Ouzo designation on a single-line diagram. Symbol for ouzo in the diagram
An example of RCD calculation.
RCD designation.
RCD connection diagram.
Connect to the terminal L phase, to N
RCD diagram in the apartment.
Rice. 1 RCD diagram in the apartment.
Installing an RCD significantly increases the level of safety when working on electrical installations. If the RCD has high sensitivity (30 mA), then it provides protection against direct contact (touch).
However, installing an RCD does not mean taking the usual precautions when working on electrical installations.
The test button must be pressed regularly, at least once every 6 months. If the test does not work, then you need to think about replacing the RCD, since the level of electrical safety has decreased.
Install the RCD on the panel or housing. Connect the equipment exactly according to the diagram. Turn on all loads connected to the protected network.
The RCD is triggered.
If the RCD trips, find out which device is causing the trip by sequentially disconnecting the load (we turn off the electrical equipment one by one and see the result). If such a device is detected, it must be disconnected from the network and checked. If the electrical line is very long, the normal leakage currents can be quite high. In this case, there is a possibility of false positives. To avoid this, it is necessary to divide the system into at least two circuits, each of which will be protected by its own RCD. You can calculate the length of the electrical line.
If it is impossible to determine in a documentary way the sum of leakage currents of wiring and loads, you can use an approximate calculation (in accordance with SP 31-110-2003), taking the load leakage current equal to 0.4 mA per 1 A of power consumed by the load and the leakage current of the electrical network equal to 10 μA per meter length of the phase wire of the electrical wiring.
An example of RCD calculation.
For example, let’s calculate an RCD for an electric stove with a power of 5 kW, installed in the kitchen of a small apartment.
The approximate distance from the panel to the kitchen can be 11 meters, respectively, the estimated wiring leakage is 0.11 mA. An electric stove, at full power, consumes (approximately) 22.7A and has a calculated leakage current of 9.1mA. Thus, the sum of the leakage currents of this electrical installation is 9.21 mA. To protect against leakage currents, you can use an RCD with a leakage current rating of 27.63 mA, which is rounded to the nearest higher value of the existing differential ratings. current, namely RCD 30mA.
The next step is to determine the operating current of the RCD. With the maximum current consumed by the electric stove indicated above, you can use the nominal value (with a small margin) of a 25A RCD, or with a larger margin - a 32A RCD.
Thus, we calculated the rating of the RCD that can be used to protect the electric stove: RCD 25A 30mA or RCD 32A 30mA. (you must remember to protect the RCD with a 25A circuit breaker for the first rating of the RCD and 25A or 32A for the second rating).
RCD designation.
In the diagram, the RCD is designated as follows: Fig. 1 single-phase RCD, fig. 2 - three-phase RCD.
RCD connection diagram.
Let's look at the RCD connection diagram using an example. On the picture. Figure 1 shows a fragment of a distribution cabinet.
Photo. 1 Connection diagram for a three-phase RCD with a circuit breaker (in the photo, number 1 RCD, 2 - circuit breaker) and single-phase RCD (3).
The RCD does not protect against short-circuit currents, so it is installed in conjunction with a circuit breaker. What to install before the RCD or circuit breaker is not important in this case. The rating of the RCD should be equal to or slightly greater than the rating of the circuit breaker. For example, a circuit breaker is 16 Amperes, which means we set the RCD to 16 or 25 A.
As you can see in the photo. 1, three phase and neutral conductors are suitable for a three-phase RCD (number 1), and after the RCD a circuit breaker is connected (number 2). The consumer will connect: phase conductors (red arrows) from the circuit breaker; neutral conductor (blue arrow) - with RCD.
Number 3 in the photo shows differential machines connected by a busbar, the operating principle of the differential. the machine is the same as that of an RCD, but it additionally protects against short-circuit currents and does not require additional short-circuit protection.
And the connection is that of the RCD, that of the differential. machines are the same.
Connect to the terminal L phase, to N zero (designations are marked on the body of the RCD). Consumers are also connected.
RCD diagram in the apartment.
Below is a diagram of using an RCD in an apartment for additional protection against electric shock.
Rice. 1 RCD diagram in the apartment.
In this case, the RCD is installed before the meter, on the entire group of circuit breakers, which provides additional protection against electric shock and fire.
Installing an RCD significantly increases the level of safety when working on electrical installations. If the RCD has high sensitivity (30 mA), then it provides protection against direct contact (touch).
However, installing an RCD does not mean taking the usual precautions when working on electrical installations.
The test button must be pressed regularly, at least once every 6 months. If the test does not work, then you need to think about replacing the RCD, since the level of electrical safety has decreased.
Install the RCD on the panel or housing. Connect the equipment exactly according to the diagram. Turn on all loads connected to the protected network.
The RCD is triggered.
If the RCD trips, find out which device is causing the trip by sequentially disconnecting the load (we turn off the electrical equipment one by one and see the result).
Learning to distinguish an RCD from a differential circuit breaker - 4 external signs
If such a device is detected, it must be disconnected from the network and checked. If the electrical line is very long, the normal leakage currents can be quite high. In this case, there is a possibility of false positives. To avoid this, it is necessary to divide the system into at least two circuits, each of which will be protected by its own RCD. You can calculate the length of the electrical line.
If it is impossible to determine in a documentary way the sum of leakage currents of wiring and loads, you can use an approximate calculation (in accordance with SP 31-110-2003), taking the load leakage current equal to 0.4 mA per 1 A of power consumed by the load and the leakage current of the electrical network equal to 10 μA per meter length of the phase wire of the electrical wiring.
An example of RCD calculation.
For example, let’s calculate an RCD for an electric stove with a power of 5 kW, installed in the kitchen of a small apartment.
The approximate distance from the panel to the kitchen can be 11 meters, respectively, the estimated wiring leakage is 0.11 mA. An electric stove, at full power, consumes (approximately) 22.7A and has a calculated leakage current of 9.1mA. Thus, the sum of the leakage currents of this electrical installation is 9.21 mA. To protect against leakage currents, you can use an RCD with a leakage current rating of 27.63 mA, which is rounded to the nearest higher value of the existing differential ratings. current, namely RCD 30mA.
The next step is to determine the operating current of the RCD. With the maximum current consumed by the electric stove indicated above, you can use the nominal value (with a small margin) of a 25A RCD, or with a larger margin - a 32A RCD.
Thus, we calculated the rating of the RCD that can be used to protect the electric stove: RCD 25A 30mA or RCD 32A 30mA. (you must remember to protect the RCD with a 25A circuit breaker for the first rating of the RCD and 25A or 32A for the second rating).
RCD designation.
In the diagram, the RCD is designated as follows: Fig. 1 single-phase RCD, fig. 2 - three-phase RCD.
RCD connection diagram.
Let's look at the RCD connection diagram using an example. On the picture. Figure 1 shows a fragment of a distribution cabinet.
Photo. 1 Connection diagram for a three-phase RCD with a circuit breaker (in the photo, number 1 RCD, 2 - circuit breaker) and single-phase RCD (3).
The RCD does not protect against short-circuit currents, so it is installed in conjunction with a circuit breaker. What to install before the RCD or circuit breaker is not important in this case. The rating of the RCD should be equal to or slightly greater than the rating of the circuit breaker. For example, a circuit breaker is 16 Amperes, which means we set the RCD to 16 or 25 A.
As you can see in the photo. 1, three phase and neutral conductors are suitable for a three-phase RCD (number 1), and after the RCD a circuit breaker is connected (number 2). The consumer will connect: phase conductors (red arrows) from the circuit breaker; neutral conductor (blue arrow) - with RCD.
Number 3 in the photo shows differential machines connected by a busbar, the operating principle of the differential. the machine is the same as that of an RCD, but it additionally protects against short-circuit currents and does not require additional short-circuit protection.
And the connection is that of the RCD, that of the differential. machines are the same.
Connect to the terminal L phase, to N zero (designations are marked on the body of the RCD). Consumers are also connected.
RCD diagram in the apartment.
Below is a diagram of using an RCD in an apartment for additional protection against electric shock.
Rice. 1 RCD diagram in the apartment.
In this case, the RCD is installed before the meter, on the entire group of circuit breakers, which provides additional protection against electric shock and fire.
Uzo designation on the GOST diagram
Very often, inexperienced electricians and home craftsmen do not know how to determine what is in the panel - an RCD or a circuit breaker. As a result, one may mistakenly think that the electrical wiring is protected from overloads and current leakage, although in fact, protection is not provided against the first unsafe situation, because The panel contains a conventional residual current device. In this article we will not only look at the functional difference between these two devices, but also tell you how to visually distinguish an RCD from a difavtomat.
- Differences in Functions
- Visual difference
Differences in Functions
Let us briefly describe how a residual current device differs from a differential circuit breaker. It's quite simple:
This is the main functional difference between the two devices. You can find out whether it is better to install an RCD or a difavtomat in our corresponding article. Now we will tell you how to distinguish them by appearance.
Visual difference
Now, using photo examples, we will clearly show how to determine what exactly is installed in the panel. In total, we will tell you about 4 obvious signs that you need to remember.
The diagram of the differential circuit breaker will additionally indicate a thermal and electromagnetic release, which are absent on the diagram of the differential switch. This difference is also significant when determining the device.
Main Differences
So we have provided instructions for young electricians and home craftsmen. As you can see, in fact there is nothing complicated, and the difference between a residual current device and a differential circuit breaker is quite significant. We hope you now know how to visually distinguish an RCD from a difavtomat!
If for an ordinary person the perception of information occurs by reading words and letters, then for mechanics and installers they are replaced by alphabetic, digital or graphic symbols. The difficulty is that while the electrician completes his training, gets a job, and learns something in practice, new SNiPs and GOSTs appear, according to which adjustments are made. Therefore, you should not try to learn all the documentation at once. It is enough to gain basic knowledge and add relevant data as you work.
Introduction
For circuit designers, instrumentation mechanics, electricians, the ability to read an electrical diagram is a key quality and indicator of qualification. Without special knowledge, it is impossible to immediately understand the intricacies of designing devices, circuits and methods of connecting electrical units.
Types and types of electrical circuits
Before you begin to study the existing symbols of electrical equipment and its connections, you need to understand the typology of circuits. On the territory of our country, standardization has been introduced according to GOST 2.701-2008 dated July 1, 2009, according to “ESKD. Scheme. Types and types. General requirements".
Based on this standard, all schemes are divided into 8 types:
- United.
- Located.
- Are common.
- Connections.
- Installation connections.
- Completely principled.
- Functional.
- Structural.
- Combined.
- Divisions.
- Energy.
- Optical.
- Vacuum.
- Kinematic.
- Gas.
- Pneumatic.
- Hydraulic.
- Electrical.
Among the existing 10 species indicated in this document, the following are distinguished:
For electricians, it is of greatest interest among all the above types and types of circuits, as well as the most popular and often used in work - an electrical circuit.
The latest GOST, which came out, has been supplemented with many new designations, current today with code 2.702-2011 dated January 1, 2012. The document is called “ESKD. Rules for the execution of electrical circuits” refers to other GOSTs, including the one mentioned above.
The text of the standard sets out clear requirements in detail for electrical circuits of all types. Therefore, when performing installation work with electrical circuits, this document should be used as a guide. The definition of the concept of an electrical circuit, according to GOST 2.702-2011, is as follows:
“An electrical diagram should be understood as a document containing symbols of parts of a product and/or individual parts with a description of the relationship between them and the principles of operation from electrical energy.”
Once defined, the document contains rules for the implementation on paper and in software environments of contact connection designations, wire markings, letter designations and graphic representations of electrical elements.
It should be noted that most often only three types of electrical circuits are used in home practice:
- Assembly– for the device, a printed circuit board is shown with the arrangement of elements with a clear indication of the location, rating, principle of fastening and connection to other parts. Electrical wiring diagrams for residential premises indicate the number, location, rating, connection method and other precise instructions for the installation of wires, switches, lamps, sockets, etc.
- Fundamental– they indicate in detail the connections, contacts and characteristics of each element for networks or devices. There are complete and linear circuit diagrams. In the first case, control, control of elements and the power circuit itself are depicted; in a linear diagram, they are limited only to the circuit with the remaining elements depicted on separate sheets.
- Functional– here, without detailing the physical dimensions and other parameters, the main components of the device or circuit are indicated. Any part can be depicted as a block with a letter designation, supplemented by connections with other elements of the device.
Graphic symbols in electrical diagrams
The documentation, which specifies the rules and methods for graphically designating circuit elements, is represented by three GOSTs:
- 2.755-87 – graphic symbols of contact and switching connections.
- 2.721-74 – graphic symbols of parts and assemblies for general use.
- 2.709-89 – graphic symbols in electrical diagrams of sections of circuits, equipment, contact connections of wires, electrical elements.
In the standard with code 2.755-87, it is used for diagrams of single-line electrical panels, conventional graphic images (CGI) of thermal relays, contactors, switches, circuit breakers, and other switching equipment. There is no designation in the standards for automatic devices and RCDs.
On the pages of GOST 2.702-2011 it is allowed to depict these elements in any order, with explanations, decoding of the UGO and the circuit diagram of the difavtomat and RCD itself.
GOST 2.721-74 contains UGOs used for secondary electrical circuits.
IMPORTANT: To designate switching equipment there is:
4 basic UGO images
9 functional signs of UGO
| UGO | Name |
| Arc suppression | |
| No self-return | |
| With self-return | |
| Limit or travel switch | |
| With automatic operation | |
| Switch-disconnector | |
| Disconnector | |
| Switch | |
| Contactor |
IMPORTANT: Designations 1 – 3 and 6 – 9 are applied to the fixed contacts, 4 and 5 are placed on the moving contacts.
Basic UGO for single-line diagrams of electrical panels
| UGO | Name |
| Thermal relay | |
| Contactor contact | |
| Switch - load switch | |
| Automatic - circuit breaker | |
| Fuse | |
| Differential circuit breaker | |
| RCD | |
| Voltage transformer | |
| Current transformer | |
| Switch (load switch) with fuse | |
| Motor protection circuit breaker (with built-in thermal relay) | |
| A frequency converter | |
| Electricity meter | |
| Normally closed contact with reset button or other push-button switch, with reset and opening by means of a special actuator of the control element | |
| Normally closed contact with push-button switch, with reset and opening by retracting the control button | |
| Normally closed contact with push-button switch, with reset and opening by repeated pressing of the control button | |
| Normally closed contact with push-button switch, with automatic reset and opening of the control element | |
| Delayed closing contact that initiates upon return and operation | |
| Delayed closing contact which is only initiated when triggered | |
| Delayed closing contact which is actuated by return and tripping | |
| Delayed closing contact which only operates on return | |
| Delayed closing contact that only switches when triggered | |
| Timing relay coil | |
| Photo relay coil | |
| Pulse relay coil | |
| General designation of a relay coil or contactor coil | |
| Indication lamp (light), lighting | |
| Motor drive | |
| Terminal (separable connection) | |
| Varistor, surge arrester (surge suppressor) | |
| Arrester | |
Socket (plug connection):
|
|
| A heating element |
Designation of measuring electrical instruments to characterize circuit parameters
GOST 2.271-74 accepts the following designations in electrical panels for buses and wires:
Letter designations in electrical diagrams
The standards for the letter designation of elements on electrical circuits are described in the GOST 2.710-81 standard with the text title “ESKD. Alphanumeric designations in electrical circuits." The mark for automatic devices and RCDs is not indicated here, which is prescribed in clause 2.2.12 of this standard as a designation with multi-letter codes. The following letter codings are accepted for the main elements of electrical panels:
| Name | Designation |
| Automatic switch in the power circuit | QF |
| Automatic switch in the control circuit | SF |
| Automatic switch with differential protection or difavtomat | QFD |
| Switch or load switch | QS |
| RCD (residual current device) | QSD |
| Contactor | K.M. |
| Thermal relay | F, KK |
| Timing relay | KT |
| Voltage relay | KV |
| Impulse relay | KI |
| Photo relay | KL |
| Surge arrester, arrester | F.V. |
| fuse | F.U. |
| Voltage transformer | TV |
| Current transformer | T.A. |
| A frequency converter | UZ |
| Ammeter | PA |
| Wattmeter | PW |
| Frequency meter | PF |
| Voltmeter | PV |
| Active energy meter | P.I. |
| Reactive energy meter | P.K. |
| Heating element | E.K. |
| Photocell | B.L. |
| Lighting lamp | EL |
| Light bulb or light indicating device | H.L. |
| Plug or socket connector | XS |
| Switch or circuit breaker in control circuits | S.A. |
| Push-button switch in control circuits | S.B. |
| Terminals | XT |
Representation of electrical equipment on plans
Despite the fact that GOST 2.702-2011 and GOST 2.701-2008 take into account this type of electrical circuit as a “layout diagram” for the design of structures and buildings, one must be guided by the standards of GOST 21.210-2014, which indicate “SPDS.
Images on the plans of conventional graphic wiring and electrical equipment.” The document establishes UGO on plans for laying electrical networks of electrical equipment (lamps, switches, sockets, electrical panels, transformers), cable lines, busbars, tires.
The use of these symbols is used to draw up drawings of electric lighting, power electrical equipment, power supply and other plans. The use of these designations is also used in basic single-line diagrams of electrical panels.
Conventional graphic images of electrical equipment, electrical devices and electrical receivers
The contours of all depicted devices, depending on the information richness and complexity of the configuration, are taken in accordance with GOST 2.302 on the scale of the drawing according to the actual dimensions.
Conventional graphic designations of wiring lines and conductors
Conventional graphic images of tires and busbars
IMPORTANT: The design position of the busbar must exactly coincide on the diagram with the place of its attachment.
Conventional graphic images of boxes, cabinets, panels and consoles
Conventional graphic symbols of switches, switches
On the pages of documentation GOST 21.210-2014 there is no separate designation for push-button switches, dimmers (dimmers). In some schemes, according to clause 4.7. the normative act uses arbitrary designations.
Conventional graphic symbols of plug sockets
Conventional graphic symbols of lamps and spotlights
The updated version of GOST contains images of lamps with fluorescent and LED lamps.
Conventional graphic symbols of monitoring and control devices
Conclusion
The given graphic and letter images of electrical components and electrical circuits are not a complete list, since the standards contain many special signs and codes that are practically not used in everyday life. To read electrical diagrams, you will need to take into account many factors, first of all, the country of manufacture of the device or electrical equipment, wiring and cables. There is a difference in markings and symbols on the diagrams, which can be quite confusing.
Secondly, you should carefully consider areas such as intersections or lack of a common network for wires located with the overlay. On foreign diagrams, if a bus or cable does not have a common power supply with intersecting objects, a semicircular continuation is drawn at the point of contact. This is not used in domestic schemes.
If a diagram is depicted without complying with the standards established by GOSTs, then it is called a sketch. But for this category there are also certain requirements, according to which, based on the sketch provided, an approximate understanding of the future electrical wiring or design of the device should be drawn up. Drawings can be used to create more accurate drawings and diagrams based on them, with the necessary symbols, markings and compliance with scales.
Differential automatic machines (difavtomats) are designed on the principle of combining two protective functions in one device and have the capabilities of an automatic circuit breaker (AB) and an RCD. As automatic devices, they protect power lines from overloads and short circuits (short circuits), and as RCDs, they protect a person from electric shock. The second protective function of these devices is explained by their ability to respond to the slightest leakage of electricity to the ground caused by a violation of the insulation of conductive parts or the touch of a living creature to them.
The built-in RCD circuit of a differential circuit breaker operates on the principle of comparing current components flowing in the forward and reverse branches of the controlled circuit. If the balance of these quantities is disturbed (the appearance of a current differential), the difference signal is sent to the executive relay, which instantly disconnects the dangerous section from the power line. What are the characteristics of difavtomats?
Operating current and speed
The design features of difavtomats are the reason that they have combined characteristics used in describing the operation of both AV and RCD. The main operating characteristic of these electrical products is the rated operating current, at which the device can remain turned on for a long time.
This characteristic of the device refers to strictly standardized indicators, as a result of which the current can only take values from a certain series (6, 10, 16, 25, 50 Amperes, and so on).
In addition, the designation of devices uses a current indicator associated with the speed, denoted by the numbers “B”, “C” or “D”, standing in front of the rated current value.
Speed is an important current and time characteristic. The designation C16, for example, corresponds to a circuit breaker with a “C” time characteristic, designed for a nominal value of 16 Amps.
Trip current and voltage
The group of technical characteristics of the difavtomat includes the circuit shutdown current (differential indicator), defined as the “current leakage setting”. For most models, the permissible values of this characteristic fall into the following series: 10, 30, 100, 300 and 500 milliamps. On the body of the difavtomat it is indicated by the “delta” icon with a number corresponding to the leakage current.
Another characteristic of the operational capabilities of difavtomats is the rated voltage at which they are able to operate for a long time (220 Volts for a single-phase network and 380 Volts for three-phase circuits). The operating voltage of the protective differential device can be indicated under the rating designation with a letter or under the switch key.
Leakage current and selectivity
The next characteristic by which all difavtomats differ is the type of leakage current. In accordance with this parameter, any of the automatic machines can have the following designations:
- “A” – responsive to leaks of sinusoidal alternating (pulsating direct) current;
- “AC” – automatic devices designed to be triggered by leaks containing a constant component;
- “B” is a combined design that offers both of the previously mentioned options.
The characteristic “type of built-in RCD” is marked with a letter index or a small picture.
By analogy with RCDs, difavtomats can operate on a selective principle, which assumes a delay in response time. This feature ensures a certain selectivity in disconnecting the device from the network and the electrodynamic stability of the protection system. According to this characteristic, differential devices are marked with the symbol “S”, which means a delay of the order of 200-300 milliseconds, or are marked with the sign “G” (60-80 milliseconds).
Basic designations
We will consider in more detail the order of labeling of a difavtomat (location of its characteristics) using the example of a domestic product of the “AVDT32” brand, used in protection circuits for industrial and household electrical networks.
For the convenience of systematizing the information presented, a graphic designation will be understood as a certain marking position.
The first position indicates the name and series of the automatic machine. From this designation it follows that it is a differential type AV with built-in protection against dangerous leakage currents. The difavtomat is intended for use in single-phase alternating current electrical networks with a rated voltage of 230 Volts (50 Hertz).
In the place corresponding to position No. 3 (above), such a characteristic as the value of the rated differential short-circuit current is indicated.
Note! Sometimes in this place you can see the value of the maximum switching capacity of the device, indicating the value of the maximum current at which the automatic circuit breaker can be turned off many times.
At the same position, but below, there is a graphic designation of the type of built-in circuit breaker (in this case it is type “A”, designed to work with leakages of pulsating direct and sinusoidal alternating currents).
In place of the 4th position you can see a modular one, which indicates the elements included in its composition that are involved in the implementation of protective functions. For RCBO32 in this diagram the following modules and assemblies are indicated by symbols:
- electromagnetic and thermal releases that provide protection of lines from short-circuit currents and overloads, respectively;
- a special “Test” button, necessary for manually checking the serviceability of the machine;
- amplification electronic module;
- executive unit (relay line switching).
At position number seven, the speed-related characteristic of the emergency operation of the electromagnetic release is indicated in the first place (for our example, this is “C”). Immediately followed by the rated current indicator, indicating the value of this parameter in operating mode (over a long time).
The minimum shutdown (trigger) current of an electromagnetic type release for a difavtomat with characteristic “C” is usually taken equal to approximately five rated currents. With this current characteristic value, the thermal release operates in approximately 1.5 seconds.
In the eighth position there is usually a “delta” icon with an indicator of the rated leakage current, which turns off the differential device in case of danger. These are all the basic electrical characteristics.
Information signs
The fifth position shows the temperature characteristics of the protective device (from - 25 to + 40 degrees), and the sixth position contains two signs.
One of them informs the user about the certificate of conformity, that is, it indicates the current domestic GOST for the difavtomat (GOST R129 - for this case).
Directly below it is a characteristic encoded in the form of letters and numbers. This is the designation of the organization that issued the certificate.
Important! This sign informs the consumer about the legal origin of the product and its quality and, if necessary, ensures the legal protection of the device.
To the right of it are the certification and GOST data for this model regarding its fire safety.
And finally, in the place corresponding to the second position, the logo of the manufacturer’s trademark (in this case, “IEC”) is applied.
Dimensions and connection points
The main overall characteristics of the difavtomat according to GOST are its height, width and thickness, as well as the size of the height and width of the shelf with the control button protruding from the front side. In addition, the dimensions of the shelves located on the back side are given, limiting the gap for mounting the device on the DIN rail that secures it.
Modern models of difavtomat can have one or another size, each of which can be found in the documentation attached to this product. But in most cases, the dimensional characteristics are similar, which simplifies placement in the shield.
Regarding the contact points for connecting this device to the protected circuit, the following should be noted. In a single-phase network, differential devices are installed that have two input and two output contacts. One of these groups is used to connect the so-called “phase” wire, and the “zero” power conductor is connected to the other. As a rule, all contacts (upper and lower) are marked with the symbols “L” and “N”, indicating, respectively, the places where the phase and zero are connected.
When the device is connected to the electrical circuit, the phase and neutral wires coming from the input distribution device or electric meter are connected to the upper contacts. Its lower terminals are intended for switching conductors going directly to the protected load (to the consumer).
Connecting a differential device to three-phase power circuits is completely similar to the previously discussed option. The only difference in this case is that three phases are connected to the automatic machine at once: “A”, “B” and “C”. By analogy with the case of a single-phase 220 Volt power line, the terminals of a three-phase difavtomat are also marked (in order to maintain phasing) and designated as “L1”, “L2”, “L3” and “N”.
Competent selection of a device suitable for the stated purposes is impossible without carefully studying the main operating characteristics of the difavtomat and the corresponding markings. In this regard, before purchasing a differential device, try to carefully study all the material presented in this article.
Reading diagrams is impossible without knowledge of the conventional graphic and letter designations of the elements. Most of them are standardized and described in regulatory documents. Most of them were published in the last century, and only one new standard was adopted, in 2011 (GOST 2-702-2011 ESKD. Rules for the execution of electrical circuits), so sometimes a new element base is designated according to the principle “as who came up with it.” And this is the difficulty of reading circuit diagrams of new devices. But, basically, the symbols in electrical circuits are described and are well known to many.
Two types of symbols are often used on diagrams: graphic and alphabetic, and denominations are also often indicated. From this data, many can immediately tell how the scheme works. This skill is developed over years of practice, and first you need to understand and remember the symbols in electrical circuits. Then, knowing the operation of each element, you can imagine the final result of the device.
Drawing and reading different diagrams usually require different elements. There are many types of circuits, but in electrical engineering the following are usually used:
There are many other types of electrical circuits, but they are not used in home practice. The exception is the route of cables passing through the site and the supply of electricity to the house. This type of document will definitely be needed and useful, but it is more of a plan than an outline.
Basic images and functional features
Switching devices (switches, contactors, etc.) are built on contacts of various mechanics. There are make, break and switch contacts. The normally open contact is open; when it is switched to operating state, the circuit is closed. The break contact is normally closed, but under certain conditions it operates, breaking the circuit.
The switching contact can be two or three position. In the first case, first one circuit works, then another. The second one has a neutral position.
In addition, contacts can perform different functions: contactor, disconnector, switch, etc. All of them also have a symbol and are applied to the corresponding contacts. There are functions that are performed only by moving contacts. They are shown in the photo below.
Basic functions can only be performed by fixed contacts.
Symbols for single line diagrams
As has already been said, single-line diagrams indicate only the power part: RCDs, automatic devices, automatic circuit breakers, sockets, circuit breakers, switches, etc. and connections between them. The designations of these conventional elements can be used in electrical panel diagrams.
The main feature of graphic symbols in electrical circuits is that devices similar in principle of operation differ in some small detail. For example, a machine (circuit breaker) and a switch differ only in two small details - the presence/absence of a rectangle on the contact and the shape of the icon on the fixed contact, which display the functions of these contacts. The only difference between a contactor and a switch designation is the shape of the icon on the fixed contact. It's a very small difference, but the device and its functions are different. You need to look closely at all these little things and remember them.
There is also a small difference between the symbols of the RCD and the differential circuit breaker. It also only functions as moving and fixed contacts.
The situation is approximately the same with relay and contactor coils. They look like a rectangle with small graphic additions.
In this case, it’s easier to remember, since there are quite serious differences in the appearance of the additional icons. With a photo relay it’s so simple - the rays of the sun are associated with the arrows. A pulse relay is also quite easy to distinguish by the characteristic shape of the sign.
A little easier with lamps and connections. They have different “pictures”. A detachable connection (such as a socket/plug or socket/plug) looks like two brackets, and a detachable connection (such as a terminal block) looks like circles. Moreover, the number of pairs of checkmarks or circles indicates the number of wires.
Image of tires and wires
In any circuit there are connections and for the most part they are made by wires. Some connections are buses - more powerful conductor elements from which taps can extend. Wires are indicated by a thin line, and branches/connections are indicated by dots. If there are no points, it is not a connection, but an intersection (without an electrical connection).
There are separate images for buses, but they are used if they need to be graphically separated from communication lines, wires and cables.
On wiring diagrams it is often necessary to indicate not only how the cable or wire runs, but also its characteristics or installation method. All this is also displayed graphically. This is also necessary information for reading drawings.
How switches, switches, sockets are depicted
There are no standards-approved images for some types of this equipment. So, dimmers (light regulators) and push-button switches remained without designation.
But all other types of switches have their own symbols in electrical diagrams. They come in open and hidden installations, respectively, there are also two groups of icons. The difference is the position of the line on the key image. In order to understand in the diagram what type of switch we are talking about, this must be remembered.
There are separate designations for two-key and three-key switches. In the documentation they are called “twin” and “twin”, respectively. There are differences for cases with different degrees of protection. In rooms with normal operating conditions, switches with IP20, maybe up to IP23, are installed. In wet rooms (bathroom, swimming pool) or outdoors, the degree of protection should be at least IP44. Their images differ in that the circles are filled in. So it's easy to distinguish them.
There are separate images for the switches. These are switches that allow you to control turning the light on/off from two points (there are also three, but without standard images).
The same trend is observed in the designations of sockets and socket groups: there are single, double sockets, and there are groups of several pieces. Products for rooms with normal operating conditions (IP from 20 to 23) have an unpainted middle; for wet rooms with a housing of increased protection (IP44 and higher), the middle is tinted dark.
Symbols in electrical diagrams: sockets of different types of installation (open, hidden)
Having understood the logic of the designation and remembering some initial data (what is the difference between the symbolic image of an open and hidden installation socket, for example), after a while you will be able to confidently navigate the drawings and diagrams.
Lamps on diagrams
This section describes the symbols in the electrical circuits of various lamps and fixtures. Here the situation with the designations of the new element base is better: there are even signs for LED lamps and fixtures, compact fluorescent lamps (housekeepers). It’s also good that the images of lamps of different types differ significantly - it’s difficult to confuse them. For example, lamps with incandescent lamps are depicted in the form of a circle, with long linear fluorescent lamps - a long narrow rectangle. The difference in the image of a linear fluorescent lamp and an LED one is not very big - only dashes at the ends - but even here you can remember.
The standard even includes symbols in electrical diagrams for ceiling and pendant lamps (socket). They also have a rather unusual shape - circles of small diameter with dashes. In general, this section is easier to navigate than others.
Elements of electrical circuit diagrams
Schematic diagrams of devices contain a different element base. Communication lines, terminals, connectors, light bulbs are also depicted, but in addition, there is a large number of radio elements: resistors, capacitors, fuses, diodes, thyristors, LEDs. Most of the symbols in the electrical circuits of this element base are shown in the figures below.
Rarer ones will have to be looked for separately. But most circuits contain these elements.
Letter symbols in electrical diagrams
In addition to graphic images, elements on the diagrams are labeled. It also helps to read the diagrams. Next to the letter designation of an element there is often its serial number. This is done so that later it is easy to find the type and parameters in the specification.
The table above shows international designations. There is also a domestic standard - GOST 7624-55. Excerpts from there with the table below.
No person, no matter how talented and savvy he may be, can learn to understand electrical drawings without first becoming familiar with the symbols that are used in electrical installation at almost every step. Experienced specialists claim that only an electrician who has thoroughly studied and mastered all the generally accepted designations used in project documentation can have a chance to become a true professional in their field.
Greetings to all friends on the website “Electrician in the House”. Today I would like to pay attention to one of the initial issues that all electricians face before installation - this is the design documentation of the facility.
Some compose it themselves, while others are provided by the customer. Among the multitude of this documentation, you can find copies in which there are differences between symbols certain elements. For example, in different projects the same switching device can be graphically displayed differently. Has this ever happened?
It is clear that it is impossible to discuss the designation of all elements within one article, so the topic of this lesson will be narrowed, and today we will discuss and consider how ouzo designation on the diagram .
Every novice master must carefully familiarize himself with generally accepted GOSTs and the rules for marking electrical elements and equipment on plan diagrams and drawings. Many users may disagree with me, arguing that why do I need to know GOST, I’m just installing sockets and switches in apartments. Design engineers and university professors should know the schemes.
I assure you this is not so. Any self-respecting specialist must not only understand and be able to read electrical circuits. but also must know how various communication devices, protective devices, metering devices, sockets and switches are graphically displayed on diagrams. In general, actively use project documentation in your daily work.
Uzo designation on a single-line diagram
The main groups of RCD designations (graphic and alphabetic) are used very often by electricians. The work of drawing up work diagrams, schedules and plans requires very great care and accuracy, since a single inaccurate indication or mark can lead to a serious error in further work and cause the failure of expensive equipment.
In addition, incorrect data can mislead third-party specialists hired for electrical installations and cause difficulties when installing electrical communications.
Currently, any ouzo designation on a diagram can be represented in two ways: graphically and alphabetically.
Which regulatory documents should be referred to?
Of the main documents for electrical diagrams that refer to the graphic and letter designation of switching devices, the following can be distinguished:
- — GOST 2.755-87 ESKD “Conventional graphic designations in electrical circuits of devices, switching and contact connections”;
- — GOST 2.710-81 ESKD “Alphanumeric designations in electrical circuits.”
Graphic designation of RCD on the diagram
So, above I presented the main documents according to which symbols in electrical circuits are regulated. What do these GOST standards give us for studying our question? I'm ashamed to admit, but absolutely nothing. The fact is that today these documents do not contain information on how the ouzo designation should be carried out on a single-line diagram.
The current GOST does not have any special requirements for the rules of preparation and use. RCD graphic symbols doesn't put forward. That is why some electricians prefer to use their own sets of values and labels to mark certain components and devices, each of which may differ slightly from the values we are familiar with.
As an example, let's look at what designations are printed on the body of the devices themselves. Hager residual current device:
Or for example an RCD from Schneider Electric:
To avoid confusion, I suggest that you jointly develop a universal version of RCD designations that can be used as a guide in almost any working situation.
In terms of its functional purpose, a residual current device can be described as follows: it is a switch that, during normal operation, is capable of turning on/off its contacts and automatically opening the contacts when a leakage current appears. Leakage current is a differential current that occurs during abnormal operation of an electrical installation. Which organ reacts to differential current? A special sensor is a zero-sequence current transformer.
If we present all of the above in graphical form, it turns out that RCD symbol on the diagram can be represented in the form of two secondary designations - a switch and a sensor responding to differential current (zero-sequence current transformer) which affects the contact disconnection mechanism.
In this case graphic designation of ouzo on a single-line diagram will look like this.
How is the difavtomat indicated on the diagram?
About designations of difavtomats in GOST At the moment there is also no data. But, based on the above diagram, the difavtomat can also be graphically represented in the form of two elements - an RCD and a circuit breaker. In this case, the graphic designation of the difavtomat on the diagram will look like this.
Letter designation of ouzo on electrical diagrams
Any element on electrical circuits is assigned not only a graphic designation, but also an alphabetic designation indicating a position number. This standard is regulated by GOST 2.710-81 “Alphanumeric designations in electrical circuits” and is mandatory for application to all elements in electrical circuits.
So, for example, according to GOST 2.710-81, it is customary to designate circuit breakers using a special alphanumeric designation in this way: QF1, QF2, QF3, etc. Switches (disconnectors) are designated as QS1, QS2, QS3, etc. Fuses in the diagrams are designated as FU with the corresponding serial number.
Similarly, as with graphic symbols, GOST 2.710-81 does not contain specific data on how to perform alphanumeric designation of RCDs and differential circuit breakers on the diagrams .
What to do in this case? In this case, many masters use two notation options.
The first option is to use the most convenient alphanumeric designation Q1 (for RCD) and QF1 (for RCBO), which indicate the functions of the switches and indicate the serial number of the device located in the circuit.
That is, the encoding of the letter Q means “switch or switch in power circuits,” which may well be applicable to the designation of an RCD.
The code combination QF stands for Q – “switch or switch in power circuits”, F – “protective”, which may well be applicable not only to conventional machines, but also to differential machines.
The second option is to use the alphanumeric combination Q1D for the RCD and the combination QF1D for the differential circuit breaker. According to Appendix 2 of Table 1 of GOST 2.710, the functional meaning of the letter D means “differentiating”.
I very often saw in real diagrams the following designation: QD1 - for residual current devices, QFD1 - for differential circuit breakers.
What conclusions can be drawn from the above?
Due to the fact that there is no designation for RCDs and differential circuit breakers according to GOST, the information discussed in this article does not apply to mandatory regulatory documents, but is only a RECOMMENDATION. Each designer can depict these elements on the diagrams at his own discretion. To do this, you just need to provide conventional graphic designations (UGO) of the elements, their decoding and explanations for the diagram. All these actions are provided for in GOST 2.702-2011.
How is ouzo indicated on a single-line diagram - an example of a real project
As the famous proverb says, “it’s better to see once than to hear a hundred times,” so let’s look at a real example.
Let's assume that we have a single-line diagram of the power supply of an apartment. From all these graphic symbols, the following can be distinguished:
The input residual current device is located immediately after the meter. By the way, as you may have noticed, the letter designation of the RCD is QD. Another example of how ouzo is designated:
Please note that on the diagram, in addition to the UGO elements, their marking is also applied, that is: type of device by type of current (A, AC), rated current, differential leakage current, number of poles. Next we move on to UGO and marking of differential machines:
The socket lines in the diagram are connected through differential circuit breakers. Letter designation of the difavtomat on the diagram QFD1, QFD2, QFD3, etc.
One more example How are differential automatic machines designated on a single-line diagram? store
That's all, dear friends. This concludes our lesson today. I hope this article was useful to you and you found the answer to your question here. If you have any questions, ask them in the comments, I will be happy to answer. Let's share our experience, who denotes RCDs and RCBOs in diagrams. I would be grateful for a repost on social networks))).
