A circuit breaker release (automatic) is an electrical device that turns off the network if a large electric current occurs in it. This device is used to prevent a fire in the house from overheating, and expensive household appliances did not fail.
Types of switches
All machines are divided according to the type of release. They are divided into 6 types:
- thermal;
- electronic;
- electromagnetic;
- independent;
- combined;
- semiconductor.
They recognize very quickly emergency situations, such as:
- the occurrence of overcurrents - an increase in the current strength in the electrical network that exceeds the rated current of the circuit breaker;
- voltage overload – short circuit in the circuit;
- voltage fluctuations.
At these moments, the contacts in the automatic releases open, which prevents serious consequences in the form of damage to wiring and electrical equipment, which very often leads to fires.
Thermal switch
It consists of a bimetallic plate, one of the ends of which is located next to the release device of the automatic release. The plate is heated by the current passing through it, hence the name. When the current begins to increase, it bends and touches the trigger bar, which opens the contacts in the “machine”.
The mechanism operates even with slight excesses of the rated current and an increased response time. If the load increase is short-term, the switch does not trip, so it is convenient to install it in networks with frequent but short-term overloads.
Advantages of a thermal release:
- absence of contacting and rubbing surfaces;
- vibration stability;
- budget price;
- simple design.
The disadvantages include the fact that its operation largely depends on the temperature regime. It is better to place such machines away from heat sources, otherwise there is a risk of numerous false alarms.
Electronic switch
Its components include:
- measuring devices (current sensors);
- control unit;
- electromagnetic coil (transformer).
At each pole of the electronic circuit breaker there is a transformer that measures the current passing through it. The electronic module that controls the trip processes this information, comparing the obtained result with the specified one. In the event that the resulting indicator is greater than the programmed one, the “machine” will open.
There are three trigger zones:
- Long delay. Here, the electronic release serves as a thermal release, protecting the circuits from overloads.
- Short delay. Provides protection against minor short circuits that usually occur at the end of the protected circuit.
- The working area “instantly” provides protection against high-intensity short circuits.
Pros – large selection settings, maximum accuracy of the device to a given plan, the presence of indicators. Cons: sensitivity to electromagnetic fields, high price.
Electromagnetic
This is a solenoid (a coil of wound wire), inside of which there is a core with a spring that acts on the release mechanism. This is an instant action device. As the supercurrent flows through the winding, a magnetic field is generated. It moves the core and, exceeding the force of the spring, acts on the mechanism, turning off the “automatic machine”.
Pros: resistance to vibration and shock, simple design. Cons – forms a magnetic field, triggers instantly.
This is an additional device to automatic releases. With its help, you can turn off both single-phase and three-phase circuit breakers located at a certain distance. To activate the independent release, voltage must be applied to the coil. To return the machine to its original position, you must manually press the “return” button.
Important! The phase conductor must be connected from one phase from under the lower terminals of the switch. If it is connected incorrectly, the independent switch will fail.
Basically, independent automatic machines are used in automation panels in highly ramified power supply devices of many large facilities, where control is transferred to the operator’s console.
Combination switch
It has both thermal and electromagnetic elements and protects the generator from overloads and short circuits. To operate the combined automatic release, the current of the thermal circuit breaker is indicated and selected: the electromagnet is designed for 7–10 times the current, which corresponds to the operation of heating networks.
The electromagnetic elements in the combination switch provide instantaneous protection against short circuits, and the thermal elements protect against overloads with a time delay. The combined machine is switched off when any of the elements is triggered. During short-term overcurrents, none of the types of protection are triggered.
Semiconductor switch
It consists of alternating current transformers, magnetic amplifiers for direct current, a control unit and an electromagnet that functions as an independent automatic release. The control unit helps set the selected contact release program.
Its settings include:
- regulation of the rated current in the device;
- setting the time;
- triggered when a short circuit occurs;
- protective switches against overcurrent and single-phase short circuit.
Pros - a large selection of regulation for different power supply schemes, ensuring selectivity to series-connected circuit breakers with fewer amperes.
Cons: high cost, fragile control components.
Installation
Many home-grown electricians believe that installing a machine is not difficult. This is fair, but it must be done certain rules. Releases circuit breaker, just like plug fuses, must be connected to the network so that when the plug of the machine is turned out, its screw sleeve is without voltage. The connection of the supply conductor for one-way power supply to the machine must be made to the fixed contacts.
Installation of an electric single-phase two-pole circuit breaker in an apartment consists of several stages:
- securing the switched-off device to the electrical panel;
- connecting wires without voltage to the meter;
- connecting voltage wires to the machine from above;
- turning on the machine.
Fastening
We install a DIN rail in the electrical panel. Cutting off right size and fasten it with self-tapping screws to the electrical panel. We snap the automatic circuit breaker onto the DIN rail using a special lock, which is located on the back of the machine. Make sure that the device is in shutdown mode.
Connection to the electricity meter
We take a piece of wire, the length of which corresponds to the distance from the meter to the machine. We connect one end to the electric meter, the other to the terminals of the release, observing the polarity. We connect the supply phase to the first contact, and the neutral supply wire to the third. Wire cross-section – 2.5 mm.
Connecting voltage wires
From the central electrical distribution panel, the supply wires are connected to the apartment panel. We connect them to the terminals of the machine, which must be in the “off” position, observing the polarity. The wire cross-section is calculated depending on the energy consumed.
Turning on the machine
Only after all the wires have been installed correctly can the automatic current release be put into operation.
It happens that the constant shutdown of the machine becomes a big problem. Do not try to solve this by installing a trip unit with a higher current rating. Such devices are installed taking into account the cross-section of the wires in the house, and, perhaps, a large current in the network is unacceptable. The problem can only be solved by inspecting the electrical supply system of the apartment by professional electricians.
Hello friends. The topic of the post is the types and types of circuit breakers (automatic circuit breakers, AB). I also want the results of the crossword puzzle tournament.
Types of machines:
Can be divided into AC, DC and universal switches operating at any current.
Design - there are air, modular, in a molded case.
Rated current indicator. The minimum operating current of a modular machine is 0.5 Ampere, for example. Soon I will write about how to choose the right rated current for a circuit breaker, subscribe to the blog news so as not to miss it.
Voltage rating is another difference. In most cases, AVs operate in networks with a voltage of 220 or 380 Volts.
There are current-limiting and non-current-limiting.
All switch models are classified by the number of poles. They are divided into single-pole, double-pole, three-pole and four-pole circuit breakers.
Types of releases - maximum current release, independent release, minimum or zero voltage release.
Speed of operation of circuit breakers. There are high-speed, normal and selective automatic machines. They are available with or without a time delay, independent or inversely dependent on the current response time delay. Characteristics can be combined.
They differ in the degree of protection against environment— IP, mechanical influences, conductivity of the material. By type of drive - manual, motor, spring.
By the presence of free contacts and the method of connecting conductors.
Types of machines:
What does type AB mean?
Automatic circuit breakers contain two types of circuit breakers - thermal and magnetic.
Magnetic quick-release switch is designed for short-circuit protection. The tripping of the circuit breaker can occur in a time from 0.005 to several seconds.
The thermal breaker is much slower, designed to protect against overload. It works using a bimetallic plate that heats up when the circuit is overloaded. Response time ranges from a few seconds to minutes.
The combined response characteristic depends on the type of connected load.
There are several types of AV shutdown. They are also called types of time-current shutdown characteristics.
A, B, C, D, K, Z.
A– used for breaking circuits with long electrical wiring, serves as good protection for semiconductor devices. They operate at 2-3 rated currents.
B– for a general purpose lighting network. They operate at 3-5 rated currents.
C– lighting circuits, electrical installations with moderate starting currents. These can be motors, transformers. The overload capacity of the magnetic circuit breaker is higher than that of type B switches. They operate at 5-10 rated currents.
D– used in circuits with active-inductive loads. For electric motors with high starting currents, for example. At 10-20 rated currents.
K– inductive loads.
Z– for electronic devices.
It is better to look at the data on the operation of switches of types K, Z in the tables specifically for each manufacturer.
That seems to be all, if there is anything to add, leave a comment.
Overloads in electrical circuits are common. To protect electrically powered devices from such voltage surges, circuit breakers were invented. Their task is simple - to break the electrical circuit if the voltage exceeds the nominal limits.
The first such devices were the familiar traffic jams, which are still installed in some apartments. As soon as the voltage jumps above 220 V, they are knocked out. Modern types of circuit breakers are not only plugs, but also many other varieties. Their great feature is their reusability.
Classification
Modern GOST 9098-78 distinguishes 12 classes of circuit breakers:
This classification of circuit breakers is very convenient. If you wish, you can figure out which device to install in your apartment and which for production.
Types (species)
GOST R 50345-2010 divides circuit breakers into the following types (the division is based on sensitivity to overloads), marked with letters of the Latin alphabet:
These are the main circuit breakers used in residential buildings and apartments. In Europe, the marking begins with the letter A - the most overload-sensitive circuit breakers. They are not used for domestic needs, but are actively used to protect power circuits of precision instruments.
There are also three more markings - L, Z, K.
Distinctive design features
Automatic devices consist of the following components:
- main contact system;
- arc chute;
- main drive of the tripping device;
- various types of release;
- other auxiliary contacts.
The contact system can be multi-stage (one-, two- and three-stage). It consists of arc extinguishing, main and intermediate contacts. Single-stage contact systems are mainly made from cermets.
To somehow protect parts and contacts from destructive forces electric arc reaching 3,000° C, an arc-extinguishing chamber is provided. It consists of several arc extinguishing grids. There are also combined devices, capable of extinguishing a high current electric arc. They contain slot chambers along with a grille.
For any circuit breaker there is a current limit. Thanks to the protection of the machine, it cannot cause damage. With huge overloads of such current, the contacts can either burn out or even weld to each other. For example, for the most common household appliances with an operating current of 6 A to 50 A, the maximum current can range from 1000 A to 10,000 A.
Modular designs
Designed for low currents. Modular circuit breakers consist of separate sections (modules). The entire structure is mounted on a DIN rail. Let's take a closer look at the design of a modular switch:
- On/off is done using a lever.
- The terminals to which the wires are connected are screw terminals.
- The device is fixed to the DIN rail with a special latch. This is very convenient because such a switch can be easily removed at any time.
- The entire electrical circuit is connected through movable and fixed contacts.
- Disengagement occurs using some kind of release (thermal or electromagnetic).
- The contacts are specially placed next to the arc chute. This is due to the occurrence of a powerful electric arc during disconnection of the connection.
BA series – industrial switches
Representatives of these machines are primarily intended for use in AC electrical circuits at 50-60 Hz, with an operating voltage of up to 690 V. They are also used with a direct current of 450 V and a current of up to 630 A. Such switches are designed for very rare operational use ( no more than 3 times per hour) and protection of lines from short circuits and electrical overloads.
Among the important characteristics of this series are:
- high breaking capacity;
- wide range of electromagnetic releases;
- button for testing the device with free release;
- load switches with special protection;
- remote control through a closed door.
AP series
The automatic circuit breaker is capable of protecting electrical installations and motors from sudden voltage surges and short circuits within the network. The launches of such mechanisms are not intended to be very frequent (5-6 times per hour). The automatic circuit breaker can be two-pole or three-pole.
All structural elements are located on a plastic base, which is closed with a lid on top. At large overloads, the free release mechanism is activated, and the contacts automatically open. In this case, the thermal release maintains the response time, and the electromagnetic release provides instantaneous disconnection in the event of a short circuit.
When operating the machine, it is advisable to adhere to the following conditions:
- When air humidity is 90%, the temperature should not exceed 20 degrees.
- The operating temperature ranges from -40 to +40 degrees.
- Vibration at the mounting location should not exceed 25 Hz.
It is strictly prohibited to work in an explosive environment containing gases that destroy metal and windings, near clean energy heating devices, water flows and splashes, in places with conductive dust.
The variety of automatic switches allows you to easily select a device for an apartment or house. It is best to invite a specialist to install it.
At practical application It is important not only to know the characteristics of circuit breakers, but also to understand what they mean. Thanks to this approach, most technical issues can be resolved. Let's look at what is meant by certain parameters indicated on the label.
Abbreviation used.
Device markings contain all necessary information, describing the main characteristics of circuit breakers (hereinafter referred to as AB). What they mean will be discussed below.
Time-current characteristic (VTC)
Using this graphical display, you can get a visual representation of the conditions under which the circuit power-off mechanism will be activated (see Fig. 2). On the graph, the time required to activate the AB is displayed as a vertical scale. The horizontal scale shows the I/In ratio.
Rice. 2. Graphic display of time and current characteristics of the most common types of machinesThe permissible excess of the standard current determines the type of time-current characteristics for releases in devices that perform automatic shutdown. In accordance with current regulations (GOST P 50345-99), each type is assigned a specific designation (from Latin letters). The permissible excess is determined by the coefficient k=I/In; for each type, the values established by the standard are provided (see Fig. 3):
- “A” – maximum – three times excess;
- “B” - from 3 to 5;
- “C” - 5-10 times more than standard;
- “D” - 10-20 times excess;
- "K" - from 8 to 14;
- "Z" - 2-4 more than standard.
Figure 3. Basic activation parameters for various types
Note that this graph fully describes the activation conditions of the solenoid and thermoelement (see Fig. 4).
Taking into account all of the above, we can summarize that the main protective characteristic of an AV is due to the time-current dependence.
List of typical time-current characteristics.
Having decided on the labeling, let’s move on to considering the various types of devices that meet a certain class depending on the characteristics.
Characteristic type "A"
AB thermal protection of this category is activated when the ratio of the circuit current to the rated current (I/I n) exceeds 1.3. Under these conditions, shutdown will occur after 60 minutes. As the rated current is further exceeded, the tripping time becomes shorter. Activation of electromagnetic protection occurs when the nominal value is doubled, the response speed is 0.05 seconds.
This type is installed in circuits not subject to short-term overloads. As an example, we can cite circuits based on semiconductor elements, when they fail, the excess current is insignificant. This type is not used in everyday life.
Characteristic "B"
The difference between this type and the previous one is the operating current; it can exceed the standard one from three to five times. In this case, the solenoid mechanism is guaranteed to be activated at a five-fold load (de-energization time - 0.015 seconds), the thermoelement - three times (it will take no more than 4-5 seconds to turn off).
These types of devices have found application in networks that are not characterized by high inrush currents, for example, lighting circuits.
Characteristic "C"
This is the most common type, its permissible overload is higher than that of the two previous types. When the normal operating mode is exceeded five times, the thermocouple is triggered; this is a circuit that turns off the power supply within one and a half seconds. The solenoid mechanism is activated when the overload exceeds the norm by ten times.
These AVs are designed to protect an electrical circuit in which a moderate inrush current may occur, which is typical for a household network, which is characterized by a mixed load. When buying a device for your home, it is recommended to choose this type.
Legrand three-pole circuit breaker Characteristic "D"
ABs of this type are characterized by high overload characteristics. Namely, ten times the norm for the thermoelement and twenty times for the solenoid.
Such devices are used in circuits with high inrush currents. For example, to protect starting devices of asynchronous electric motors. Figure 9 shows two devices in this group (a and b).
Figure 9. a) VA51-35; b) BA57-35; c) BA88-35 Characteristic "K"
For such AVs, activation of the solenoid mechanism is possible when the current load exceeds 8 times, and is guaranteed to occur when there is a twelve-fold overload of the normal mode (eighteen-fold for DC voltage). Load disconnection time is no more than 0.02 seconds. As for the thermoelement, its activation is possible when it exceeds 1.05 from the standard mode.
Scope of application: circuits with inductive loads.
Characteristic "Z"
This type is distinguished by a small permissible excess of the standard current, the minimum limit is two times the standard current, the maximum is four times. The thermoelement response parameters are the same as those of AB with characteristic K.
This subtype is used for connecting electronic devices.
Characteristics "MA"
A distinctive feature of this group is that a thermoelement is not used to disconnect the load. That is, the device only protects against short circuits, which is quite enough to connect an electric motor. Figure 9 shows such a device (c).
Normal operation current
This parameter describes as much as possible valid value for normal operation, if it is exceeded, the load shedding system will be activated. Figure 1 shows where this value is displayed (using IEK products as an example).
Thermal parameters
This term refers to the operating conditions of the thermoelement. This data can be obtained from the corresponding time-current graph.
Ultimate breaking capacity (UCC).
This term refers to the maximum permissible load value at which the device can open the circuit without loss of functionality. In Figure 5, this marking is indicated by a red oval.
Rice. 5. Device from Schneider Electric Current limiting categories
This term is used to describe the ability of an AV to trip a circuit before the short-circuit current in it reaches its maximum. The devices are produced with current limiting of three categories, depending on the load disconnection time:
- 10 ms. and more;
- from 6 to 10 ms;
- 2.5-6 ms.
Note that ABs belonging to the first category may not have appropriate markings.
A small life hack on how to choose the right switch for your home
A circuit breaker is an electrical device, the main purpose of which is to switch its operating state when a certain situation occurs. Electrical circuit breakers combine two devices: a regular switch and a magnetic (or thermal) release, the task of which is to timely break the electrical circuit if the threshold current value is exceeded. Circuit breakers, like all electrical devices, also have different varieties, which divides them into certain types. Let's take a look at the main classifications of circuit breakers.
1" Classification of machines by number of poles:
A) single-pole circuit breakers
b) single-pole circuit breakers with neutral
c) two-pole circuit breakers
d) three-pole machines
e) three-pole circuit breakers with neutral
e) four-pole machines
2" Classification of automatic machines according to the type of releases.
The design of various types of circuit breakers usually includes 2 main types of releases (breakers) - electromagnetic and thermal. Magnetic circuit breakers are used for electrical protection against short circuits, while thermal circuit breakers are intended mainly to protect electrical circuits against a certain overload current.
3" Classification of automatic machines according to tripping current: B, C, D, (A, K, Z)
GOST R 50345-99, based on instantaneous tripping current, automatic machines are divided into the following types:
A) type “B” - over 3 In to 5 In inclusive (In is the rated current)
b) type “C” - over 5 In up to 10 In inclusive
B) type “D” - over 10 In to 20 In inclusive
Machine manufacturers in Europe have a slightly different classification. For example, they have an additional type “A” (over 2 In to 3 In). Some manufacturers of circuit breakers also have additional switching curves (ABB has circuit breakers with K and Z curves).
4" Classification of machines according to the type of current in the circuit: constant, variable, both.
Rated electric currents for the main circuits of the release are selected from: 6.3; 10; 16; 20; 25; 32; 40; 63; 100; 160; 250; 400; 630; 1000; 1600; 2500; 4000; 6300 A. Automatic machines are also additionally produced with rated currents of the main electrical circuits of the automatic machines: 1500; 3000; 3200 A.
5" Classification according to the presence of current limitation:
a) current-limiting
b) non-current limiting
6" Classification of automatic machines by types of releases:
A) with overcurrent release
b) with independent release
c) with minimum or zero voltage release
7" Classification of machines according to time delay characteristics:
A) without time delay
b) with a time delay independent of current
c) with a time delay inversely dependent on the current
d) with a combination of the specified characteristics
8" Classification according to the presence of free contacts: with and without contacts.
9" Classification of machines according to the method of connecting external wires:
A) with rear connection
b) with front connection
c) with combined connection
d) with universal connection (both front and rear).
10" Classification by type of drive: with manual, motor and spring.
P.S. Everything has its own varieties. After all, if there was only one thing in its only copy, it would be, at a minimum, simply boring and too limited! The good thing about the variety is that you can choose exactly what best suits your needs.
Any circuit breaker has an important component of the device: a release, which serves to open or close the switching device. Essentially, the release opens the contacts of the circuit breaker when overcurrents occur and the voltage decreases. GOST R 50030.1 (5) defines the concept of a release as “A device mechanically connected to a contact switching device, which releases the holding devices and thereby allows the opening or closing of the switching device.” Standard IEC 61992‑1 (6) complements this definition of a circuit breaker release - the release may consist of mechanical, electronic or electromagnetic components; refers to any device with a mechanical action that is used for tripping operation when certain conditions are encountered in the input circuit; a machine may have several releases.
Types of releases
The following types of releases are most often found in household circuit breakers: thermal, electronic and electromagnetic. They quickly recognize a critical situation (the appearance of overcurrents, overloads and voltage surges) and open the circuit breaker contacts, preventing damage to electrical equipment and protecting the wiring. In addition to these types, there are also zero-voltage, minimum-voltage, independent, semiconductor, and mechanical releases.
Overcurrents - an increase in current in the electrical network exceeding the rated current of the machine. These are overload and short circuit currents.
Overload current - overcurrent in a functional network.
Short circuit current is an overcurrent resulting from the short circuit of two network components with extremely low resistance between these elements.
Thermal release
The thermal release opens the contacts of the circuit breaker when the rated current is slightly exceeded and is characterized by an increased response time. In case of short-term excesses of the current load, it does not operate; this is convenient in networks where short-term excesses of the rated current of the machine are frequent.
The thermal release is a bimetallic strip, one end of which is located next to the release trigger. If the current increases, the plate begins to bend and approach the trigger mechanism, touches the bar, and it, in turn, opens the contacts of the circuit breaker. The operating principle is based on the physical properties of metal, which expands when heated, which is why such a release is called thermal.
The advantages of a thermal release include the absence of surfaces rubbing against each other, resistance to vibration, and low cost due to its simple design. But you also need to pay attention to the disadvantages - the operation of a thermal release is highly dependent on the ambient temperature, they should be placed in places with a stable temperature, away from heat sources, otherwise numerous false alarms are possible.
Electronic release
The electronic release includes measuring devices (current sensors), a control unit and an actuating electromagnet. Electronic releases are designed to issue a command to automatically turn off the machine with a given program when an overcurrent or short circuit occurs in the electrical circuit. When the current through the circuit breaker is exceeded, the electronic release unit begins counting the response time in accordance with the time-current characteristic. If during the actuation time the current decreases to a value below the threshold, then automatic operation will not occur.
The advantages of electronic releases include: a wide range of settings, strict adherence of the device to a given program, and the presence of indicators. The main disadvantage is the rather high cost, as well as the sensitivity of the release to the effects of electromagnetic radiation.
Electromagnetic release
The electromagnetic release (cut-off) operates instantly, preventing the slightest possibility of damage to the components of the electrical circuit. This is a solenoid with a movable core that acts on the tripping mechanism. As current flows through the solenoid winding, if the current load is exceeded, the core is retracted under the influence of the electromagnetic field.
The electromagnetic release is triggered when the short circuit current is exceeded. It has sufficient strength, is resistant to vibration, but creates a magnetic field.
Circuit breaker release current
The current of the circuit breaker release has a specific value (nominal), meaning the amount of current at which the circuit breaker will open the circuit. The current in the thermal release is always equal to or less than the rated current of the circuit breaker. If the current load on the release is exceeded in any way, the machine will shut down. In this case, the time after which the contacts open depends on the time of flow of the current of the excess load. The tripping time of the thermal release can be calculated using the time-current characteristics.
The current of the electromagnetic release switches off the circuit breaker instantly when the rated current of the circuit breaker is exceeded, most often this happens during a short circuit. Before a short circuit, the current in the network increases very quickly, which is taken into account by the electromagnetic release device, resulting in a very rapid impact on the release mechanism. The response speed in this case is a fraction of a second.
They can be equipped with the following releases built into them:
Electromagnetic or electronic overcurrent release of instantaneous or delayed action with a time delay practically independent of the current;
Electrothermal or electronic inertial overcurrent release with a current-dependent time delay;
Leakage current release;
Minimum voltage actuator;
Reverse current or reverse power release;
Independent release (remote switch off).
The first two types are installed in all three poles, the rest - one per switch. The set currents, as well as the time delays of the current releases, can be adjustable. One or more types of current releases and, in addition to them, an undervoltage release, an independent release and a switching electromagnet can be used in one circuit breaker.
In terms of response time, electromagnetic and similar electronic releases have four types:
Releases that ensure the operation of the circuit breaker in a time much less than 0.01 s, and the switching off of the short-circuit current before it reaches its impact value. Such AVs are called current-limiting.
Releases that provide disconnection of the short-circuit current during the first passage of the current through the zero value tc = 0.01 s.
Unregulated releases, the response time of which exceeds 0.01 s;
Releases with an adjustable time delay (0.1-0.7 s), which allow for slow operation relative to other circuit breakers in the same network, are called selective.
Leakage current releases are used to quickly disconnect sections of the network in which, due to insulation failure or people touching the conductors, a leakage current to the ground has occurred. In this case, the release setting current is selected in the range from 10 to 30 mA, and the voltage dependence time is selected in the range from 10 to 100 ms. This protection is now considered more effective in protecting people from electric shock.
Minimum voltage releases are used to disconnect power sources when they stop supplying the network (early ATS)_, as well as to disconnect electrical receivers, the self-starting of which when the voltage is automatically restored is undesirable. The release voltage is selected in the range from 0.8 to 0.9 Un, the response time is in accordance with the requirements of automatic network power restoration systems.
Independent releases are used for local remote and automatic shutdown of circuit breakers when external protective devices are triggered.
Reverse current or reverse power releases are used to protect generators operating in the electrical system from synchronous failure.
17. Overcurrent directional protection (principle of operation, circuit diagram, calculation of time delays).
Directional current protection of MTNZ line
T 1 > t → 2 > t 3
I p = I` short I p = I` short
U p = U in U p = U in
φ p = 180 - φ a φ p = φ a t 4 > t ← 3 > t 2
I p = I`` short I p = I` short
U p = U in U p = U in
φ p = φ a φ p = 180 - φ a
Switches Q1 - Q3 have directional overcurrent protection. It differs from conventional MTZ in that an additional element is introduced that determines the direction of the short-circuit power - a power direction relay, which reacts to the phase of the short-circuit current relative to the voltage on the substation buses at the installation site of the protection kit, then the “-” power sign and the power direction relay blocks the set protection. If the direction of the short circuit power is from the busbars to the line, then this is the “+” sign of the short circuit power and the power direction relay, closing its contacts, allows the MTNZ set to operate.
As a result of the action of directional protection, sets 2 and 3 do not need to be coordinated, because they are decoupled using the directional action of a relay. This page violates copyright
In order for all equipment in your home or workplace to be protected from electrical surges, you need to install special circuit breakers. They will be able to detect a surge and quickly react to it by disconnecting the entire system from the electricity supply. A person cannot do this on his own, but a certain type of machine can do it in a few seconds.
Types of machines
Device sensitivity
Before you get acquainted with the types of machines, you need to find out with what sensitivity the devices are suitable for home use, and which ones will be inappropriate. This indicator will indicate how quickly the device will respond to a power surge. It has several markings:
Classification of machines
There are different types of machines in relation to the type of current, rated voltage or current indicator and other technical characteristics. Therefore, you need to specifically understand each point separately.
Current type
In relation to this characteristic, machines are divided into:
- For operation on AC power;
- For operation in a DC network;
- Universal models.
Everything is clear here and no additional explanation is needed.
Based on rated current
The value of this characteristic will determine in the network what maximum value the circuit breaker can operate with. There are devices that can operate from 1 A to 100 A and more. The minimum value with which machines can be found on sale is 0.5 A.
Rated voltage indicator
This characteristic indicates what voltage this type of circuit breaker can operate with. Some can operate on a network with a voltage of 220 or 380 Volts - these are the most common options for domestic use. But there are machines that will cope well with higher rates.
By ability to limit the flow of electricity
According to this characteristic, the following are distinguished:
Other characteristics
The number of poles can be from one to four. Accordingly, they are called single-pole, double-pole, and so on.
Automatic machines by number of poles
By structure they are distinguished:
Based on the discharge speed, high-speed, normal and selective devices are produced. They can have a time delay function that can be inversely dependent on the current or independent of it. The time delay may not be set.
Automatic machines also have a drive, which can be manual, connected to a motor or a spring. Switches differ in the presence of free contacts and in the method of connecting conductors.
An important characteristic will be protection from environmental influences. Here we can highlight:
- IP protection;
- From mechanical impact;
- Current conductivity of the material.
All characteristics can be combined in various combinations. It all depends on the model and manufacturer.
Switch types
The machine inside contains a release, which, using a lever, latch, spring or rocker, can instantly disconnect the network from the supply of electricity. Types of circuit breakers are distinguished by the type of release. There are:
Circuit breakers are much more cost effective than fuses. This is because after cooling, the machine can already be turned on, and it will work as it should if the cause of the overload is eliminated. The fuse needs to be replaced. It may not be available and replacing it may take a long time.
Hello friends. The topic of the post is the types and types of circuit breakers (automatic circuit breakers, AB). I also want the results of the crossword puzzle tournament.
Types of machines:
Can be divided into AC, DC and universal switches operating at any current.
Design - there are air, modular, in a molded case.
Rated current indicator. The minimum operating current of a modular machine is 0.5 Ampere, for example. I’ll write soon about how to choose the right rated current for a circuit breaker, subscribe to the blog news so you don’t miss it.
Voltage rating is another difference. In most cases, AVs operate in networks with a voltage of 220 or 380 Volts.
There are current-limiting and non-current-limiting.
All switch models are classified by the number of poles. They are divided into single-pole, double-pole, three-pole and four-pole circuit breakers.
Types of releases - maximum current release, independent release, minimum or zero voltage release.
Speed of operation of circuit breakers. There are high-speed, normal and selective automatic machines. They are available with or without a time delay, independent or inversely dependent on the current response time delay. Characteristics can be combined.
They differ in the degree of protection from the environment - IP, mechanical influences, conductivity of the material. By type of drive - manual, motor, spring.
By the presence of free contacts and the method of connecting conductors.
Types of machines:
What does type AB mean?
Automatic circuit breakers contain two types of circuit breakers - thermal and magnetic.
Magnetic quick-release switch is designed for short-circuit protection. The tripping of the circuit breaker can occur in a time from 0.005 to several seconds.
The thermal breaker is much slower, designed to protect against overload. It works using a bimetallic plate that heats up when the circuit is overloaded. Response time ranges from a few seconds to minutes.
The combined response characteristic depends on the type of connected load.
There are several types of AV shutdown. They are also called types of time-current shutdown characteristics.
A, B, C, D, K, Z.
A– used for breaking circuits with long electrical wiring, serves as good protection for semiconductor devices. They operate at 2-3 rated currents.
B– for general purpose lighting network. They operate at 3-5 rated currents.
C– lighting circuits, electrical installations with moderate starting currents. These can be motors, transformers. The overload capacity of the magnetic circuit breaker is higher than that of type B switches. They operate at 5-10 rated currents.
D– used in circuits with active-inductive loads. For electric motors with high starting currents, for example. At 10-20 rated currents.
K– inductive loads.
Z– for electronic devices.
It is better to look at the data on the operation of switches of types K, Z in the tables specifically for each manufacturer.
That seems to be all, if there is anything to add, leave a comment.
