Free Single-Line Diagram Maker
Describe your electrical power system and get a professional single-line diagram in seconds. No account, no software, no cost.
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A single-line diagram (also called a one-line diagram) is the essential power system drawing for any electrical installation. It uses a single line to represent all three phases of an AC system, showing how power flows from the source through transformers, switchgear, and distribution equipment to loads. Our free single-line diagram maker converts a plain-language description into a properly structured SLD following IEEE 315 and IEC 60617 conventions — no electrical CAD software required.
How to make a single-line diagram in 4 steps
Describe your electrical system
Type a description of your power system — name the sources (utility, generator, solar), voltage levels, transformers, switchgear, and major loads. Include voltage ratings and equipment tags where known for a more accurate diagram.
Generate the diagram
Click Generate and the AI creates a single-line diagram using standard IEEE 315 / IEC 60617 symbols for transformers, breakers, fuses, switches, bus bars, and loads. Voltage levels and equipment tags are annotated automatically.
Review the power flow
Verify the source-to-load path is correct, check that ATS (automatic transfer switch) connections show the normal and alternate supply correctly, and confirm that bus bar voltage ratings match your system design.
Export and use
Download your SLD for permit applications, facility documentation, inspection submittals, or engineering design review. No account or software installation required.
What is a single-line diagram?
A single-line diagram is the primary schematic for electrical power distribution systems. Unlike a full three-phase wiring diagram, an SLD uses one line to represent all conductors of a polyphase circuit, keeping the drawing clear and focused on the system topology — how sources, transformers, protection devices, and loads interconnect. Every electrical engineer, facility manager, and electrical contractor works with SLDs for design, commissioning, and ongoing maintenance.
SLDs follow IEEE Standard 315 (Graphic Symbols for Electrical and Electronics Diagrams) in North America and IEC 60617 internationally. The symbols convey a precise meaning: a transformer winding configuration tells you the grounding scheme, a breaker symbol with a relay indicates a protective relay function, and an ATS shows which source is normal and which is standby. Voltage levels are annotated at each bus, and equipment tags (e.g. TR-1, MCC-A, ATS-1) link the diagram to the equipment schedule.
Power distribution SLDs typically start at the utility point of delivery (metering), pass through a main transformer, and fan out through switchboards and distribution panels to end loads. Mission-critical facilities add redundancy paths — dual utility feeds, uninterruptible power supplies (UPS), and standby generators with automatic transfer switches — all of which must be clearly shown on the SLD to support commissioning and emergency response.
Our free SLD generator is designed for electrical engineers, facility managers, and electrical contractors who need a clear power system drawing quickly. Describe your system in plain language and receive a properly structured single-line diagram that can serve as a starting point for detailed design or as a reference document for facility staff.
Frequently asked questions
What is a single-line diagram used for?
Single-line diagrams are used for electrical system design, permit and inspection submittals, facility documentation, load flow studies, short-circuit analysis, and emergency response reference. They are required for most commercial and industrial electrical installations by the National Electrical Code (NEC) and local authorities having jurisdiction (AHJ).
What is the difference between a single-line diagram and a schematic diagram?
A single-line diagram shows the overall topology of a power system — sources, transformers, protection devices, and loads — using one line per circuit for clarity. A schematic diagram shows every conductor, terminal, and connection in full detail, used for wiring and troubleshooting. SLDs are used for system planning and documentation; schematics are used for installation and field work.
What does an ATS do in a single-line diagram?
An ATS (automatic transfer switch) is shown on an SLD as the point where two sources — typically a utility feed and a standby generator — connect to a load bus. When the normal source (utility) fails, the ATS automatically transfers the load to the alternate source (generator) within a defined transfer time. The SLD shows both the normal and alternate supply paths into the ATS.
What standards govern single-line diagram symbols?
IEEE Standard 315 governs graphic symbols for electrical and electronics diagrams in North America. IEC 60617 is the international equivalent. Both standards define symbols for transformers, circuit breakers, fuses, disconnect switches, motors, generators, and other equipment. Most North American engineering practices follow IEEE 315 for power SLDs.
Can I use this tool for permit drawings?
The generated SLD is a strong starting point for permit packages. For submittals to an authority having jurisdiction (AHJ), the drawing typically must be stamped by a licensed electrical engineer and drawn in a format the AHJ accepts. Use the output from this tool to develop your design quickly, then have a licensed professional engineer review and stamp it for submission.
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