SLD (Single Line Diagram) Posted on 21st December 201528th May 2022 by ThePD (The Project Definition) A Single Line Diagram (SLD) refers to a One Line Diagram. Related Definitions in the Project: The Electrical Engineering Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Engineering and tagged design basis, diagram, electrical. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.