The Effect Of Oxide Layer Formation On The Conductivity Of Copper Terminal Blocks

In power transmission and distribution systems, the reliability of the copper terminal block, as the core hub for current convergence, depends heavily on the atomic-level tightness of its physical contact surfaces. When equipment is in humid or corrosive industrial environments, bare copper exposed to air is highly susceptible to chemical reactions, forming a very thin oxide or sulfide film. This non-conductive film hinders the free movement of electrons between contact interfaces, leading to a decrease in the conductivity of the copper distribution block contact surface. This microscopic performance degradation generates excess heat upon energization, causing localized temperature rises exceeding the rated range.

Contact pressure attenuation causes a surge in impedance.

The mechanical state of the connection directly determines the stability of the electrical circuit. With the periodic fluctuations of the load current, metal components undergo frequent cycles of thermal expansion and contraction.

Multiple factors leading to abnormal fluctuations in contact resistance:

• Material creep effect: Under the combined action of high pressure and thermal load, fastening bolts undergo minute plastic deformation.

• Fastening torque deviation: Initial installation torque does not meet the standard value, reducing the effective contact area.

• Vibration stress damage: Mechanical vibration causes micro-displacement at the contact points, introducing air into the contact gaps.

These mechanical changes work together to reduce the conductivity of the copper terminal strip contact surface. Once the resistance deviates from the design baseline, it not only wastes electrical energy but may also induce aging of the insulation material.

Metal fatigue monitoring during maintenance cycles

During annual preventative testing, workers can detect early signs of contact failure using infrared thermography or DC resistance testing. If the measured resistance is significantly higher than the factory specifications, it usually means that the conductivity of the copper terminal block's contact surface has deteriorated irreversibly. Cleaning carbon deposits, replacing damaged copper terminal blocks, and applying specialized conductive paste are standard procedures. For high current density applications, monitoring minute fluctuations in contact voltage drop can identify potential contact failure risks.