Selection of Cable Core for Voltage Levels of 1kV and Below
2026-05-30
In long-distance lines or high-current circuits, single-core cables are recommended to reduce intermediate joints and save costs. Furthermore, single-core cables are also suitable for low-voltage DC power supply circuits.
At voltage levels of 1kV and below, if the power supply neutral point is directly grounded and the protective conductor and neutral conductor share the same conductor in a single-phase circuit, a 2-core cable should be selected. For DC power supply circuits, a 2-core cable is also recommended. Of course, depending on specific grounding and current requirements, 3-core and 4-core cables are also available.
4-core cables (3+1 structure) for 1kV and below not only use the fourth core for protective grounding but also bear the important task of transmitting unbalanced current and short-circuit current in the power system. Their specifications need to be determined based on the actual requirements of unbalanced current and short-circuit current, but generally should not be less than 1/2 of the phase conductor's current carrying capacity. In low-voltage power distribution systems of 1kV and below, if a three-phase four-wire system is used, and the protective earth (PE) and neutral (PN) conductors share the same conductor, a 4-core cable must be selected to avoid power frequency interference problems caused by non-standard configurations.
For electrical installations with extremely high safety requirements, and for communication centers and automation equipment that require simultaneous electrical safety and interference-resistant grounding, a 5-core TN-C low-voltage power distribution system is recommended. This allows the protective earth (PE) and neutral (PN) conductors to operate independently, with their core cross-sectional areas typically being 3 large and 2 small, 4 large and 1 small, or 5 large, ensuring independent PE and PN conductors and providing reliable grounding and interference immunity.
