A New Contact Structure and Dielectric Recovery Characteristics of the Fast DC Current-Limiting Circuit Breaker

In order to solve the problem of slow dielectric recovery caused by large arc energy when interrupting a high rising rate fault current in a fast DC current-limiting circuit breaker (FDCCLCB), a new contact structure with multi-point static contacts in parallel is proposed. Based on the principle of parallel multi-point contacts, the new structure can form the arc mode during multi-point arcing when the contacts are separated, reduce the arc energy of each finger contact, effectively reduce the ablation effect of the arc on the contact, and improve dielectric recovery ability after the arcing of the contact. Using high-speed camera technology to photograph the arc shape of the new contact, the assumption of multi-point arcing is verified, and a dielectric recovery experimental platform is built to study the dielectric recovery characteristics of the new contact structure. The experimental results show that, when the arc energy is 3.6 J and the dielectric recovery time is 60 µs, the critical field strength reaches 1.5 V/µm; when the arc energy is increased to 22 J, the critical field strength is 0.6 V/µm under the same dielectric recovery time. It can be seen that reducing the arc energy of the contact can effectively improve the dielectric recovery ability of the contact. Due to the magnetic field coupling between each finger contact, the current and arc energy on each contact are different, resulting in a weak point of breakdown and finger contacts at two ends. Finally, in order to solve the problem of large contact current at two ends, a solution to adjust the spacing among contacts is proposed. A genetic algorithm is used to optimize the spacing parameters. The optimization results show that the maximum arc energy of the finger contact is only 19.07% of the total arc energy, which greatly reduces the arc energy of the contact and improves the post-arc recovery ability of the contact.