Analysis of the Influence of Evolving Faults on Detection and Location Using Travelling-Wave Methods through Hardware-in-the-Loop Testing to SEL-T401L IED

Traveling-wave-based (TW-based) protection devices for fault detection and location on transmission lines are becoming increasingly prevalent in modern power systems due to their superior accuracy and fast operating performance. This study investigates modern fault detection and location techniques based on TWs using a commercial Intelligent Electronic Device (IED). The research focuses on a specific type of contingency, namely evolving faults. During single-phase faults with a \((0^{\circ})\) fault inception angle, the amplitude of the generated TWs can be minimal or even imperceptible, hindering their detection and the accurate localization of the fault point by TW-based methods. However, if the fault evolves into a three-phase short circuit, the TW protection algorithm may successfully detect and locate the fault. Therefore, the objective of this research is to analyze this specific fault condition and evaluate how TW-based protection methods respond. To conduct the study, two SEL-T401L IEDs were connected to opposite ends of a transmission line in the Paraguayan interconnected power system of 50Hz, modeled on the RTDS simulation platform. A total of 154 tests were performed, varying both the fault location and the fault evolution time. The results show that the SEL-T401L may fail to detect or locate faults using traveling-wave-based principles when the fault evolution time exceeds 35% of the power-frequency cycle (i.e., 7 ms). However, when a three-phase short circuit occurs within the first 35% of the cycle, the relay performs fast and accurate fault detection and location, with localization errors on the order of only a few meters.