Development of structural and functional diagrams of automatic control

An electrical diagram is a document in which, according to GOST rules, connections between the component parts of devices operating due to the flow of electricity are indicated. As you understand, this drawing gives electricians an understanding of how the installation works and what elements it consists of. The main purpose of the electrical diagram is to help in connecting installations, as well as troubleshooting in the circuit.

First, you need to understand what is meant by types and what is meant by types of documents. So, according to GOST 2.701-84, there are the following types of circuits (brief designation in brackets):

1. Electrical (E).
2. Hydraulic (G).
3. Pneumatic (P).
4. Gas (X).
5. Kinematic (K).
6. Vacuum (B).
7. Optical (L).
8. Energy (P).
9. Divisions (E).
10. Combined (C).

As for the types, the main ones are:

1. Structural (1).
2. Functional (2).
3. Fundamental (complete) (3).
4. Connections (installation) (4).
5. Connections (5).
6. General (6).
7. Location (7).
8. United (8).

Based on the indicated designations, you can understand its type and type by the name of the electrical circuit.

Next, we will consider in detail the purpose and composition of each of the listed types of electrical circuits. Before doing this, we recommend that you familiarize yourself with the standard symbols on the diagrams to make it even easier to understand what each version of the drawing is.

Types of electrical circuits

1.1. Structural scheme

This type of document is the simplest and gives an understanding of how the electrical installation works and what it consists of. A graphical representation of all circuit elements allows you to initially see the overall picture in order to move on to a more complex connection or repair process. The reading order is indicated by arrows and explanatory inscriptions, which allows even a novice electrician to understand the structural electrical diagram. You can see the principle of construction in the example below:

Figure 1 — Block diagram

1.2. Functional diagram

The functional electrical diagram of the installation, in fact, is not too different from the structural one. The only difference is a more detailed description of all the components of the chain. This document looks like this:

Figure 2 - Functional diagram

1.3. Schematic diagram

The electrical circuit diagram is most often used in distribution networks, because gives the most comprehensive explanation of how the electrical equipment in question works. Such a drawing must necessarily indicate all the functional components of the circuit and the type of connection between them. In turn, the circuit diagram can have two varieties: single-line (Figure 3) or complete (Figure 4). In the first case, only primary networks, also called power networks, are shown in the drawing. An example of a single line image can be seen below:

Figure 3 - Single line circuit diagram

A complete circuit diagram can be expanded or elemental. If the electrical installation is simple and all the explanations can be put on one main drawing, it is enough to make a detailed plan. If you are dealing with complex equipment that includes a control, automation and measurement circuit, it is better to separate all the individual components into different sheets so as not to get confused.

Figure 4 - Complete circuit diagram

There is also a schematic diagram of the product. This type of document is a kind of copy from the general plan, which only indicates how a certain unit works and what it consists of.

1.4. Wiring diagram

We most often use this type of electrical diagram when we talk about how to install electrical wiring yourself. The fact is that the wiring diagram can show the exact location of all the elements of the circuit, the method of connecting them, as well as the alphanumeric characteristics of the installations that make up the drawing. If we take Figure 5 as an example of the electrical wiring diagram in a one-room apartment, we will see where we need to place sockets, switches, lamps and other products.

Figure 5 - Wiring diagram

The main purpose of a wiring diagram is to provide a guide for electrical work. According to the prepared drawing, you can understand where, what and how to connect.

1.5. Combined scheme

Well, the last electrical circuit used in distribution networks is the combined Figure 6, which can include several types and types of documents. It is used if it is possible to indicate all the important features of the circuit without too much cluttering of the drawing. The integrated project is used most often in enterprises. Home craftsmen are unlikely to encounter this type of scheme. You can see an example below:

Figure 6 - Integrated scheme

Functions and tasks of the System subsystems

For each subsystem, a list of functions and tasks performed by it is provided. The list of functions and tasks is taken from the section “Requirements for functions performed by the system” of the technical specification.

Subsystem for collecting, processing and loading data

Storage subsystem

Reporting generation and visualization subsystem

Symbols on electrical diagrams

All elements in the diagrams are depicted by conventional graphic symbols, the design and dimensions of which are established in the ESKD standards (GOST 2.721-74 ... GOST 2.796-81).

In diagrams rich in conventional graphic symbols, all symbols are allowed to be proportionally reduced or increased, while the distance (clearance) between two adjacent lines of the conventional graphic symbol must be at least 1.0 mm. Conventional graphic symbols of elements used as components of symbols of other elements can be depicted smaller in comparison with other elements (for example, a resistor in a rhombic antenna).

The distance between individual graphic symbols must be at least 2.0 mm.

Images of elements are drawn on diagrams in the position established by the relevant standard, or rotated at an angle multiple of 90° with respect to this position. In some cases, it is allowed to rotate conventional graphic symbols by an angle that is a multiple of 45°, or depict them as mirror images.

Conventional graphic symbols containing letters and numbers can be rotated counterclockwise only by an angle of 90° or 45°.

Conventional graphic symbols, the ratio of sizes of which are given in the relevant standards on a modular grid, must be depicted on diagrams in dimensions determined vertically and horizontally by the number of steps of the modular grid M.

Figure 7 – Modular grid

In this case, the modular grid step for each circuit can be anything but the same for all elements and devices of a given circuit.

As for the graphic designation of all elements used in the diagram, we will provide this overview in the form of tables in which the products will be grouped by purpose.

In Table 1 you can see how electrical boxes, panels, cabinets and consoles are marked on electrical diagrams:

Table 1 - Designation of boxes, panels, cabinets, consoles

The next thing you should know is the symbol for power sockets and switches (including walk-through ones) on single-line diagrams of apartments and private houses:

Table 2 - Designation of switches, switches and sockets

As for lighting elements, lamps and fixtures according to GOST are indicated as follows:

Table 3 - Images of lamps and spotlights with a combined image on the plan of equipment and electrical networks

In more complex circuits where electric motors are used, elements such as:

Table 4 – Conventional graphic designation of electrical machines

It is also useful to know how transformers and chokes are graphically indicated on circuit diagrams:

Table 5 - Conventionally graphic designation of transformers, autotransformers, chokes

Electrical measuring instruments according to GOST have the following graphic designation on the drawings:

Table 6 - Conventionally graphic designation of some electrical measuring instruments

And here, by the way, is a useful table for novice mechanics and electricians, which shows what the ground loop looks like on the electrical wiring plan, as well as the power line itself:

Table 7 – Electrical communication lines, wires, cables and buses

In addition, in the diagrams you can see a wavy or straight line, “+” and “-”, which indicate the type of current.

Table 8 – Type of current and voltage, types of winding connections, pulse shapes

In more complex automation schemes, you may encounter incomprehensible graphic symbols, such as contact connections. Remember how these devices are designated on electrical diagrams:

Table 9 - Switching devices and contact connections

In addition, you should be aware of what radio elements look like on projects (diodes, resistors, transistors, etc.).

Table 10 – Conventional graphic designation (diodes, resistors, transistors)

Single-line electrical circuits also have their own letters, which make it clear what is included in the network. So, according to GOST 7624-55, the letter designation of elements on electrical circuits is as follows:

1. Relays for current, voltage, power, resistance, time, intermediate, indicating, gas and time-delayed, respectively - RT, RN, RM, RS, RV, RP, RU, RG, RTV.
2. KU – control button.
3. KV – limit switch.
4. CC – command controller.
5. PV – travel switch.
6. DG is the main engine.
7. DO – cooling pump motor.
8. DBH is a high-speed engine.
9. DP – feed motor.
10. DS – spindle motor.

In addition, in the marking of elements of radio engineering and electrical circuits, the following letter designations are distinguished:

Table 11 — Letter designations of elements of radio engineering and electrical circuits

Rules for reading diagrams and working on them

In order to quickly and correctly read electrical diagrams, you need:

1. Know the symbolic graphic designations of elements: capacitors, resistors, inductors, relays, motors, switches, batteries, lamps and others.
2. Be able to mentally separate complex circuits into simple ones, and use additional structural and functional types of circuits. You should study the drawings systematically, in accordance with the logic of the device. If documents contain links to other sources, you should familiarize yourself with them.
3. Studying the operation of the circuit may require constructing diagrams of the interaction of individual sections of the circuit, reflecting the order of operation of telemetry, automation, and protection.

This information will help assess the likelihood of element malfunctions, lack of proper contacts, or false connections.

Detailed diagrams of parts of the functional structure

The section provides a detailed model in IDEF0 , reflecting information connections between the functions of the information system subsystems and their relationship with the external environment.

The purpose of using the IDEF0 is to visually display a detailed level of information data flows between functions within each subsystem and display incoming/outgoing flows of interaction with external elements.

Download: IDEF0_example_DataWarehouse_v1.zip

Kovtun M.V. October 2010