Experimental Study on the Ablation Performance of CuW Contacts in a C ₄ F ₇ N/CO ₂ gas Mixture (2024)

Copper tungsten alloy (CuW) is the most widely utilized contact material for high voltage circuit breakers, where the ablation resistance of contacts significantly impacts the service life of these breakers and the safety of the power grid. This study focused on CuW contacts with varying W contents (70, 75, 80, and 85 wt%) installed in a 40.5 kV circuit breaker filled with SF<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> and 9%C<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>F<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub>N/91%CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas mixture, respectively. Twenty arc ablation experiments were conducted with interrupting current of 23 kA. Post experiment analysis included the ablation rate, contact resistance, and changes of both the surface macroscopic structure and cross-sectional microstructure. Comparative analysis was conducted to examine the effect of W content on the ablation resistance of CuW contacts in different gas environments. The results indicated that in C<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>F<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub>N/CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas mixture, the contact ablation rate, surface cracks, and contact resistance after experiments increased with the W content in CuW, showing a declining trend in arc ablation resistance. Cross-sectional analysis of pore distribution and remelted W layers revealed that the W and Cu proportions in CuW70 facilitated effective heat conduction. This composition achieved balanced performance across hardness, toughness, and electrical conductivity parameters. The results indicated optimal matching between contact material composition and the thermophysical characteristics of gas arc discharge.