Electrical design from strings to SLD

Preset-driven stringing

PVX.AI defines stringing as the series connections, the positive and negative cable paths, that link modules together before any inverter or transformer sits downstream. Stringing is preset-driven: you build a reusable preset once, then apply it across racks instead of wiring each table by hand. Three stringing types cover the common layouts, plus a custom option for the rest:

Building a preset in the Stringing Setup window sets the direction (Left to Right or Right to Left, toward the transformer or inverter side) alongside the module parameters (Vmpp, Voc, Impp, Power) and the inverter or system parameters (Max System Voltage, default 1500 V; Inverter Vmax, default 1100 V). PVX.AI shows the resulting string size and valid range live as you adjust these values, for example a string size of 26 modules within a range of 24 to 30, or you can set modules per string manually. Each preset also picks an application mode: Single Rack, String Area (every compatible rack in a boundary), or String Frames (selected racks), and every preset is rack-type-aware, remembering which rack spec it applies to.

Once a preset exists, applying it is a two-click choice: Apply to Boundary strings every matching rack inside a selected PV Area, and Apply to Selection strings only the racks you pick. If a string needs correcting afterward, three tools in the Stringing Setup window handle it: Destring removes selected strings, Mirror Strings reverses the positive and negative direction (correctly, even on rotated or tracker racks and locked layers), and Reverse Polarity swaps the polarity of selected strings. Custom Pattern opens the Custom Stringing Editor for line or leapfrog connections spanning two different table types, with draggable string poles and module indices shown for precision.

• Single Row: a straight string path along a single row.
• U-Stringing: a single continuous path that folds back within a table, best for small single-row tables.
• Leap Frog: the string alternates between upper and lower module rows in a zigzag, suited to longer tables.
• Custom: manually define positive and negative connection points across two different table types in the Custom Stringing Editor.

Automatic device placement and cabling

Place Devices offers two modes. Auto (cloud) places transformers, inverters, and DC combiner boxes automatically, snapping transformers to road edges, and cabling then runs on its own right after. Manual hands you the placement and the trench and cable assignment yourself. Either way, PVX.AI color-codes each DC Box group and labels the whole hierarchy, transformer to inverter to DC box to string, from the naming prefixes you set in Configure. If you move a placed transformer afterward, PVX.AI restores the racks it was hiding at the old spot and re-hides racks under the new one, and PVXAI_REFRESHTRAFOFOOTPRINTS re-runs that cleanup across every transformer on demand.

In Auto mode, cabling runs automatically after placement, and moving a device prompts a re-cabling pass so cables detour around the new position; Regenerate Cabling re-runs the cloud cabling against current devices and strings whenever you need to. In Manual mode, you build the routing yourself: Generate Trenches from Roads lays cable trenches along the service roads, then Assign DC Trench and Assign AC Trench pick a transformer and its trench polylines. Generate Selection routes DC and AC cables for one transformer at a time; Generate All routes every transformer in the design in one pass.

Either mode sizes cables to meet a voltage-drop target rather than a fixed gauge: you set the standard (IEC or NEC), the conductor (copper or aluminum), a target voltage-drop percentage, and the system voltage, and PVX.AI works out the rest. The output reports the resulting cross-sections, cable lengths, total cable power, and voltage-drop percentage per group, so an oversized or undersized run shows up immediately instead of after the cable order goes out. On one 30 MWp design, PVX.Cad verified voltage drop across all 2,165 strings and completed the electrical workflow in 1 to 2 days, compared with 3 to 4 weeks classically. Read the full 30 MWp electrical design case study.

See the whole system: overview and SLD

Electrical Design, then Information, then Overview opens the Electrical Overview window, a bird's-eye tree of the whole design: transformers in light blue, inverters in green, DC combiner boxes in orange, and strings in grey. Expand All, Collapse All, Refresh, and Export controls manage the tree itself, and right-clicking any node gives you Locate Object, Hide/Show Object, Change Parent Device, or Delete, so you can restructure the hierarchy without redoing the electrical design. The same Information dropdown holds a Cable Information Table, and once devices are placed, the drawing itself is color-coded by substation zone, inverter, or DC combiner, whichever level you want to inspect.

Generate SLD, on the Electrical Design panel, turns a completed design into an IEC-60617 single line diagram on its own PVXAI_SLD paper-space layout tab, so it never clutters the model-space drawing. Choose Aggregated to collapse identical inverters into a single times-N row for a printable sheet, or Full Detail to draw every inverter individually for data verification. DC wiring draws in orange, AC in green, and MV in red, and a title band summarizes the plant: total MW and the transformer, inverter, and string counts.

You need a completed electrical design, transformers placed, before generating an SLD, and if the string count the diagram would draw does not match the design, PVX.AI aborts the generation without touching any existing SLD tab, so a stale diagram is never silently overwritten with a broken one. When battery storage is part of the site, the SLD also includes the BESS and PCS clusters with their MW and MWh totals, so storage and generation appear on the same sheet.