High-Speed Falling Conductor Protection in Distribution Systems using Synchrophasor Data

An energized overhead power line might break and fall to the ground or other surrounding objects from reasons such as severe weather conditions, conductor aging, natural disasters, hardware failures, and/or pole knock-over. When the falling conductor touches the earth or other grounded objects, it might cause a high-impedance (Hi-Z) fault that cannot be detected reliably by conventional overcurrent protection schemes. While current-based algorithms using negative-sequence components (e.g., the ratio of |I2/I1|) can detect most broken-conductor faults in transmission systems, their efficiency is compromised in distribution systems. The performance of falling-conductor protection (FCP) schemes in distribution systems depends on several factors such as feeder topology, penetration level of distributed energy resources (DERs), broken-phase location, single-phase switching, and/or protection philosophy (e.g., type of protective devices).This paper proposes a reliable, synchrophasor-based algorithm to detect and de-energize broken overhead lines in distribution systems using PMU data inside the substation and along the feeders. The effectiveness of the proposed FCP algorithm has been validated with Hardware-in-the-Loop (HIL) testing of realistic distribution feeders using a Real-Time Digital Simulator (RTDS). A comprehensive set of cases were tested including internal/external broken conductors, internal/external faults, various DER penetration, different load levels, and transient/switching incidents. The test results show that the proposed algorithm can detect and trip broken conductors reliably. Therefore, the proposed High-Speed Falling Conductor Protection (HFCP) scheme de-energizes the affected circuit prior to the conductor hitting the ground, eliminating the risk of an arcing ground fault and energized circuits on the ground.