what is an electrical diagram and What are the different types of electrical diagrams

What is an electrical diagram

Electrical diagrams are drawings which are used to represent electrical circuits, these circuits are represented by using lines, symbols, and number combinations. Electrical diagrams show the wiring between components and the relative position of the components. With the help of the electrical diagram we could get a better understanding of the electric circuits which are used in buildings. In order to do the electrical wiring in a building electrical diagrams are used and by using this diagram the electrical installation is made by the electricians.

What is the need for an electrical diagram

Electrical diagrams can be used to make new electrical installations and they can be used to locate electrical problems and it will also be helpful to modify the existing circuit. Electrical diagrams are used to troubleshoot the problems and to make sure that all connections are correct.

What are the different types of electrical diagrams

Wiring diagram

A wiring diagram is drawn by using symbols, these symbols represent the devices of an electrical control panel. It shows the wiring between the components the lines represent the wires and they are marked with numbers or letter-number combinations. Wiring diagrams are used by the equipment manufacturers to install wires in electrical equipment such as switchboards and panels. The wiring diagram shows the interconnection wiring between the electrical equipment. These diagrams show the functional device in their correct relative physical locations. Lines are used to representing the single conductors, multiple conductors that are installed in the same channel are shown as a single line with radial branches and the representation of the conductor is labeled with an identifying number.

Single line diagram

It is also known as one line diagram which is mostly used in an industrial power system. Mostly single line diagrams are used to represent the complex power system, these diagrams will show all the electrical components in the power system and their interconnections. Single line diagrams can be used to determine the power system problems it can be useful to determine which circuit interrupters must be opened to safely isolate the electrical apparatus.

Three line diagram

Three line diagrams are used to get the detailed information which is related to three-phase circuitry, which can’t be seen in a single line diagram. These diagrams will be helpful for the plant maintenance and the operation personnel could understand the power system operations very easily. The three-line diagrams use the same symbol as the single line diagram to represent the power system components it also has some additional symbols which are used in schematic and wiring diagrams. These diagrams will show every conductor of a power circuit as an individual line.

Schematics diagram

The schematic diagram uses lines and symbols to show how the parts of an electrical unit are connected. It doesn’t show where the parts are located but with the help of this diagram, we could do the electrical connections. This diagram shows the internal connection and circuit element in an arrangement which will allow the technician to interpret the function and operational logic of an electrical control unit. These diagrams have symbols that are seen in a single line, three-line, and wiring diagrams it will show all terminals and connections of functional devices.

Types of schematic diagram

Internal schematic –This diagram will only show the internal circuits of a single physical device

External schematic diagram – These diagrams will show the internal circuit of the physical device and it will also show the external circuits that conduct input and output signals into and out of the devices.

Ladder diagram

These diagrams are specialized schematics which is commonly used to document industrial control logic systems. These diagrams are most commonly used for understanding and designing system control logic. A ladder diagram is a top-down logical line schematic because it moves from power input at the top through sequential operations. Ladder diagrams are used to draw relay control circuits, ladder diagram is different from the wiring diagram because the ladder diagram is more schematic and shows each branch of the circuit on a separate horizontal row. These diagrams will describe the function of each branch and the resulting operations. Ladder diagrams have two vertical lines the left one is connected to the voltage source and the right one to the ground. In the vertical lines, a set of horizontal rows represents different branches of the control circuit.

Elementary diagrams

These diagrams will show all the operational elements and all of the circuits of a complete electrical control system. It is also used to represent the complete control circuit of an electrical sub-station.

Logic diagram

It shows the logic for complex circuits, processes, or devices it uses block type and standardized logic-function symbols to represent highly complex functions that are performed either by integrating processing modules or by individual devices. These diagrams will be useful to the users to understand the related logic function of the device without the specific knowledge of their internal operations. These diagrams use blocks and logic function symbols to represent complex functions and every block will contain a logic symbol that describes the function of the block. Straight-line represents the path of process control signals. The points were these signal paths enters and leaves the block is the input and output signals of the block.

Riser diagram

Riser diagram is a single line diagram that shows the entire electrical circuit from the service entrance up to the smallest circuit branch. It shows the size of wire in each branch, size of the service entrance conductors and the conduit and size of the protective device for the main circuit breaker and each branch. It got the name riser diagram because it shows the path of wiring or raceways from one level of the building to the other, it won’t show the location of the equipment in a room or area. These diagrams are used because they are easy to understand.


post-graduate in Electronics & communication.

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