Copper aluminum terminals, core components connecting copper and aluminum cables in power systems, must routinely carry stable current. However, grid operation inevitably experiences current spikes caused by motor startup and equipment switching. If these transient currents exceeding the rated value are not promptly controlled, they can easily lead to terminal overheating, contact surface oxidation, and even insulation burnout, potentially causing safety incidents. The copper aluminum terminal's overload protection mechanism is not a single-function design, but rather a multi-layered, coordinated "sense-response-protection" system. It rapidly intervenes during current spikes, limiting damage caused by excessive current while ensuring terminal connection stability, providing critical support for safe power transmission.
The copper aluminum terminal's overload protection mechanism first utilizes a precise current sensor to capture current peak signals in real time. Most copper aluminum terminals with overload protection integrate either a thermal sensor (such as a bimetallic strip) or an electromagnetic sensor. The thermal sensor is tightly bonded to the copper aluminum terminal's conductive core. When the current spike causes the terminal to heat abnormally high, the bimetallic strip deforms due to the difference in thermal expansion coefficients between the metals. The electromagnetic sensor directly detects whether the current exceeds the rated range by monitoring changes in the coil's magnetic field. These sensing elements act as "early warning devices," detecting abnormal signals at the instant of a current peak, buying time for subsequent protective action and preventing the terminal from sustaining excessive current due to delayed sensing.
Upon sensing a current peak, the copper aluminum terminal's overload protection mechanism initiates a rapid current-limiting response, interrupting or mitigating the impact of the peak current on the terminal. Some copper aluminum terminals incorporate a built-in fusible protection mechanism. Its core is a fuse made of a low-melting-point alloy, connected in series with the terminal's conductive circuit. When the current peak exceeds the rated value, the fuse rapidly heats to its melting point due to Joule heating, melting within milliseconds and directly interrupting the current circuit, preventing the peak current from continuing to flow through the terminal. Other copper aluminum terminals utilize resettable current-limiting elements. These elements actively limit current during current peaks due to the sharp increase in internal material resistivity with increasing current. After the peak passes, they return to a low-resistance state, allowing continued use without replacement. While these two current-limiting methods operate under different principles, both provide rapid intervention during current peaks, preventing the terminal from sustaining excessive current.
The copper aluminum terminal's overload protection mechanism also mitigates localized overheating damage caused by current spikes through heat dissipation. During current spikes, the conductive contact surfaces of the copper aluminum terminal are prone to generating localized high temperatures due to resistive heating. If this heat cannot dissipate quickly, it can accelerate oxidation of the contact surface and even melt the terminal's insulating housing. To address this, copper aluminum terminals with overload protection optimize their structural heat dissipation. For example, the terminal body is constructed of a high-thermal-conductivity alloy to enhance heat conduction efficiency; heat dissipation fins or hollow structures are designed around the contact surface to expand the heat dissipation area; and some terminals are filled with thermally conductive silicone to quickly transfer localized heat from the contact surface to the terminal housing. This active heat dissipation effectively reduces terminal temperature during current spikes, preventing damage to electrical conductivity and structural integrity.
To address contact loosening issues potentially caused by current spikes, the copper aluminum terminal's overload protection mechanism also utilizes a structural locking design to maintain connection stability. The transient electromagnetic forces or thermal expansion and contraction generated by current spikes can cause slight loosening of the copper aluminum terminal's crimping joints, increasing contact resistance and creating a vicious cycle of increased resistance and increased heat. To this end, the overload protection mechanism of some copper aluminum terminals incorporates a mechanical locking assembly. When it senses terminal deformation caused by a current peak, the locking clip automatically tightens the crimping bolt or plug connector, preventing the connection from loosening due to external force or deformation. Other terminals utilize an elastic contact structure, with an internal spring maintaining constant pressure on the contact surface. This ensures reliable conductive contact even with slight deformation caused by current peaks, preventing damage caused by poor contact that could exacerbate peak current.
The copper aluminum terminal's overload protection mechanism also utilizes enhanced insulation protection to mitigate the risk of insulation breakdown caused by current peaks. During current peaks, the electric field strength around the terminal can increase dramatically. If the insulation layer's breakdown resistance is insufficient, partial discharge or insulation rupture can occur, leading to leakage. Copper aluminum terminals with overload protection feature enhanced insulation material selection and structural design. For example, they use high-voltage and high-temperature resistant modified nylon or silicone rubber as insulation materials to improve the insulation layer's breakdown strength. An insulating barrier is installed between the conductive portion of the terminal and the housing to increase creepage distance. Some terminals also incorporate flame retardants within the insulation layer to prevent the spread of combustion even if current peaks cause local overheating. These insulation enhancements ensure a "leakage protection line" during current peaks, preventing safety accidents.
The copper aluminum terminal's overload protection mechanism also features interoperability with external protection systems, providing dual protection against current peaks. In complex power systems, the copper aluminum terminal's built-in protection mechanism does not operate in isolation but rather interacts with external devices such as circuit breakers and relays via signal interfaces. When the terminal's built-in protection element detects a current peak, it simultaneously sends a signal to the external protection system, triggering the circuit breaker to quickly disconnect the circuit or instructing the relay to adjust the circuit current, creating a dual barrier of "in-terminal protection + system-level protection." This interlocking design overcomes the limitations of a single protection mechanism. For example, while the terminal's built-in fuse protects only itself, interlocking with an external system can shut off the current in the entire circuit, preventing peak surges from spreading to other equipment and further enhancing the power system's overall surge resistance.
From the perspective of power transmission safety, the copper aluminum terminal's overload protection mechanism, by addressing current peaks, not only ensures the terminal's service life and stable performance, but also indirectly safeguards the safe operation of the entire power circuit. Without effective overload protection, current peaks can cause the copper aluminum terminal to burn out, leading to cascading failures such as cable shorts and equipment outages. A comprehensive protection mechanism can quickly mitigate risks when surges occur, reducing the scope of failure and repair costs. This design, centered on "active protection," makes the copper aluminum terminal more reliable in responding to grid fluctuations, meeting the stable connectivity requirements of industrial power systems and residential distribution networks, making it an essential safety guarantee for power transmission.
