Impact of Saturated Iron Core Superconducting Fault Current Limiters on Traveling-Wave-Based Protection

Traveling-wave-based protection schemes provide fast clearance options for transmission line faults and have been increasingly used in electric power grids in recent years. Superconducting fault current limiters (SFCLs) change the impedance properties of transmission line terminals and inevitably affect protection functions based on traveling wave principles. This article is the first work that investigates the influence of saturated iron core SFCLs on traveling-wave-based protection in electric power grid applications. An electric power transmission system with a saturated iron core SFCL is modeled in an electromagnetic transients simulation program. We use a frequency-dependent line model to represent transmission lines so that transient features can be effectively captured. Single line-to-ground faults are simulated in the system. The resulting traveling waves are acquired and thoroughly analyzed. The results show that the profiles of current traveling waves are significantly impacted by the saturated iron core SFCL and the performance of traveling-wave-based protection is potentially affected. Possible mitigation strategies and directions for future studies are discussed.

I. Introduction

Superconducting fault current limiters (SFCLs) have been increasingly studied for application in high-voltage power systems to limit the magnitudes of currents in fault events [1], [2], [3], [4]. The responses of SFCLs to fault conditions change transmission line impedance profiles near terminals, and thus affect voltage and current measurements used by protective relays in substations.