A Composite Line Protection Scheme for Flexible HVDC Transmission Systems with Outward-shifted Current Limiting Reactors

Abstract

Based on the practical needs of efficiency-improving and cost reduction in the construction, operation, and maintenance process of flexible DC transmission systems, the optimization of DC system topology has attracted more attention in the industry, among which the optimal design of converter installation location, structure, and parameters of such systems has the most trend of popularization and application. However, the such proposal will directly change the path and propagation characteristics of the fault traveling wave (TW) when the DC transmission system fails, significantly change the fault characteristics, and seriously reduce the operation performance and adaptability of any applied relay protection schemes. Based on a comprehensive RTDS model of real system parameters, this paper quantitatively analyzed the occurrence and development law of fault characteristics in the optimized topology, through which the influence of fault attributes on the steepness and subsequent development trend of TWs is widely utilized, and a principle of using difference development sum of local measurements to realize detection, identification and rough location of faults is proposed. The composite of it and a bilateral current direction criterion can effectively improve the anti-interference ability and reliability of the overall protection scheme.