The neutral wire of a low-voltage four-conductor cable mainly serves the following functions:
Protective grounding: The neutral line can be used as a protective grounding to ensure the safety of electrical equipment and personnel.
Passing through three-phase unbalanced current: In a three-phase four-wire system, the neutral wire is responsible for passing through three-phase unbalanced current. When the three-phase load is unbalanced, there will be current flowing on the neutral wire to balance the current of the entire system.
Preventing power supply voltage changes: The neutral line also plays a role in ensuring that the load phase voltage remains constant, preventing power supply voltage changes due to asymmetric loads, thereby ensuring the normal operation of equipment or preventing equipment damage.
Improving the current-carrying capacity of cables: In a three-phase four-wire system, using a four-core cable can improve the current-carrying capacity of the cable. This is because the neutral wire of the four-core cable has sufficient cross-sectional area to carry unbalanced currents and single-phase load currents without causing the cable to overheat or reduce its current-carrying capacity.
It should be noted that in practical applications, it is not allowed to use a three-core cable with an additional conductor as the neutral line laying method. This will cause three-phase unbalanced currents to pass through the armor of the three-core cable, resulting in cable heating and reducing the current carrying capacity of the cable. Therefore, in the design and construction process, the role and requirements of the neutral line should be fully considered to ensure the safe, stable and efficient operation of the power system.
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