Characterization of the Airflow Distribution near a Circuit Breaker’s Cu-Ag-Alloy Electrode Surface during and after Breakdown

Abstract

Circuit breakers, affected by multiple lightning strikes after the breaker has been tripped, can break down again, which will reduce the life of the circuit breaker and threaten the stable operation of the power system. Aiming at this problem, this research obtained the temperature diffusion process of the inrush current process of the circuit breaker’s opening and breaking, using the Schlieren technique combined with existing image recognition technology to obtain the temperature characteristics of the airflow in the air gap of the contact, as well as the characteristics of the flow of air itself. The results of the study show that the circuit breaker breakdown process generates a shock wave with a velocity approximately equal to the speed of sound under the same conditions. The maximum velocity of the airflow boundary diffusion is about one-quarter of the speed of sound under the same condition, and it decays very fast, reducing to the airflow drift velocity within 10 ms after breakdown. The maximum temperature of the thermals is concentrated between 6000 K and 8000 K, and the temperature change is approximately inversely proportional to the square of the time. This research provides the basis for the design of a circuit breaker’s contact structure, opening speed optimization method, interrupter chamber, and insulation design optimization.