One-Line Diagram Builder & Explorer

Build, edit, and explore single-line diagrams using standard power system symbols — with automatic energized-path tracing, load aggregation, connection mapping, and five preset system topologies.

PREVIEWAUTOMATED CHECKS ONLYCONCEPTUAL ONLYINTERMEDIATEWHAT DO THESE STATUSES MEAN?

5 PRESET TOPOLOGIESPATH TRACINGLOAD AGGREGATIONSTANDARD SYMBOLS

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Overview

The one-line diagram is the primary communication tool of power systems engineering, and reading or building one accurately is a foundational skill. This educational builder lets you place and connect standard power system elements — utility sources, transformers, switchgear, circuit breakers, buses, loads, generators, and ATS switches — then immediately see the result of your topology choices. The Explorer tab traces every energized source-to-load path in the diagram and flags blocked paths (open devices or ATS). The Load Aggregation tab sums demand from all connected loads back through the system. An Equipment List and Connection Map provide tabular views of the diagram. Five preset topologies cover Simple Radial, Ring Bus (with one tie open), Industrial Plant, Emergency Power (ATS), and Commercial Building — giving students and engineers a starting point for exploration without building from scratch. Symbol explanations are built in. This is an educational tool for understanding system topology and power flow, not a production drafting tool.

App preview

A live look at the app you'll launch — every control on the left drives the visualizations on the right in real time.

Inside the lab

Example data — not a real field report

Builder tab with a canvas of standard one-line symbols and connections — Builder — the drawing canvas. Drop utility sources, transformers, switchgear, breakers, buses, generators, ATS, and loads, then draw connections between them. Symbols follow standard one-line conventions so what you build here reads like a real SLD.

Explorer tab showing energized source-to-load path tracing — Explorer — traces every energized source-to-load path in the current diagram and flags blocked paths caused by open breakers or ATS in the wrong position. Open a device and watch the downstream loads drop off the energized list in real time.

Load Aggregation tab summing demand back to the source — Load Aggregation — sums individual load demand through every distribution element back to the source, showing total kVA/kW at each bus, transformer, and feeder. Great for teaching how demand rolls up through a system.

Scenarios tab with preset system topologies — Scenarios — five preset topologies (Simple Radial, Ring Bus with a tie open, Industrial Plant, Emergency Power with ATS, Commercial Building) that load a fully wired diagram in one click. Ideal for comparing topology trade-offs without building from scratch.

Learn tab with one-line symbol reference and topology theory — Learn — reference material for reading one-line diagrams: standard symbols, radial vs main-tie-main vs ring-bus topologies, ATS operation, and how the Explorer and Load Aggregation views map to real engineering deliverables.

What you'll do

01Place and connect standard one-line diagram symbols for sources, transformers, breakers, buses, and loads
02Trace energized paths from source to load through a radial, ring-bus, and ATS system topology
03Explain how an open breaker or ATS in transfer position changes the energized path in a system
04Aggregate load demand from individual loads through distribution equipment to the source
05Identify the key differences between simple radial, main-tie-main, and ring-bus topologies
06Read and interpret a one-line diagram connection map and equipment list

Try a guided scenario

Build a small radial system and trace power from source to load.

One-line diagram fundamentals · Electrical Foundations

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What this lab is not

Not a design document, stamped calculation, or approval record.
Not a substitute for engineering analysis by a licensed professional.
Not connected to live equipment and not a safety device.

Calculation basis

Results are computed from first-principles circuit relationships using the values you enter.

Simplifying assumptions are stated in the lab itself; where a model is intentionally conceptual, the lab says so rather than implying study-grade accuracy.

Standards basis: Conceptual only. Validation state: Automated checks only (last checked 2026-08-15).