Contact Resistance Development of High Current Non-Overlapping Butt Contacts During a Large Number of Mechanical Switching Operations

Abstract

Over the last years, the need for HVDC Circuit Breakers became obvious. The first HVDC grids are in operation and more grids are planned. To fully utilize the advantages of a grid, fast and reliable circuit breaker technology is needed. One technology that fulfills these requirements is the Hybrid HVDC Circuit Breaker. The key component of such a breaker is an Ultra Fast (mechanical) Disconnector (UFD). Such a disconnector must have a very short opening time and very low resistance in closed position. The goal of the present work is to develop a completely novel UFD platform. To minimize the opening time, non-overlapping butt contacts are used. Even though no fault current needs to be interrupted, the contact resistance will change during a large number of mechanical switching operations. An automatic test bench is developed to investigate this behavior. The first measurement investigates the influence of a high contact force on contact resistance. The second measurement determines the change of contact resistance during many operations. Both measurements are conducted with copper and chromium based materials. The performed measurements extend the knowledge of contact resistance to higher contact forces and develop an understanding of the change of contact resistance for non-overlapping butt contacts without arcing. This will enable the dimensioning of high current contacts used in a UFD.