Causing The Problem Of High Temperature In The Neutral Blocks
High temperature of neutral blocks is a common safety hazard in electrical systems, with complex and diverse causes that require high attention.
Overload current is the primary cause. When the total load of the line exceeds the designed carrying capacity of the neutral line, a sharp increase in current leads to resistance heating and a significant increase in neutral line temperature. For example, in residential buildings where multiple high-power electrical appliances are used simultaneously, if the neutral wire specifications are not upgraded synchronously, it is highly susceptible to overheating due to overload.
Poor contact exacerbates local temperature rise. If the neutral terminal is not tightened or the contact surface is oxidized, it will increase the contact resistance. When current passes through, the resistor converts electrical energy into thermal energy, causing the terminal temperature to soar. A certain factory once experienced a burnout accident of the neutral wire busbar of the distribution box, which was directly caused by loose terminal screws leading to virtual connection.
The superposition effect of harmonic currents cannot be ignored. The harmonic currents generated by nonlinear load devices (such as frequency converters) will form vector superposition on the zero line. Especially the third harmonic cannot be cancelled out, causing the zero line current to exceed the phase line, leading to overheating. Actual test data shows that after installing harmonic filters in a commercial building, the zero line current decreased by 40%.
Other underlying factors: line aging reduces the cross-sectional area of conductors, three-phase load imbalance causes the neutral line to bear additional current, and high-temperature environments accelerate insulation layer aging, all of which may induce high-temperature faults.
Prevention and control require a multi pronged approach: the line load should be regularly monitored, and wire specifications that match the electricity demand should be selected; Strengthen terminal inspection and use copper aluminum transition clamps to improve connection reliability; Install harmonic control devices and optimize three-phase load distribution; Improve the heat dissipation conditions of the distribution box and avoid high temperature and humid environments.
Timely investigation of high temperature hazards in the neutral line is not only the key to ensuring stable operation of equipment, but also an important defense line to prevent electrical fires.
