Improving Controlled Closing to Reduce Transients in HV Transmission Lines and Circuit Breakers

It is widely known that controlled switching of transmission lines reduces the transients in power systems. In this paper, the circuit-breaker (CB) closing time sequence for transmission lines with various configurations is studied and improved. A theoretical analysis based on modal analysis of traveling waves and inverse Laplace transform is used to find the actual zero voltage crossing point of the poles of CB. The transmission-line coupling effect and its effects on controlled closing sequence are also considered. In addition, the minimum requirement for dielectric strength and operating time deviation of the CB is extracted for successful controlled closing. Finally, comprehensive simulation studies are performed to obtain the optimum closing sequence for various lines configurations. It is shown that transmission-line overvoltages are reduced using the proposed controlled closing method.