20 Single Line Diagram Symbols you need to know

A Single Line Diagram or SLD is a simple visual representation of three-phase power systems.

In this post you’ll learn what is Single Line Diagram and why do we need it.

Our electrical power systems primarily contain three phases of AC circuits. Transmission, distribution, and power transformers are also three phases. While analyzing these systems, using three lines (all three phases) makes the documentation work complex. For this reason, a single-line diagram is used instead.

Consider the schematic diagram of a three-phase generator that feeds a three-phase motor load:

Let’s redraw the single-line diagram for the above case:

As you can see, the single line diagram is a clean representation of the overall system that provides the big picture of the entire power system. Even for a simple case like above, the SLD is useful, practically SLDs are used for power systems and substations containing thousands of components and devices.

Given below are 20 SLD symbols that components that are most important in Electrical and Electronics Engineering.

Photos adapted from: Lessons In Industrial Instrumentation 2008-2022 by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License Only photos adapted from source. Text and other materials where not mentioned are property of Electrical and Electronics Engineering.com

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