Testing Double-Ended Traveling-Wave Protection Schemes in Distribution Systems

As power systems decrease the amount of mechanical inertia, fast-tripping protection schemes have become critical to improve the systems’ stability. Traveling Wave (TW)-based relays for transmission level provide fast, accurate, and highly reliable protection schemes for fault detection and location. This paper provides insights and a qualitative analysis when extrapolating their application to distribution systems, where the lengths of the lines are significantly shorter. Thus the reduction in the arrival times of the reflected TWs that follow a fault can interfere with the fault location algorithms. This reduces the dependability of the protective scheme, whereas the security is maintained. Fault simulation data were loaded into a couple of commercially available TW relays using a double-ended protection scheme. The results from the playback recording feature of the relays showed that both: the subsequent reflections that follow a fault, and source sequence impedances, can interfere with the traveling wave detection algorithm, thus compromising the dependability by limiting the accuracy of the fault distance estimation.