Voltage Rise Calculator AS/NZS 3008
Voltage rise calculator for solar applications in Australia and New Zealand.
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See Also
Parameters
- Installation: Select a predefined installation type.
- Phase: Select 3 Phase AC or 1 Phase AC.
- Voltage (Vac): Select a standard voltage, or select "Other" to specify a custom voltage.
- Specify voltage (Vac): When "Voltage" is selected as "Other", specify a custom voltage value.
- Inverter 1 rating: (A, kVA or kW) Rating of the inverter. When kW is selected, a power factor of 1 is assumed.
- Inverter 2 rating (A, kVA or kW): Rating of the inverter. When kW is selected, a power factor of 1 is assumed.
- Max. voltage rise (%): The maximum allowable voltage rise at the inverter terminals. A limit of 2% is specified by AS/NZS 4777.1-2024. Select from the list of standard percentages or select "Other" to specify a custom value.
- Specify max. voltage rise (%): When "Max. voltage rise" is selected as "Other", enter a custom value.
- Export limit: Select whether the export is limited or not. See Export limit calculation.
- Export limit: Specify the export limit in kW. Assume a power factor of 1. See Export limit calculation.
- Cable size type: Select Single-core or Multi-core.
- Conductor: Select the conductor material: Copper or Aluminium.
- Size (mm2): Select a cable size.
The minimum allowable sizes are:
- Consumer mains, single-phase: 10 mm2
- Consumer mains, three-phase: 6 mm2.
- Parallel cables: 4 mm2.
- Cables: Enter the number of parallel cables.
- Distance (m): Enter the cable distance.
Voltage rise calculation
The voltage rise is calculated from the resistance and reactance data in AS/NZS 3008-2025 (Australian conditions).
Single-phase voltage rise
The single-phase voltage rise per cable is calculated as:
\(\Delta V_{1\phi}=\dfrac{I \cdot L \cdot 2 \cdot Z_{c}}{1000 \cdot m}\)
Where,
- I is the cable current in amperes (A).
- L is the cable distance in meters (m).
- Zc is the cable impedance in Ω/km.
- m is the number of parallel cables.
The percentage voltage rise for single-phase is calculated as:
\(\%\Delta V=\dfrac{\Delta V_{1\phi}}{V_{1\phi}} \cdot 100\)
Where,
- \(\Delta V_{1\phi}\) is the single-phase voltage rise in volt (V).
- \(V_{1\phi}\) is the nominal single-phase voltage in volt (V).
Three-phase voltage rise
The three-phase voltage rise per cable is calculated as:
\(\Delta V_{3\phi}=\dfrac{I \cdot L \cdot \sqrt{3} \cdot Z_{c}}{1000 \cdot m}\)
Where,
- I is the cable current in amperes (A).
- L is the cable distance in meters (m).
- Zc is the cable impedance in Ω/km.
- m is the number of parallel cables.
The percentage voltage rise for three-phase is calculated as:
\(\%\Delta V=\dfrac{\Delta V_{3\phi}}{V_{3\phi}} \cdot 100\)
Where,
- \(\Delta V_{3\phi}\) is the three-phase voltage rise in volt (V).
- \(V_{3\phi}\) is the nominal three-phase voltage in volt (V).
Cable impedance calculation
The cable impedance Zc for the worst-case power factor is calculated as:
\(Z_c = \sqrt{R_c^2 + X_c^2}\)
Where,
- Rc is the cable resistance in Ω/km.
- Xc is the cable reactance in Ω/km.
Cable resistance
The cable resistance values are from AS/NZS 3008-2025 (Australian conditions), Table 4.5(A) (single-core) and Table 4.7(A) (multi-core).
Cable insulation is assumed to be PVC V-90, with a maximum operating temperature of 75°C.
Only copper cables are currently supported.
Cable reactance
Reactance values are from AS/NZS 3008-2025 (Australian conditions), Table 4.1(A) (single-core) and Table 4.1(B) (multi-core).
A flat formation is assumed for single-core cables, which gives the worst-case reactance.
Export limit calculation
The export limit is the maximum power that may be exported to the grid.
It is applied at the Main Switchboard (MSB), i.e. the consumer mains cable between the Point of Supply (POS) and the Main Switchboard (MSB).
If the inverter rating exceeds the export limit, the current in the consumer mains cable is calculated based on the export limit. The current in the other cables is not limited, because the full inverter rating may be consumed by appliances in the installation.
A power factor of 1 is assumed for the export limit.
Other assumptions
The current ratings of the cables are not checked.