyond a given range. After the indicators in the general network are normalized, the device will automatically close the circuit and restore power to consumers. The function of restoring power after a specified period of time (with a delay), built into the 220V voltage relay for the home, helps to extend the life of some household devices, refrigerators, etc.

LVs have small dimensions, relatively low cost and good performance. The disadvantages of RNs include their inability to smooth out fluctuations in electrical energy. For maximum protection of all consumers, you will need to install several devices at once.

The LV protects the network only from unacceptable voltage surges and is not intended to protect against short circuits (this function is performed by circuit breakers).

Modern launch vehicles come in three types:

1. A stationary relay built into the electrical panel of a house or apartment.

2. Relay for individual protection of one consumer.

3. Individual protection relay for several consumers.

If everything is almost clear with the operation of relays of the second and third types, then the first type LV has a more complex design, and its installation requires certain knowledge. Such devices are mounted at the entrance to the premises, thus providing protection against power surges in the network of all household electrical equipment.

Selecting a launch vehicle

When choosing a relay to protect your home network, it is enough to know the rating of the electric current that the input circuit breaker is capable of passing through. If, for example, the switch capacity is 25A (which corresponds to a power consumption of 5.5 kW), then the performance characteristics of the LV should be one step higher - 32A (7 kW). If the switch is designed for 32A, then the relay must withstand a current of 40 - 50A.

loa FORUMHOUSE user

For this case, I took a 40 A relay, with an input circuit breaker of 25/32 (the first one is, but the setting will increase).

Some people choose a PH brand based on total power consumption. This is not entirely correct. After all, a relay capable of withstanding a current of 32A can safely operate both at a load of 7 kW and at a much higher power consumption. Only in the second case, it is necessary to integrate a special magnetic contactor into the working circuit of the LV. But more on that in the next section.

LV installation

The standard diagram for installing a LV in a distribution panel is shown in the figure. This is the simplest protection against power surges.

Work on installing the pH should only be carried out with the main switch turned off!

As you can see, everything is simple: the control relay is installed immediately after the electric meter and is connected to the phase wire through which power is supplied to the entire house. When a surge occurs beyond the set (adjustable) range, the relay disconnects the external power supply from the internal electrical wiring, and protection against voltage surges is provided in the apartment and in the house.

The pH mounted in the panel panel takes up minimal space on the DIN rail.

If the power of home network consumers totals 7 kW or more, manufacturers strongly recommend integrating an additional electromagnetic contactor into the operating circuit of the LV. Although, a reliable contactor in the overall scheme will never become an extra detail, see the following comment:

Vitichek FORUMHOUSE user

It is better to install a contactor to any relay, although manufacturers write that the LV can withstand high currents. The contactor has larger contacts and lower resistance.

This device helps relieve the load on the LV contacts, independently disconnecting the power line from the general network of household consumers. The control relay, at the moment of unacceptable overvoltage, only issues a shutdown command. After this, the electromagnetic coil of the contactor disconnects the power contacts connecting the external and internal networks. The connection diagram in this case will be as follows:

Overvoltage protection system.

Protection against voltage surges 220V

In order for the LV to benefit its owner, its operating parameters (permissible voltage limits and power resumption delay time) must be correctly adjusted. If the operating circuit uses one pH, then the limits of permissible values should be set based on the characteristics of household appliances that are sensitive to changes. The most sensitive and expensive equipment is audio and video equipment. The range of permissible voltage values for it is 200 – 230V.

The permissible voltage deviation from the nominal values in domestic energy networks is 10% (198...242V). In the case of frequent activation of the LV, these indicators can be taken as a basis when adjusting the relay. However, in this case it is recommended to protect sensitive consumer electronics with the help of low-priced portable stabilizers.

DenBak FORUMHOUSE user

Nobody says that you need to turn off at plus or minus 15V. There is a range of maximum permissible deviations of 10%, which most devices should withstand. Based on this, you need to set approximately 190V-250V. Although, with our state of networks, especially in the private sector, everything is expected. So reasonable caution won't hurt.

In order to ensure the most reliable protection for all consumers, an electrical circuit with several relays should be used. A working protection scheme, including several LVs, allows consumers to be divided into groups - in accordance with their sensitivity to overvoltage:

The first group includes audio and video equipment (permissible voltage values - 200 - 230V);
The second includes household appliances equipped with an electric motor: refrigerators, air conditioners, washing machines, etc. (permissible values – 190 – 235V);
The third group is simple heating devices and lighting (permissible values - 170 - 250V).

Each consumer group is connected to its own RN. In this scheme, the operating parameters of each relay are configured individually.

Protecting the network from overvoltage and surges.

The power resumption delay time must comply with the operating requirements for household appliances. For some refrigerators, for example, the recommended delay is 10 minutes.

Three-phase network protection using LV

If the power supply to your home is carried out through a three-phase system, then it is advisable to install a separate control relay for each phase.

Three-phase voltage relays are designed solely to protect the relevant equipment (electric motor, etc.). If such a relay is installed at the entrance to the home, then a voltage imbalance in one of the phases leads to de-energization of all single-phase consumers.

Surge Protectors

If your house experiences constant power surges, the LV will operate several times a day, de-energizing the entire house. Therefore, in such cases, a less simple, more expensive, but also more practical method of protecting home electronics is recommended. It consists of using stabilizers - devices that smooth out voltage surges in the external network, producing a constant 220V output.

Based on the type of connection, there are two types of stabilizers: local (which are connected to an outlet, protecting from one to several consumers) and stationary (connected to the input power cable and protecting all consumers of the home network). Local stabilizers should be used to protect the most sensitive household appliances. They can be used in conjunction with a stationary launch vehicle.
Stationary stabilizers are complex devices that not only smooth out voltage drops throughout the entire household network, but are also capable of saving expensive equipment by automatically turning off the power to consumers when overloaded and reaching critical values.

It is highly recommended to install stationary stabilizers if the voltage value goes beyond 205...235V several times a day (this can be determined using an ordinary tester).

If the lights in the house are constantly blinking, and the voltage goes beyond 195...245V, then using household electrical appliances without a stabilizer is prohibited!

How to choose a stabilizer

The stabilizer should be selected based on the total power of household consumers. The device must have a decent amount of power.