Investigation on the Thermal Characteristics of 33-kV DC Vacuum Circuit Breakers Using 3-D Modeling

In this article, a 3D model is used to investigate the thermal performance of the 33 kV Direct Current Vacuum Circuit Breakers (DCVCBs) when operating under normal current as well as under faulty conditions. For this purpose, the 3D COMSOL program is employed, and a model is built inside. The impact of contact materials and contact resistance on the maximum temperature rise of DCVCB is investigated. The results demonstrate a clear inverse relationship between electrical conductivity, thermal conductivity, and temperature rise of the DCVCBs. In addition, the influence of contact resistance on the temperature rise is discussed. These alloy materials, namely, Tungsten-Copper (WCu), Copper-Chromium (CuCr), and Oxygen-Free Electronic (OFE Copper), are selected to be contacts of the vacuum interrupter. It is observed from the simulation results that the hot spot is formed in the contacts of DCVCBs with a temperature rise between 51 °C and 29 °C, depending on the contact material conductivity. It is found that, at faulty condition, the temperature reached 1350 °C to 4400 °C depending on the contact material. Contact resistances directly affect the temperature rise at the contact interfaces. Increased contact resistance leads to a higher temperature rise, which could degrade the material contacts of the DCVCB. Therefore, minimizing contact resistance is essential to enhance thermal stability, reduce heating at the contacts, and improve the performance of the circuit breaker.