Why Is the Neutral Current Greater Than the Live Current? (1)
In the daily inspection of the power distribution cabinet, the zero-line current inspection is also an essential process! In the routine electrical inspection of the equipment department, it is sometimes found that the value of the neutral line current exceeds the live line current, and the neutral line heats up seriously. What is the cause? Today, the editor will take you to understand the reason why the neutral current is greater than the live current.
1. Three-phase load imbalance. In a three-phase four-wire power distribution system, if the three-phase loads are identical linear (R/L/C) loads, that is, three-phase balanced, the three-phase currents differ by 120°. In the N line, they cancel each other out, and the current theory in the N line is 0, which is basic common sense. However, when the three-phase load is a non-linear load, such as a rectifier circuit, although the three-phase loads are exactly the same, the current in the N line is not zero, even greater than the phase line current.
Causes of three-phase Unbalance:
(1) Weakening of monitoring efforts for distribution transformer loads. In the management of a distribution network, the management problems in three-phase load distribution are often ignored. In the detection of the distribution network, the three-phase load of the distribution transformer has not been regularly detected and adjusted.
(2) Unreasonable distribution of three-phase loads. Many staff who install meters and connect electricity do not have professional knowledge of and concept of three-phase load balancing. Therefore, when connecting the electricity, I did not pay attention to controlling the three-phase load balance, but just blindly and randomly connected the circuit and installed the meter, which caused the unbalance of the three-phase load to a large extent.
(3) The continuous change of electricity load. The reasons for the instability of electricity load include frequent demolition, relocation of meters, or the increase of electricity users. Instability of temporary and seasonal electricity usage.
Solution of three-phase unbalance: By adjusting the balance of the three-phase load, it can be adjusted in time according to the electricity consumption. It can also be used to adjust the three-phase balance by adding a three-phase load unbalance automatic adjustment device.
