For 3-phase 4-wire systems with non-linear loads (LEDs, VSDs, rectifiers), the neutral can carry triple-N harmonics (150 Hz in 50 Hz systems). AS/NZS 3008.1.1 Appendix C (informative) gives a method:
Alternating voltages up to and including 0.6/1 kV.
Cables must be sized to withstand the thermal effects of short-circuit currents (fault currents) for the time it takes the protective device (circuit breaker/fuse) to operate. The standard provides equations and tables to verify that the conductor temperature does not exceed the insulation's limits (e.g., PVC is typically $160^\circ\textC$ during a fault, whereas XLPE can handle $250^\circ\textC$). as/nzs 3008
Selecting the wrong cable size isn't just an administrative error; it's a significant safety and efficiency risk. Proper application of AS/NZS 3008 ensures:
Unlike air, ground temperature varies by depth and season. AS/NZS 3008 defines three soil scenarios: For 3-phase 4-wire systems with non-linear loads (LEDs,
AS/NZS 3008 recognises two standard insulation temperature limits:
If you need the actual tables or a worked example for a specific scenario (e.g., 50 mm² XLPE buried in clay, 30 m run, 3 circuits), let me know. The standard provides equations and tables to verify
If you only remember three things: