Safety first: Detection of downed conductors and arcing on overhead distribution lines

Arcing and/or downed distribution conductors, although not of concern from an equipment damage point of view, do pose a safety threat from a personnel and property perspective. Traditional protection devices typically do not detect the fault current levels resulting from these conductor conditions. The ability to detect High Impedance (HiZ) faults has been a topic of research and development for over 30 years. About ten years ago, products began to appear on the market that could securely perform this function. Over this time period, several hundred HiZ detection devices have been placed in service and have performed to expectations. This paper examines the conductor conditions and resulting currents that are categorized as high-impedance (HiZ) faults and then reviews the HiZ fault detection principles that have evolved over time. Finally, the paper looks at the application issues encountered (both physical and procedural), and highlights experience to date.