When designing an electrical distribution system, it’s common practice to use a simplified notation in order to represent the electrical system. This graphical representation is called a single(one) line diagram (SLD).

The single line diagram can represent an entire system or a small part of an electrical circuit. Electrical elements such as circuit breakers, transformers, capacitors, busbars, contactors and conductors are shown by standardized schematic symbols.

Universally accepted electrical symbols are used to represent the different electrical components and their relationship within the circuit. To interpret SLD’s one must be familiar with these symbols. Web sites such as CLA Standards (www.clsstandards.com) have documented these symbols and are easily accessible.

Single line diagrams are often drawn using CAD software such as Autocad. However, these programs are costly and for someone looking for a free program with a full list of components, EDM offers a program called “ElectricalDM”, which can be downloaded (www.electricaldm.com) on a one month free trial period.

The single-line diagram is the blueprint for electrical system analysis. It is the first step in preparing an electricaldesign.A single line allowing you to become thoroughly familiar with any electrical system layout and design.

The single-line diagram also becomes your lifeline of information when updating or responding to an emergency. An accurate diagram ensures optimum system performance and coordination for all future testing or trouble-shootingand can highlight potential risks before a problem occurs.

Understanding and using the single line diagram will make designing proper electrical circuits easier than ever.