Impulse voltage limiters (SPE). Oin1 Surge voltage limiter wiring diagram

Impulse voltage limiters (OIN) OIN1, OIN2

OIN1, OIN2

PMEA 656111.011 TU Designed to protect electrical equipment and household appliances from lightning and impulse overvoltages. ОИН1 - without operating status indicator; ОИН2 - with an operating status indicator.

Regulatory support

• They meet the requirements of TR CU 004/2011 "On the safety of low-voltage equipment", other standards and PUE ".
• Meets the requirements for overvoltage protection in accordance with GOST R 50571.19

Functionality

ОИН1 - surge voltage limiter monoblock with varistor; on request light indicator of mains voltage presence. OIN2 - surge voltage limiter monoblock with varistor, light indicator of operating status, light indication of mains voltage.

Design features

Impulse voltage limiter (SPE) provides:

• Maximum continuous operating voltage 275 V with a frequency of 50 Hz
• Operating current consumption at a voltage of 275 V does not exceed 0.7 mA
• Made as a unified 17.5 mm wide module for mounting on a 35/7 mm rail
• Withstands combined wave pulses with an open circuit voltage of 10.0 kV and a short circuit current of 5 kA
• Provides equipment protection against impulse overvoltage category II in accordance with GOST R 50571.19-2000 (protection voltage level 2.0 kV)
• Withstands the effects of temporary overvoltage 380 V without damage
• Thermal protection classification: ОИН1 and ОИН2 - without thermal protection.
• Classification by the presence of a status indicator: SPE1 - without indicator; OIN1S (optional) - with a light indicator of the presence of mains voltage; OIN2 - with a light indicator of the operating status.
• Maintainability classification: ОИН1 and ОИН2 - monoblock (not repairable under operating conditions).
• Allows connection of conductors with a cross section from 4 to 16 mm

www.energomera.ru

Surge protection device

Content:

Among the many protective devices, such a high-voltage device as a surge arrester is widely known. Surge voltage surges arise as a result of disturbances in atmospheric or switching processes and can cause serious damage to electrical equipment.

The main means of protecting a house in the event of a lightning strike is a lightning rod or a lightning rod. But he is not able to cope with the discharge that has penetrated the network through the overhead lines. Therefore, the conductor that has taken on this impulse becomes the main reason for the failure of electrical equipment and home equipment connected to this network. To avoid such troubles, it is recommended to turn them off completely during a thunderstorm. Guaranteed protection is ensured by installing surge arresters (SPDs).

Benefits in using arresters

In conventional protective equipment, carborundum resistors are installed, as well as spark gaps connected in series. In contrast to them, non-linear resistors are installed in the arrester, the basis of which is zinc oxide. They are combined into a common column, housed in a porcelain or polymer case. Thus, their effective protection from external influences and safe operation of the device are ensured.

The design features of zinc oxide resistors allow surge arresters to perform broader functions. They freely withstand, regardless of time, the constant voltage of the electrical network. The dimensions and weight of the arrester are significantly lower than that of standard valve arresters.

Arrester specifications

The main value that characterizes the operation of an arrester overvoltage arrester is the maximum effect of the operating voltage that can be supplied to the terminals of the device without any time restrictions.

The current passing through the protective device under the influence of voltage is called the conduction current. Its value is measured in real-life conditions, and the main indicators are activity and capacity. The total value of this current can be up to several hundred microamperes. This parameter is used to evaluate the performance of the arrester.

All surge suppressors are capable of stably withstanding slowly varying voltages. That is, they should not collapse within a certain time at an increased voltage level. The values ​​obtained during the tests allow you to configure the protective shutdown of the device after a specified period.

The value of the limiting discharge current is the maximum value of the lightning discharge. With its help, the ultimate strength of the impulse limiter is established in the event of a direct lightning strike.

The standard service life of the surge arrester is also determined by the current carrying capacity. It is designed to operate under the most severe conditions when maximum lightning or switching overvoltages are present.

Surge protection device

Electrical manufacturers use technology and design solutions that are used in other wiring products. First of all, this is the body material and overall dimensions, appearance and other parameters. Separately, technical issues related to the installation of an arrester and its connection to general electrical installations of consumers are resolved.

There are separate requirements for this particular class of devices. The housing of the surge arrester must provide protection against direct contact. The risk of fire of the protective device due to overloads is completely eliminated. If it fails, there should be no short circuits on the line.

The modern surge arrester is equipped with a simple and reliable indication. A remote alarm can be connected to it.

Surge protection

electric-220.ru

How to organize network overvoltage protection in a private house: circuits, devices, equipment

The presence of expensive electrical and electronic equipment in the house, natural disasters and the poor quality of electricity supply in urban networks force homeowners to take measures to minimize possible damage from the above factors.

This article will focus on practical measures for overvoltage protection that can be implemented when organizing the power supply of a private house. Moreover, these works can be performed both in new construction and in the modernization of existing power supply systems of a private house.

I performed the indicated work when transferring the power supply of the house from a single-phase to a three-phase circuit. Moreover, the work was not only carried out, but also accepted by representatives of the city power grids without comment, and the correct functioning of the devices and the effectiveness of overvoltage protection were tested in practice during operation. It is known that the main condition for connecting to city power grids is the fulfillment of technical conditions (TU), which are issued to the owner of the home. As personal experience has shown, it is possible with a certain skepticism to hope that all measures for the safe operation of electrical equipment will be reflected in the TU data. The photo below shows the technical specifications issued to me in the city power grids.

Note: the items marked in red in the photo were implemented by me on my own even before I received those. conditions. The item marked in blue is more due to the interests of the gorseti themselves (to protect themselves from liability for damage to the owner of the house due to possible problems in their area of ​​responsibility).

Therefore, when developing a draft power supply scheme for a private house, it was decided to use additional measures to protect electrical equipment, which were not reflected in the TU. The photo below shows a fragment of the power supply project for my apartment building.

As can be seen from the photo, in the accounting and distribution cabinet (SCHR1) installed inside the house, a surge protection device (SPD-II) is provided in accordance with the requirements of the TU issued by the city electric networks.

Since the input into the house is carried out via an overhead line, taking into account the requirements of the PUE (rules for electrical installations), surge arresters must be installed at the input to the house, which I took into account in the project (SPD-I in the photo), which are installed in the cabinet ( SCHV1) on the facade of the building. To protect individual electrical consumers in the house, UPS (uninterruptible power supplies) and voltage stabilizers are used.

Thus, overvoltage protection of electrical equipment at home is implemented in three zones (levels):

• at the entrance to the house
• inside the house, in a control cabinet
• individual protection of electrical appliances inside the house

What is important to consider when performing work

First of all, I should note the specific features presented to the performance of electrical work by representatives of city power grids. For example, from the point of view of accounting for consumed electricity, it is enough to verify and seal the electricity meter. But since in each of us they see "potential plunderers of electricity", everything related to the installation of equipment, connections on the site from the city support and up to the meter, inclusive, should be "inaccessible to the consumer", closed (in boxes, cabinets) and sealed ... Moreover, even if these "requirements" contradict the requirements of the technical documentation for the installed equipment, they create the risk of equipment failures, etc. More details about these "specific requirements" will be discussed below.

Now about the technical side of the question:

To protect the electrical equipment installed in the house, I used the following devices and apparatus.

1. As an SPD (surge protection device) - I level I used nonlinear surge arresters (SPD), Russian-made (St. Petersburg), in the amount of three pieces (one for each phase conductor). The factory designation of these devices is OPNd-0.38. They are installed in a sealed plastic box in a steel cabinet on the facade of the house.

What is important to note about this equipment:

• These devices protect only against impulse (short-term) overvoltages arising from thunderstorms, as well as against short-term switching overvoltages, and in both directions. With prolonged overvoltages caused by accidents and malfunctions in the city power grid, these devices will not protect the house.
• Technically, an arrester is a varistor (non-linear resistor). The device is connected in parallel with the load between the phase and neutral conductors. When voltage surges (pulses) appear, the internal resistance of the device instantly decreases, while the current through the device increases sharply and many times, going into the ground. Thus, there is a smoothing (reduction) of the amplitude of the impulse voltage. In connection with the above, when installing these devices, you need to pay special attention to the arrangement of the ground loop and reliable connection of the surge arrester to it.
• Depending on the power supply scheme of the house, the number of surge arresters used may vary. For example, for a single-phase air input, it is enough to install one such device, when powered from a city network via a two-wire line. For a three-phase air input, in most cases, it is sufficient to install three devices (according to the number of phases). If the entry into the house is carried out according to a three-phase, but five-wire scheme, or the devices are placed on the site after separating the common conductor into a neutral working (N) conductor and a protective conductor (PE), then an additional device will need to be installed between the neutral and protective conductors.

2. As an SPD of level II, I used Russian-made UZM-50 M devices (multifunctional protective device).

Of the features of these devices, the following can be noted:

• Unlike surge arresters, these devices provide protection not only against impulse overvoltages, but also protection against prolonged (emergency) overvoltages and dips (unacceptable voltage drop).
• Structurally, they are voltage control relays, supplemented by a powerful relay and a varistor enclosed in one housing.
• For a single-phase network, one device must be installed, for a three-phase network, three devices are required, regardless of the number of supply line conductors.

3. The third important point concerning the correct installation and operation of SPDs when they are switched on in series (shown in the photo by the red rectangles of SPD-1 and SPD-2) is that the distance between them (along the cable length) must be at least 10 meters. In my case, it is equal to 20 meters.

Note: it was impossible to purchase the specified equipment (surge arrester and UZM) in my city, due to its absence on sale, I ordered it via the Internet. This alignment inspired the idea that practically no one pays attention to the issue of protecting electrical equipment, at least in our city.

Practical execution of works

The practical implementation of the work is not very difficult and is shown in the photo below, with small explanations.

Installation of OPN-0.38 at the entrance to the house

The photo shows the installation of a surge arrester in a plastic box. Of the features, it should be taken into account that there are no special boxes for surge arresters, because they are structurally attached to the supporting structure and, according to the type of their design, can be installed openly. Installation of a surge arrester in a box is a forced measure. The box must be able to be sealed. To install the surge arrester in the box, a home-made structure was made of galvanized steel 1 mm thick, which was fixed instead of the standard din rail installed in the box at the factory.

When installing surge arresters and connecting wires to them, the use of engraving washers is mandatory. According to the TU requirements, the introductory machine must be installed in the box with the possibility of sealing. A similar box was used as for a surge arrester, as shown in the photo below (upper plastic box in a metal cabinet).

Such a pile-up of structures (plastic boxes in a metal cabinet) on the facade of the house is due, as I noted earlier, precisely to the specific requirements of city power grids and causes not only a noticeable increase in the cost of work, but also additional costs of effort, time and nerves. In my opinion, technically correct execution of work with air inlet, performed with a self-supporting insulated wire wire, should be as follows: from the support of the power supply networks to the facade of the house, we lay the self-supporting insulated wire wire, attach it to the facade of the house and cut it off with a slight overlap. Then, on each wire of the self-supporting insulated wire, we attach a piercing clip with a branch from a copper wire with a cross section of 10 mm2, which is inserted into the cabinet (or box) to the terminals of the input machine. We close the sections of the self-supporting insulated wire with sealed caps. Thus, we correctly "switched" from aluminum (self-supporting insulated wire) to copper. At the same time, we would not have any problems with connecting a copper wire (with a cross section of 10 mm2) to the terminals of the modular input machine. But representatives of gorseti will not accept such work.

Therefore, a self-supporting insulated wire wire with a cross section of 16 mm2 must be brought directly to the terminals of the input machine, which must be installed in a plastic box. It is very difficult to do this in practice, since it is necessary to maintain the degree of protection of the box (for outdoor installation, not lower than IP 54), while the self-supporting insulated wire must be fixed in relation to the plastic box, etc.

In practice, I just had to buy another steel cabinet, in which I installed the plastic boxes themselves, then the CIP wire was brought into the cabinet and fixed in it. The photo below shows the final work on the installation of the cabinet and its attachment to the facade of the house. The works were accepted without any comments or complaints.

Another important point that you need to pay attention to is related to the fact that the surge arrester, when operating during a thunderstorm, diverts current to the ground by connecting the surge arrester itself to the ground loop. In this case, currents can reach significant values: from 200 - 300 A and up to several thousand amperes. Therefore, it is important to provide the shortest path from the arrester themselves to the ground loop with a copper conductor with a cross section of at least 10 mm2. The photo below shows how I made this connection. For the reliability of the surge arrester, I made the connection of the devices to the ground loop with two copper wires with a cross section of 10 mm2 each. In the photo there is a wire in a yellow-green tube HERE (heat-shrinkable tube).

Installation of UZM-50M devices in a control cabinet

Performing electrical work does not cause problems, since the devices have a standard mounting on a DIN rail. A fragment of the work on the installation of the UZM-50M in the cabinet is shown in the photo below. The devices must also be installed in a plastic box with the possibility of sealing. The top cover of the box is not shown in the photo.

From the point of view of the electrical connection diagram (although the diagram is in the passport for the device and on the body of the device itself), an unprepared reader may have questions. To clarify the features of connecting the device, the figure below shows the connection diagram given in the passport for the UZM-50M, with some of my explanations.

Firstly, as can be seen from the diagram, the UZM-50M is a single-phase switching device and for its functioning requires the obligatory connection of the L and N conductors to the upper terminals. This is shown in the connection diagram in both cases (a and b). Further, a difference appears between scheme a and scheme b, about which the manufacturer does not give any explanation and the consumer has to figure out on his own how and in what cases which scheme to use.

The difference lies in the fact that according to the upper diagram (a), the load is connected to the device via two wires (L and N). That is, in the event of an emergency operation of the device, the circuit will be broken both along the phase conductor (L) and along the conductor (N).

In the lower diagram (b), the load is connected to the device only through one phase conductor (L), and the second wire (N) is connected to the load directly, bypassing the device. That is, in the event of an emergency operation of the device, it will only open the phase conductor, and the N conductor always remains connected. Based on the foregoing, and also knowing in which case it is allowed to break the conductor N, and in which it is not allowed, we can draw the following conclusion:

In the case of connecting a house (apartment) via a two-wire line (TN-C system), it is necessary to connect the UZM-50M apparatus according to the lower diagram (b), since in this case the N wire performs two functions (zero working conductor and zero protective conductor), and in no case should it be torn apart.

Surge arrester is an often overlooked but very important element. This element is recommended for installation by electrical equipment manufacturers, while opinions are divided among electricians themselves. Let's deal with this case. The most common questions about the arrester are as follows: What are the classes of arresters? What does it consist of and how does it work? How to connect a surge suppressor? Does it really protect electrical devices?

Arrester protection classes

In the voltage range below 1000 V, the arresters are divided into 4 classes, indicated by the letters of the alphabet: A, B, C and D.

1. Class A limiter not used in domestic installations, but used to protect power lines.
2. Class B protector Used to protect against high voltage surges such as those caused by lightning strikes to power lines.
3. Class C limiter designed for overvoltage protection with slightly lower mains voltages. Class B and C protection devices are usually installed in household switchgear.
4. Class D protector used for direct protection of selected electrical devices sensitive to impulse noise and surges in 220 V network. It is mounted in a switchboard, behind a socket in an electrical box, or directly in a protected device.

Each protection device limits the electrical potential to a certain level only. The closer the equipment is to the A class, the higher the power. For example:

• Class A will reduce the voltage level to 6 kV,
• Class B will reduce the voltage level to 2.5 kV,
• Class C will reduce the voltage level to 1.5 kV,
• Class D will reduce the voltage level to 0.8 kV.

Therefore, arresters of certain classes should be used in cascade, gradually reducing the level of the limiting voltage. That is, if there is one switchgear in the house, we use class B and C protective devices (there are 2 in 1 B + C protective devices at once).

If the building is multi-storey, class B protection devices must be used in the main distribution board, and class C arresters must be used in distribution boards in individual apartments.

If the device connected to the outlet is sensitive to voltage surges, we can also use class D arresters. We do not have access to class A arresters, this is the concern of the energy company.

Since we will consider home wiring, the article will be devoted to class B and class C (type I and II) protective devices.

Designation on schematic diagrams

The main symbols used in the designation of surge voltage arresters are as follows:

1. General designation of the arrester
2. Tubular arrester
3. Valve and solenoid arrester

Installing a surge arrester

A standard arrester B or C (possibly B + C) consists of two components:

1. Limiter base
2. Replaceable insert with protective element

The foundation

The base of the protective device is mounted on a TS35 DIN rail. It has two clamps. Connect phase (L) or neutral (N) wire on which too much electrical potential may appear. On the other side, connect the protective conductor PE, which is connected to the protective conductor of the switchgear.

The protective conductor must have a minimum cross-section of 4 mm2, but it will not hurt to take even more. Eventually there is a chance that a very high current will flow.

There are 3 pins under the PE terminal. As standard, the kit includes a plug that is inserted in the right place and allows you to connect the wires. Thanks to these clamps, there is the possibility of remote notification in case of damage to the insert or its burnout. This signal can be connected, for example, to the input of the alarm control unit (see diagram). In this case, the control panel will be informed about the damage to the insert by opening the electrical circuit between the red and green wires.

Insert

The insert contains all the most important elements due to which the defender functions correctly:

• Class B (Type I) - The basic element is simply a spark gap.
• Class C (type II) - here the varistor part is the main element.

How does a surge protector work

Protection is provided for devices powered from 220V mains cords connected to an arrester in a junction box. This applies to both phase and neutral conductors (depending on the selected type of protection).

The general rule is that on one side of the protective device we connect the phase conductors and possibly the neutral conductor, and on the other side the protective conductor.

When the voltage in the system is normal, the resistance between the wires is very high, on the order of several GigaOhms. As a result, no current flows through the arrester.

When a power surge occurs, current begins to flow through the arrester to ground.

In class B protective devices, the main element is the spark gap... During normal operation, its resistance is very high. In the case of a spark gap, this resistance is gigantic, since a spark gap is actually an open circuit. When lightning strikes an element of an electrical installation directly, the resistance of the spark gap drops to almost zero due to the electric arc. Due to the appearance of a very large electric potential in the spark gap between the previously separated elements, an electric arc is created.

Due to this, for example, a phase conductor with a large surge voltage and a protective conductor creates a short circuit and a large current flows directly to the ground, bypassing the internal electrical installation. After the discharge, the spark gap returns to its normal state - that is, it breaks the circuit.

The class C arrester has a varistor inside... A varistor is a specific resistor that has a very high resistance at a low electrical potential. If a voltage surge occurs in the system due to a discharge, its resistance decreases rapidly causing a current to flow to ground and a similar situation as in the case of a spark gap.

The difference between class B and class C is that the latter is capable of limiting surges with less potential than a direct lightning strike. The disadvantage of this solution is the rather rapid wear of the varistors.

The main thing in surge arresters, regardless of the class used, is the installation of grounding with very good parameters, that is, with a very low electrical resistance. If this resistance is too high, an overvoltage current (caused by a lightning strike) instead of a protector can flow through the electrical system and leave in the way burned-out equipment, which is currently connected to 220 volt outlets.

Connection diagram of the limiter to the network

How to connect the limiter to the home box? Let's start with the basics. We have a single-phase network and a single-module arrester. We want to protect the phase wire with it. Network type - TN-S.

We connect the phase supply conductor directly to the arrester and connect the arrester on the other side to the PE terminal block.

But this home switch is nothing more than a pulse limiter. Let's add the missing elements.

As you can see, the installation of a surge suppressor does not affect the further organization of the components in the home switchboard. The connection of the residual current device and the circuit breakers is carried out in the same way.

In general, in switchgears, class B, C or B + C surge voltage arresters are installed upstream of the circuit breaker (or circuit breakers) and overcurrent fuses. But the limiter is the first element underlying the protection of a house or apartment.

Three-phase installation

In a three-phase circuit, the width of the limiter and the number of protected connections are increased. However, the principle of operation of the limiter remains unchanged. The most commonly used three-layer system protective devices operating in a 4 + 0 system, which means connecting the following lines to the arrester:

• 3-phase wires
• 1 neutral wire

Each of the wires to be protected has equal rights, that is, possible overvoltages are eliminated by supplying current to the protective installation and, as a result, to the ground.

Of course, for TN-C installations (installation without a separate protective conductor) it is possible to purchase protective devices with only 3 protected connectors. Then, from the bottom, connect the limiter to the PEN (neutral protection) strip.

Safety and effectiveness of the limiter

In domestic installations, this is not often practiced, because the short-circuit protection exists in the form of a breaker or fuse, and its low rated current safely protects the network from failures.

Surge arrester parameters

Before you go to the store and buy this device, you need to know the following:

1. The number of modules (terminals) - depends on the type of your network. 1 module can be purchased when there is a single-phase TN-C system. 3 modules when the installation is in a three-phase TN-C network and 4 modules when the network is three-phase in TN-S or TT.
2. Class (type) - you can choose between classes B, C or B + C. If you are not sure that a type B limiter is used in front of your apartment, you should choose the B + C solution. Otherwise, a type C limiter will be enough.
3. The rated voltage at which the limiter operates.
4. Uc is the operating voltage of the protector, that is, the maximum voltage level that will lead to operation.
5. In is the rated current of the arrester, that is, what current can flow through the arrester in the event of a short circuit.
6. Imax is the current that the arrester is able to receive during an atmospheric discharge. Note that both values ​​(In = 30,000A and Imax = 60,000A) will be relatively large in relation to the current during normal use of appliances in the house.
7. Up - voltage to which it decreases in case of rupture. For example, if the potential reaches a voltage of 10,000 V in the event of a surge, the total value is reduced to 150.

Is it worth using the limiter on the network

Every electrician ponders whether it is worth buying an arrester at all. After all, this is not the cheapest element of electrical installation. Theoretically, during the repair or construction of wiring from scratch in an apartment or house, the cost of 3000 rubles (in the case of a 4-module protector) is a drop in the ocean of costs. In practice, the security block will not always have the opportunity to prove that it is needed. Even if it does, lowering the voltage may not always protect sensitive electronic devices (class D is better).

Any electrical equipment is created to work with a certain electrical energy, depending on the current and voltage in the network. When their value becomes more than the projected rate, then an emergency mode occurs.

Protection is designed to prevent the possibility of its formation or eliminate the destruction of electrical equipment. They are created for the specific conditions of the accident.

Features of protection of home wiring against overvoltage

The insulation of the household electrical network is calculated for the voltage limit value just above one to one and a half kilovolts. If it increases more, then a spark discharge begins to penetrate through the dielectric layer, which can develop into an arc that forms a fire.

To prevent its development, they create defenses that work according to one of two principles:

1. disconnecting the electrical circuit of a house or apartment from overvoltage;

2. removal of dangerous overvoltage potential from the protected area by quickly redirecting it to the ground contour.

With a slight increase in the voltage in the network, they are also called to correct the situation. But, for the most part, they are created to maintain the operating parameters of the power supply in a limited range of its regulation at the input, and not as a protective device. Their technical capabilities are limited.

In home wiring, voltage may rise:

1.for a relatively long period, when zero burns out in a three-phase circuit and the neutral potential shifts depending on the resistance of randomly connected consumers;

2. short-term impulse.

The first type of malfunction is successfully dealt with by the voltage monitoring relay. It constantly monitors the input parameters of the network and, when they reach the upper setting level, disconnects the circuit from the power supply until the failure is eliminated.

The reasons for the appearance of short-term overvoltage pulses can be two situations:

1. Simultaneous disconnection of several powerful consumers on the supply line, when the transformer substation does not have time to instantly stabilize the system;

2. strike of a lightning discharge of lightning in electrical equipment of power transmission lines, substations or houses.

The second scenario of the accident development represents the greatest danger than in all previous cases. The strength of the lightning current reaches enormous values. With averaged calculations, it is taken at 200 kA.

When it strikes the lightning rod and normal operation of the lightning protection of the building, it flows through the lightning rod on. At this moment, EMF is induced in all adjacent conductors according to the law of induction, the value of which is measured in kilovolts.

It can appear even in unplugged wiring and burn its equipment, including expensive TVs, refrigerators, computers.

Lightning can also strike an overhead power transmission line that feeds a building. In this situation, line arresters work normally, extinguishing its energy to the ground potential. But they are not capable of completely eliminating it.

Part of the high-voltage pulse through the wires of the connected circuit will spread in all possible directions and come to the input of a residential building, and from it - to all connected devices in order to burn their weakest points: electric motors and electronic components.

As a result, we got two options for damage to expensive household electrical equipment of a residential building during normal elimination of the consequences of a lightning strike into the lightning rod of our own building or power transmission line with standard protection. The conclusion suggests itself: it is necessary to install for them automatic protection against impulse discharges.

Types of surge suppressors for household wiring

The range of such protections is created for work in different conditions, differs in design, materials used, technology of work.

Principles of forming the element base of surge arresters

When creating overvoltage protection, the technical capabilities of various design solutions are taken into account. Gas-filled spark gaps are characterized by the fact that after the end of the passage of the discharge pulse, they support the flow of an additional current, which is close in magnitude to the short-circuit load. It is called the accompanying current.

Arresters providing a tracking current of the order of 100 ÷ 400 amperes can themselves become a source of fire and fail to provide protection. They cannot be installed to protect the insulation against breakdown between any phase, working and protective zero. Models of other types of arresters operate quite reliably within a 0.4 kV network.

In home wiring, overvoltage protection received priority varistor devices... Under normal operating conditions of an electrical installation, they create very small leakage currents of up to several milliamperes, and during the passage of a high-voltage pulse, the voltages are transferred as quickly as possible to tunnel mode, when they are capable of passing up to thousands of amperes.

Classes of insulation resistance of household electrical wiring to impulse overvoltages

The electrical equipment of residential buildings is created in four categories, which are denoted by Roman numerals IV ÷ I and are characterized by the maximum permissible overvoltage value of 6, 4, 2.5 and 1.5 kilovolts. Surge protection is designed for these zones.

In the technical literature, they are usually called "SPD", which stands for surge protection device... Manufacturers of electrical equipment for marketing purposes have introduced a more understandable definition for the common population - limiters. Other names can be found on the Internet.

Therefore, in order not to get confused in the terminology used, it is recommended to refer to the technical characteristics of the devices, and not just their name.

The following figure will help you understand the main parameters of the relationship between the categories of insulation resistance and the hazard zones of the building and the use of three classes of SPD for them.

It demonstrates that a 6 kilovolt impulse can arrive at the section from the transformer substation through the power line to the input board. Its value must be reduced by a class I surge arrester in zone 1 to four kV.

A class II arrester operates in the zone 2 switchboard, reducing the voltage to 2.5 kV. Inside a living room with zone 3, a class III SPD provides a total impulse reduction of up to 1.5 kilovolts.

As you can see, all three classes of arresters work in a complex, sequentially and alternately reduce the overvoltage pulse to the value admissible for the insulation of the electrical wiring.

If at least one of the constituent elements of this chain of protection turns out to be faulty, then the entire system will fail and an insulation breakdown will occur on the final device. It is necessary to use them in a complex manner, and during operation it is required to check the serviceability of the technical condition at least by external inspection.

Selection of varistors for different classes of surge arresters

Equipment manufacturers supply SPD devices with models of varistors, selected according to their current-voltage characteristics. Their type and operating limits are shown in the corresponding graph.

Each protection class has its own voltage and opening current. They can only be installed in their place.

Principles of forming circuits for switching overvoltage arresters

To protect the power supply line of an apartment, various principles for connecting an SPD can be used:

1.inphase;

2. antiphase;

3. combined.

In the first case, the longitudinal principle of protection of each wire against overvoltages relative to the ground contour is fulfilled, and in the second, the transverse principle between each pair of wires. Based on the collection of statistical data on fault handling and their analysis, it was revealed that the arising antiphase impulse overvoltages create more damage and are therefore considered the most dangerous.

The combined method allows you to combine both of the preceding methods.

Variants of connection diagrams of surge arresters for the TN-S earthing system

Scheme with electronic SPDs and arresters

In this scheme, SPDs of all three classes eliminate overvoltage pulses between the phases of the line and the working zero N along the "wire-wire" chains. The function of reducing common-mode overvoltages is assigned to arresters of a certain class by connecting them between the working and protective zero.

This method allows PE and N to be galvanically isolated from each other. The position of the neutral of a three-phase network depends on the symmetry of the applied loads in phases. It always has some kind of potential, which can be from fractions to several tens of volts.

If power supplies with a pulsed load operate in the system, then high-frequency interference from them can be transmitted through the potential equalization and grounding circuits through the PE conductor to sensitive electronic devices, interfering with their operation.

Turning on the arresters in this case reduces the effect of the listed factors due to better galvanic isolation than electronic arresters on varistors.

Circuits with electronic SPDs in protection classes I and II

In this scheme, protection against impulse voltages in the input and distribution boards is performed only by electronic arresters.

They remove all common-mode overvoltages (any wires to ground).

In Class III, the previous circuit with an electronic arrester and arrester works, providing wire-to-wire protection for the end user.

Features of the use of various models of surge arresters, taking into account the sequence of operation of the cascades

When operating the steps of protection against impulse overvoltage, their coordination and coordination are required. It is carried out by removing steps along a cable over a distance of more than 10 meters.

This requirement is explained by the fact that when a high-voltage pulse with a steep waveform enters the circuit, a voltage drop occurs due to the inductive resistance of the conductors. It is immediately applied to the first stage and triggers it. If this requirement is not met, then the steps are bypassed when the protection does not work correctly.

Subsequent protection cascades are connected according to the same principle.

When, according to the design features of the equipment, it is located close, then additional pulse-type dividing chokes are artificially included in the circuit, creating a delay chain. Their inductance is adjusted in the range of 6 ÷ 15 microhenry, depending on the type of power supply used in the building.

A variant of such a connection with a close location of the input and distribution boards and remote installation of end consumers is shown in the diagram.

When mounting chokes on such a system, one should take into account their ability to work reliably under the created loads, to withstand their limiting values.

For the convenience of maintenance, surge protection together with choke devices can be placed in a separate protective shield that serially connects the input device with the main switchboard of the house.

One of the variants of a similar design for a building made according to the TN-C-S grounding system is shown in the diagram below.

With this installation, all three classes of arresters can be placed in one place, which is convenient for maintenance. To do this, it is necessary to install isolation chokes in series between the protection stages.

Structurally, the input device, the main switchboard and the protective shield with this method of mounting the circuit should be located as close as possible.

The combined arrangement of the SPD and the chokes in one place - the protective shield - prevents overvoltage impulses from entering the main switchboard equipment, in which the PEN conductor is separated.

The connection of power cables to the main switchboard has features: they must be laid along the shortest paths, avoiding joint contact for sections of the protected circuit and without protection.

Modern manufacturers are constantly modifying their SPD designs using built-in impulse isolating reactors. They made it possible not only to locate the protection stages at a short distance along the cable, but also to combine them in a separate block.

Now on the market, taking into account the implementation of this method, there are SPD designs of combined classes I + II + III or I + II. A different range of models of such arresters is produced by the Russian company Hakel.

They are created for different building grounding systems, they work without installing additional stages of protection, but they require certain technical installation conditions to be met along the length of the cable to be connected. In most cases, it should be less than 5 meters.

For the normal operation of electronic equipment and its protection against high frequency interference, various filters are available, which include class III SPDs. They need to be connected to the ground loop through a PE conductor.

Features of protection of complex household appliances from overvoltage impulses

The life of a modern person dictates the need to use various electronic devices that process and transmit information. They are quite sensitive to high-frequency interference and impulses, they do not work well or even fail when they appear. To eliminate such failures, an individual grounding of the device case, called functional grounding, is used.

It is electrically separated from the PE protective conductor. However, when lightning strikes the lightning protection between the building or line earthing and the functional electronic device, a discharge current will flow along the earth contour, caused by the applied high-voltage overvoltage pulse.

It can be eliminated by equalizing the potentials of these circuits by installing a special arrester between them, which will equalize the potentials of the circuits in case of accidents and provide galvanic isolation in everyday operating conditions.

Hakel also specializes in the production of such arresters.

Additional requirement for protection of arresters against short circuits

All SPDs are included in the circuit to equalize the potentials between its various parts in critical situations. It should be borne in mind that they themselves, despite the presence of built-in thermal protection of the varistors, can be damaged and, because of this, become a source of a short circuit, which develops into a fire.

Protection on varistors can fail in case of prolonged excess of the rated voltage, associated, for example, with zero burn-off in a three-phase supply network. Dischargers, unlike electronics, are not equipped with thermal protection at all.

For these reasons, all SPD structures are additionally protected by overload and short circuit fuses. They have a special complex design and are very different from models with a simple fuse-link.

The use of circuit breakers for such situations is not always justified: they are damaged by lightning impulses when the power contacts are welded.

Using the SPD protection circuit with fuses, it is necessary to observe the principle of creating its hierarchy using selectivity methods.

As you can see, in order to ensure reliable protection of home electrical wiring from surges, it is necessary to carefully approach this issue, analyze the probability of accidents in the design scheme, taking into account the working grounding system, and select the most suitable surge arresters for it.

If your house has a lot of expensive household appliances, it is better to take care of the organization of comprehensive power grid protection. In this article we will tell you about surge protection devices, why they are needed, what are they and how they are installed.

The nature of surge voltages and their effect on technology

Since childhood, many are familiar with the bustle of disconnecting household electrical appliances from the network at the first sign of an impending thunderstorm. Today, the electrical equipment of urban networks has become more advanced, which is why many neglect basic protection devices. At the same time, the problem has not completely disappeared, household appliances, especially in private houses, are still at risk.

The nature of the occurrence of impulse overvoltages (IP) can be natural and man-made. In the first case, IPs arise due to lightning striking overhead power lines, and the distance between the point of impact and consumers at risk can be up to several kilometers. A strike is also possible on the radio masts and lightning rods connected to the main grounding circuit, in which case an induced overvoltage appears in the household network.

1 - remote lightning strike in power lines; 2 - consumers; 3 - ground loop; 4 - close lightning strike in power lines; 5 - direct lightning strike to a lightning rod

Man-made IP are unpredictable, they arise as a result of switching overloads at transformer and distribution substations. With an asymmetric increase in power (only on one phase), a sharp voltage surge is possible, it is almost impossible to foresee this.

Impulse voltages are very short in time (less than 0.006 s), they appear in the network systematically and most often pass unnoticed by the observer. Household appliances are designed to withstand overvoltages up to 1000 V, which appear most often. At a higher voltage, failure of the power supplies is guaranteed, insulation breakdown in the house wiring is also possible, which leads to multiple short circuits and fire.

How does an SPD work and how does it work?

SPD, depending on the protection class, can have a semiconductor device on varistors, or have a contact arrester. In normal mode, the SPD operates in bypass mode, the current inside it flows through the conductive shunt. The shunt is connected to the protective ground through a varistor or two electrodes with a strictly regulated gap.

With a voltage jump, even a very short one, the current passes through these elements and spreads along the ground or is compensated by a sharp drop in resistance in the phase-zero loop (short circuit). After the voltage stabilizes, the arrester loses its capacity and the device works in normal mode again.

Thus, the SPD closes the circuit for a while so that the excess voltage can be converted into heat energy. At the same time, significant currents pass through the device - from tens to hundreds of kiloamperes.

What is the difference between protection classes

Depending on the reasons for the occurrence of IP, two characteristics of the overvoltage wave are distinguished: 8/20 and 10/350 microseconds. The first digit is the time it takes for the MT to reach its maximum value, the second is the time it takes to fall to nominal values. As you can see, the second type of overvoltage is more dangerous.

Class I devices are designed for protection against power supply with a characteristic of 10/350 μs, which most often occur during a lightning discharge in a power transmission line closer than 1500 m to the consumer. The devices are capable of passing a current of 25 to 100 kA through themselves for a short time; practically all class I devices are based on arresters.

Class II SPDs are designed to compensate for power supplies with a characteristic of 8/20 μs, the peak current values ​​in them vary from 10 to 40 kA.

Protection class III is designed to compensate for overvoltages with currents less than 10 kA with a power supply characteristic of 8/20 μs. Devices of protection class II and III are based on semiconductor elements.

It may seem that it is enough to install only Class I devices, as the most powerful, but this is not so. The problem is that the higher the lower threshold of the throughput current, the less sensitive the SPD is. In other words: with short and relatively low values ​​of the power supply, a powerful SPD may not work, and a more sensitive one will not cope with currents of this magnitude.

Devices with protection class III are designed to eliminate the lowest power supplies - only a few thousand volts. They are completely similar in characteristics to protection devices installed by manufacturers in power supplies for household appliances. With a redundant installation, they are the first to take on the load and prevent the operation of an SPD in devices whose resource is limited to 20-30 cycles.

Is there a need for an SPD, risk assessment

A complete list of requirements for the organization of protection against power supply is set out in IEC 61643-21, it is possible to determine the mandatory installation according to the IEC 62305-2 standard, according to which a specific assessment of the degree of risk of lightning strike and the consequences caused by it is established.

In general, when supplying power from overhead transmission lines, the installation of class I SPDs is almost always preferable, unless a set of measures has been taken to reduce the effect of thunderstorms on the power supply mode: re-grounding of supports, PEN-conductor and metal bearing elements, a lightning rod with a separate ground loop, installation potential equalization systems.

An easier way to assess risk is to compare the cost of unprotected appliances and security devices. Even in multi-storey buildings, where overvoltages are very low with the 8/20 characteristic, the risk of insulation breakdown or failure of devices is quite high.

Installation of devices in the main switchboard

Most SPDs are modular and can be installed on a 35 mm DIN rail. The only requirement is that the shield for installing the SPD must have a metal case with a mandatory connection to the protective conductor.

When choosing an SPD, in addition to the basic performance characteristics, you should also take into account the rated operating current in bypass mode, it must correspond to the load in your mains. Another parameter is the maximum limiting voltage, it should not be lower than the highest value within the daily fluctuations.

SPDs are connected in series to a single-phase or three-phase supply network, respectively, through a two-pole and four-pole circuit breaker. Its installation is necessary in case of soldering the spark gap electrodes or breakdown of the varistor, which causes a permanent short circuit. Phases and a protective conductor are connected to the upper terminals of the SPD, and zero to the lower terminals.

Example of SPD connection: 1 - input; 2 - automatic switch; 3 - SPD; 4 - grounding bus; 5 - ground loop; 6 - electricity meter; 7 - differential machine; 8 - to consumers' machines

When installing several protective devices with different protection classes, they must be coordinated using special chokes connected in series with the SPD. Protective devices are built into the circuit in ascending order of class. Without coordination, more sensitive SPDs will take on the main load and fail earlier.

The installation of chokes can be avoided if the length of the cable line between the devices is more than 10 meters. For this reason, class I SPDs are mounted on the facade even before the meter, protecting the metering unit from overvoltage, and the second and third class are installed, respectively, on the ASU and floor / group shields.

The surge arrester is one of the most widely known high voltage devices used for network protection.

Description of the fixture

To begin with, it is worth explaining why, in principle, impulse overvoltages arise and how they are dangerous. The reason for the appearance of this process is a violation in the atmospheric or commutation process. Such defects are quite capable of causing tremendous damage to electrical equipment that is exposed to such effects.

Here it is worth giving an example on a lightning rod. This device does an excellent job of discharging a strong discharge that hits an object, but it will not be able to help in any way if the discharge enters the network through overhead lines. If this happens, then the very first conductor that gets in the way of such a discharge will fail, and it can also cause damage to other electrical equipment that is connected to the same electrical network. Elementary protection - turning off all devices during a thunderstorm, but in some cases this is not possible, and therefore devices such as surge arresters were invented.

What will the use of the device give

If we talk about conventional protective equipment, then their design is slightly worse than that of an arrester. In the usual version, carborundum resistors are installed. An additional design is spark gaps, which are interconnected in a sequential manner.

In surge arresters, there are elements such as non-linear transistors. Zinc oxide became the basis for these elements. There are several such parts, and they are all combined into one column, which is placed in a special case made of a material such as porcelain or polymer. This ensures a completely safe use of such devices, and also reliably protects them from any external influences.

It is important to note here that the main feature of the surge arrester is the design of zinc oxide resistors. This design allows you to greatly expand the functions that the device can perform.

Technical specifications

Like any other device, a surge arrester has a basic characteristic that determines its performance and quality. In this case, such an indicator was the value of the operating voltage, which can be supplied to the terminals of the device without any time limit.

There is one more characteristic - conduction current. This is the value of the current that passes through the device under the influence of voltage. This indicator can be measured only in the conditions of real use of the device. The main numerical indicators of this parameter are capacity and activity. The overall indicator of this characteristic can reach several hundred microamperes. The obtained value of this characteristic is used to evaluate the performance of the surge arrester.

Arrester device description

In order to manufacture this device, manufacturers use the same electrical and design methods that are used in the manufacture of other products. This is most noticeable when examining the dimensions and materials used to make the case. The appearance also has some similarities with other devices. However, it is worth noting that special attention is paid to such things as the installation of a surge suppressor, as well as its further connection to general consumer-type electrical installations.

There are several requirements that apply to this particular class of devices. The arrester housing must be completely protected from direct human contact. The risk that the device will catch fire due to possible overloads must be completely excluded. If the element fails, then this should not entail a short circuit in the line.

Purpose and application of surge arresters

The main purpose of nonlinear surge arresters is to isolate electrical equipment from atmospheric or switching overvoltages. This device belongs to the group of high-voltage devices.

In these devices, there is no such section as the spark gap. If we compare the operating range of an arrester and a conventional one, then the arrester is able to withstand deeper voltage drops. The main task of this device is to withstand these loads without a time limit. Another significant difference between a surge arrester and a conventional valve is that the dimensions, as well as the physical weight of the structure, in this case are much lower. The presence of such an element as a lid made of porcelain or polymers has led to the fact that the inside of the device is reliably protected from external environmental influences.

OPN-10

The device of this device is somewhat different from a conventional surge arrester. In this embodiment, a column of varistors is used, which are enclosed in a tire. To create a tire, in this case, not porcelain or polymers are used, but a fiberglass pipe, onto which a track-resistant silicone rubber shell is pressed. In addition, the column of varistors has aluminum leads, which are pressed on both sides, and also screwed into the pipe.