Cabling and protections
Radiaris pre-sizes the cable cross-sections and the protections, and calculates the real ohmic losses of each circuit instead of applying a fixed 1 %. It is enabled in 6 · Advanced settings → Cabling and protections; if you enable it, it replaces the «DC cabling» of the aggregated losses.
Pre-sizing
The results are a design guide based on the Spanish Low Voltage Regulation (REBT). The final project or technical report must check the real conditions of the installation.
What it calculates
DC side (one cable per string, from the modules to the inverter) - Minimum cross-section that meets the ampacity and the voltage drop. - Hour-by-hour Joule loss: P = I²·R, with I = P_string / V_mpp and R = 2·ρ(T)·L / S. - String fuses when there are 3 or more strings in parallel (criterion of IEC 62548).
AC side (line from the inverter to the distribution board) - Minimum cross-section, design current and circuit breaker. - Loss: single-phase P = I²·2ρL/S (I = P/V); three-phase P = 3·I²·ρL/S (I = P/(√3·V)). - 30 mA type A residual current device on a separate circuit for homes or residential areas. - Protective conductor according to the ITC-BT-19 table.
Regulations applied (REBT, RD 842/2002)
| Aspect | Reference |
|---|---|
| Ampacity (copper, in air, 40 °C; PVC or XLPE/EPR; 2 or 3 conductors) | ITC-BT-19, Table 1 (UNE 20460-5-523) |
| Ambient temperature other than 40 °C | ITC-BT-07, Table 13 |
| Cable grouping | ITC-BT-06, Table 6 |
| Array connection cables: ampacity ≥ 125 % of the array maximum; drop ≤ 1.5 % | ITC-BT-40, section 5 |
| Overload protection: Ib ≤ In ≤ Iz | ITC-BT-22 (UNE 20460-4-43) |
| 30 mA type A residual current device | ITC-BT-40, section 4.3 |
| Protective conductor cross-section | ITC-BT-19, Table 2 |
| Maximum DC voltage | 1,500 V (art. 4 of the Regulation) |
Editable parameters
| Parameter | Default |
|---|---|
| Length of each string to the inverter (one way) | 15 m (you can set one length per plane) |
| Inverter → distribution board length | 10 m |
| Maximum DC drop | 1 % of Vmp |
| Maximum AC drop | 1,5 % |
| DC and AC cross-section | Automatic (the smallest standard size that complies) or fixed |
| Average conductor temperature (losses) | 50 °C |
| AC voltage | 230 V single-phase / 400 V three-phase, depending on the inverter |
| DC: installation method, insulation, ambient temperature | C, XLPE, 60 °C (cables under the modules and in the sun) |
| AC: installation method, insulation, ambient temperature | B, XLPE, 40 °C |
| Grouped circuits | DC: the parallel strings of the MPPT; AC: 1 |
Where to see the result
In 7 · Scenarios and report → Analysis details: table of cross-sections and protections, voltage drop of each circuit and total annual cabling loss. The loss is included in the loss waterfall.
Ohmic losses (calculation)
The resistivity of copper is calculated at the conductor temperature:
ρ(T) = ρ20 · (1 + α · (T − 20))
The DC loss is capped at 10 % of the power as a safeguard against absurd data.