Size every PV cable to UTE C15-712-1, from the one-line diagram
pvSpline sizes each cable of the plant on its one-line diagram: it picks the smallest cross-section that carries the current after derating and keeps the voltage drop within its target, under the electrical code you choose. Every cable you size then feeds its real ohmic loss into the simulation.
Three codes, the French one by default
The Electrical code setting picks the rules: UTE C15-712-1 (FR), NEC (US) or IEC 60364. A project where it was never set follows UTE C15-712-1, the French PV rules, whatever the language of the page. The code sets the ampacity tables, the derating factors, the default voltage-drop targets and the conduit-fill limits. It also heads the bill of materials and decides which of a module’s two maximum system voltages a string is held to: the IEC rating under UTE C15-712-1.
Three checks in one calculation
- Ampacity: the smallest conductor that still carries the design current after the ambient-temperature and grouping derates, and the protection rating when one is set, so the cable cannot overheat before its breaker or fuse trips. A buried run is also derated for the soil’s thermal resistivity.
- Voltage drop: ΔV = k × (I / parallel sets) × (L / 1000) × impedance, with k = 2 for DC and single-phase and k = √3 for three-phase; the cross-section goes up until ΔV is within the target.
- Conduit fill: when a conduit is chosen, its fill ratio is checked against the code’s limit.
When no conductor can satisfy both the ampacity and the voltage drop, the editor says so and stores nothing.
The voltage-drop targets of UTE C15-712-1
Under UTE C15-712-1, pvSpline aims for 1% on a string cable and 2% on the DC trunk, 3% in all on the DC side, and 3% on the AC side from the inverter to the delivery point. Each run takes its role’s target by default, and you can set your own on any run.
Currents and lengths taken from the project
- Auto derives the design current, the voltage, the power factor and the protection rating for the cable’s edge of the diagram. A DC edge uses the modules’ worst-case Isc × 1.25, scaled by the strings feeding it.
- Calculate from plan estimates a DC trunk or an AC circuit from the map: the distance between the pinned equipment, times a routing factor, plus a vertical drop. A string cable’s length is typed, one way, in metres.
- A cable catalogue applies its material and insulation and stamps its part reference on the run; the gauge still comes from the code.
Losses that reach the yield
Every run in the wire schedule feeds its ohmic (I²R) loss into the simulation’s loss cascade, with the combiner resistances and the power-factor setpoints, so a longer or thinner cable shows in the energy at the meter. The one-line diagram and the bill of materials download from the results.
Size a DC string cable in six steps
- On Diagram, click Add wire… under the wire schedule of the Design tab.
- Leave Circuit role on DC string and choose the Diagram edge, for example String → combiner input.
- Click Auto beside Design current: the current, the voltage and the protection come from the project.
- Enter the Length, one way, in metres.
- Click Calculate: the result gives the gauge, the voltage drop against its target and the derated ampacity.
- Click Add to schedule: the run joins the wire schedule, and its loss the simulation.
Questions
Which code does a new project follow?
UTE C15-712-1, the French PV rules, until you pick another in the Diagram settings fold. Choose the code before you size any cable: it changes the tables, the derates and the targets used everywhere downstream.
Does a cable already sized follow a change of code?
It keeps the gauge it was sized with. Open it from the wire schedule, then press Calculate and Update run.
Why does Add to schedule grey out after an edit?
A sizing is valid only for the exact inputs it came from, so any edit clears the result. Press Calculate again and the button comes back.
The fastest way to judge a simulation tool is to run it on a project you already know.