Erosion Characteristics of Oil-Immersed On-Load Tap Changer Contacts Under Varying Contact Speeds and Pressures

Abstract

With the growing demand for precise voltage adjustment and reactive regulation, the frequent operation of on-load tap changers (OLTCs) in oil-immersed systems has led to increased erosion of switch contacts by arcs during the switching process. This erosion causes significant wear on the contacts, thereby reducing their lifespan. Therefore, the present study aims to investigate the behavior and mechanism of arc erosion on contact surfaces in oil-immersed OLTCs. To achieve this, a self-designed friction and wear test device for OLTC contacts was utilized to conduct experiments at various sliding speeds and contact pressures. Additionally, finite element analysis was employed to validate the experimental results regarding the influence of sliding speed on arc energy. The surface morphology of the contacts was observed using an optical microscope. The findings revealed that as the sliding speed increased, the arc energy, arc initiation rate, and contact resistance initially exhibited an upward trend, then decreased, and eventually increased again. The minimum values were observed at a sliding speed of 90 mm/s. Moreover, the arc energy, arc initiation rate, and contact resistance decreased gradually as the contact pressure increased. After reaching a contact pressure of 1.5 N, the variation in the arc energy stabilized. At lower contact pressures, arc erosion dominated the wear on the contact surface. However, at higher contact pressures, the wear transitioned from predominantly arc erosion to a combination of mechanical wear and arc erosion. In summary, experimental and analytical investigations provided insights into the effects of sliding speed and contact pressure on the behavior of arc erosion, contact resistance, and surface damage of OLTC contacts in oil-immersed systems.