A lighting circuit on a 10 A breaker in New Zealand takes 1.5 mm² copper cable on a typical route. For 30 m of multicore PVC cable enclosed in air at 30 °C, the tool gives 16 A of derated capacity and a voltage drop of 4.3 %.
The case
The circuit is single‑phase at 230 V. The design current is the full 10 A of the curve C breaker. The voltage drop limit is 5 % and Ze is 0.35 Ω. Table 5.1 gives a 1.5 mm² earth, and the earth fault loop impedance is 1.34 Ω.
Voltage drop is the check closest to its limit. A longer run reaches the limit before the cable runs out of capacity.
What changes the answer
A 16 A lighting circuit on the same route takes 2.5 mm² with a drop of 3.76 %.
See also: How far can 1.5 mm² run on a 10 A circuit? and Voltage drop basics.