EleCAD: Single Line Diagram Software for Professional Electrical Engineers

EleCAD: designing full electrical networks on a single line diagram

Single line diagram software for professional engineers

EleCAD is a free, browser-based single line diagram (SLD) builder for Australian and New Zealand electrical design. You place sources, main switchboards, distribution boards, protective devices, cables and loads from a drag-and-drop palette, and the tool draws the diagram in Australian electrical drawing conventions. There is nothing to install and no licence to manage: the builder runs in any modern desktop browser.

Unlike a generic diagramming tool, every element is an electrical object. A cable is not just a line: it is a conductor with material, insulation, cores and an installation method. A distribution board tracks its incomer and outgoing ways; a protective device records its type, trip curve and breaking capacity; a load carries kW and power factor. That is what lets the diagram drive calculations instead of merely documenting them.

The unit of work is the whole network, not the single circuit. A calculator answers one question about one run; EleCAD holds the point of supply, every board below it, every submain and final subcircuit between them, the embedded generation, the correction plant and the standby supply as one connected system, and solves them together. Demand aggregates up the tree, fault level and loop impedance accumulate down it, and a change at one board reaches every circuit it affects. That is the difference between drawing a design and designing one, and it is why the output is suitable for issued documentation rather than only for concept work.

The diagram stays live as the design changes

Change a downstream load and the upstream maximum demand updates. Change a cable run and the voltage drop, fault level and earth loop impedance all follow. Because the model knows the electrical relationships between components, edits propagate the way they do in the real design, which keeps the SLD, the calculations and the documentation in step through design development.

Every board reports not just its own voltage drop but the worst voltage drop anywhere in the tree below it, so the circuit that will fail the check is visible from the switchboard rather than found by opening each final subcircuit in turn.

What EleCAD checks on every circuit as you draw

These are not checks you run at the end. Each one is recomputed on every edit, and any failure appears in the issue list against the circuit it belongs to, with the change that resolves it.

Parallel cable sets, earth conductors and multi-section switchboards

Real submains are often more than one cable. EleCAD runs any circuit as multiple parallel sets, and the parallel count is carried through the physics rather than bolted on for display: active impedance, voltage drop, voltage rise and the earth fault loop are each divided across the runs. The earth conductor carries its own parallel count when it is not integral to the cable set, and can be sized automatically or fixed manually with an upper bound.

Switchboards are modelled as more than a single bus. A board can carry several busbar sections, tied together into sub-bus groups where the design calls for it, each with its own rating, incoming protection, RCD arrangement, connector device and spare pole allowance. Sections flagged as essential services enforce 110°C elastomeric insulation on the cables feeding them, so a fire-rated requirement cannot be lost between the diagram and the cable schedule.

Protective devices from a real catalogue, not a symbol library

Each protective device on the diagram is backed by a catalogue record from Schneider Electric or NHP, selectable per project. That record carries the trip characteristic the checks depend on: MCB curve B, C or D, the thermal or electronic trip settings on an MCCB or ACB, and the rated breaking capacity. It is why the earth fault loop check can be run against the trip current of the device actually specified rather than a generic assumption, and why breaking capacity can be tested against the fault level at that point in the network.

Auto design closes the loop between the cable and the device. Sizing a cable changes the fault level and loop impedance, which changes which device is acceptable, which in turn changes the current the cable must carry: EleCAD iterates the two together until they agree, subject to a global cap on auto-selected cable size that you set on the source.

Arc flash: an IEEE 1584 study the diagram already has the inputs for

Every three-phase switchboard on the diagram carries an IEEE 1584-2018 incident energy study: bolted fault current, arcing current, clearing time, incident energy in cal/cm² at the working distance, the arc flash boundary and the PPE band that follows. Nothing extra has to be entered for it. The board already knows its own fault level from the network solve, the system voltage from the point of supply, and the upstream device from the incoming cable.

The clearing time is the reason this belongs on the diagram rather than in a standalone calculator. It is the input that makes an arc flash study slow: you find the arcing current, then read the upstream device curve at it by hand. EleCAD knows which device is fitted and what its trip settings are, so it reads the curve itself, at the arcing current rather than at the bolted fault current, and it evaluates both the average and the reduced arcing-current scenarios and takes the worse of the two, as IEEE 1584-2018 requires: a lower arcing current sits further left on the device curve and can clear far more slowly.

What the diagram genuinely cannot know is the physical equipment, so electrode configuration, conductor gap, working distance and enclosure size come from an IEEE 1584 equipment preset, defaulted by the board's role in the network and editable per board. Inputs that fall outside the model's validity range are flagged rather than quietly returned. The study exports as a schedule and as printable equipment labels, each carrying the worse of the mains and standby cases. It supports, and does not replace, a documented arc flash risk assessment and PPE program.

Standby supply: the same installation, solved again on the generator

A standby generator is not a symbol in EleCAD, it is a second operating case. Add a generator, choose an automatic transfer switch (ATS) or a manual changeover (MTS), and mark the busbar sections it backs, and the whole installation is solved a second time with the alternator as the point of supply, carrying its own short-circuit contribution and earth loop impedance.

This matters because a site fed from a 500 kVA transformer and the same site fed from a 125 kVA alternator have fault levels that differ by a factor of five, and the low one is the one that decides whether a breaker still clears an earth fault in time. Designing to the mains figure alone passes every check and leaves the installation unprotected for exactly the hours it is running on the set. The two results are held separately so the generator's far lower fault level can never be mistaken for the utility's, and the arc flash study ranks each board on the worse of the two supplies.

The set is sized from the demand of the sections it backs, through the same engine as the ElecAS Generator Sizing calculator, and the changeover, the standby lead and the backed sections are drawn, scheduled and exported with the rest of the network.

Power factor correction and grid protection

A power factor correction bank sits on a board's busbar as a shunt capacitor. It asks for a target power factor and nothing else: the load kW and the existing power factor are read off the board's own calculated demand, and the reactive-power maths runs through the same engine as the standalone ElecAS Power Factor Correction calculator, returning the required kVAr, the standard bank step, the resulting kVA and current reduction and the capacitance. The bank is demand-neutral upstream, because it supplies reactive power rather than drawing it, but its own feeder and protective device are still sized for the full capacitor design current.

Grid protection is placed for you. Once total PV and battery inverter output on the site passes 30 kW, a DNSP generally requires central grid protection instead of relying on each inverter's own AS/NZS 4777.2 protection: a relay sensing the mains through a CT and tripping a contactor in every inverter supply, so all generation disconnects on a grid fault. EleCAD lands the CT and relay on the main switchboard incoming chain and a contactor on each inverter feeder, carries them through the canvas, legend, schedules and both exports, and removes them again if the site drops back under the threshold. Confirm the required relay settings and any different threshold against your own DNSP connection requirements.

Importing an existing drawing instead of redrawing it

Much of the work on a real project starts from a drawing that already exists: an as-built, a tender sheet, a PDF from another consultant. EleCAD can read one. Upload a PDF or a scanned single line diagram and the SLD reader extracts the switchboards, feeders, protective devices and loads from the sheet.

Nothing reaches the canvas unreviewed, deliberately: a mis-assigned feeder produces a network that verifies cleanly and silently checks the wrong cable, which is worse than an import that fails outright. The review step shows what was read, where each item came from on the drawing, a confidence score against each, and every gap the drawing left behind. The two things a drawing can rarely tell you, run lengths and what a load actually draws, are editable there, and the import is built from your corrected version rather than from the raw reading.

Once it lands, it is an ordinary EleCAD model: cable sizing, voltage drop, fault levels, earth fault loop impedance, arc flash and maximum demand all run on it exactly as they do on a diagram drawn from scratch. That makes it a fast route into checking an existing installation, or into taking over a design someone else started.

Export: PDF for submissions, CSV for schedules, DXF for the drafting team

Diagrams export to a clean branded PDF for tender packages, design submissions and client review, carrying the diagram, title block, legend, compliance summary and the cable, voltage drop, voltage rise, load, circuit breaker, switch and isolator, arc flash, grid protection, power factor correction and standby supply schedules, plus printable arc flash equipment labels. The cable, voltage drop, phase load and arc flash schedules also export as CSV, so a schedule drops straight into a spreadsheet or a switchboard build sheet.

The DXF export carries fully editable CAD geometry with layers, symbols, cables and labels intact. It opens directly in AutoCAD, Revit and BricsCAD, so a drafting team can drop the SLD straight into their sheets without redrawing it. Both exports are free and require only a free account to download.