Fire hazard mitigation in distribution systems through high impedance fault detection

摘要

This paper assesses methods to reduce wildfires caused by power systems due to high impedance faults (HIFs). HIFs have been challenging researchers and utilities for years since their current magnitudes are below traditional overcurrent relay pickups. Most of HIFs include igniting arc between a conductor and a ground surface that may cause fire and human safety issues. Operating behavior of uni-grounded, ungrounded, multi-grounded, and high impedance grounded distribution systems are described and an actual uni-grounded system in Northern Nevada is considered for HIF study. Two different HIF detection methods based on non-harmonic and odd harmonic content of fault currents that can be used in a substation-based protective relay are described and tested in a hardware-in-the-loop (HIL) platform using a real-time digital simulator (RTDS). HIFs in different ground surfaces such as wet sand, dry sod, dry grass, wet sod, wet grass, and reinforced concrete are modelled in RSCAD software. Practical merits of the two HIF detection methods embedded in a utility-based relay is evaluated. The limitations of the relay and solutions for mitigating the fire and human safety hazard are discussed.ABSTRACT This paper assesses methods to reduce wildfires caused by power systems due to high impedance faults (HIFs). HIFs have been challenging researchers and utilities for years since their current magnitudes are below traditional overcurrent relay pickups. Most of HIFs include igniting arc between a conductor and a ground surface that may cause fire and human safety issues. Operating behavior of uni-grounded, ungrounded, multi-grounded, and high impedance grounded distribution systems are described and an actual uni-grounded system in Northern Nevada is considered for HIF study. Two different HIF detection methods based on non-harmonic and odd harmonic content of fault currents that can be used in a substation-based protective relay are described and tested in a hardware-in-the-loop (HIL) platform using a real-time digital simulator (RTDS). HIFs in different ground surfaces such as wet sand, dry sod, dry grass, wet sod, wet grass, and reinforced concrete are modelled in RSCAD software. Practical merits of the two HIF detection methods embedded in a utility-based relay is evaluated. The limitations of the relay and solutions for mitigating the fire and human safety hazard are discussed.