Detecting Live, Downed Conductors
Industry Challenge
For most of electrical age, utilities have struggled to detect live downed distribution lines. Live downed conductors like the examples shows on this page were almost impossible to detect, and they remained energized until they are found, posing risk to the public. In some cases, there is no visible indication that a downed wire is energized. On most medium-voltage distribution circuits, if an energized conductor drops to the ground without contacting a neutral wire, the high-impedance fault will draw less than 50 amps of current. The current is so low that normal protection does not operate, potentially leaving the public exposed to the energized wire.
Despite decades of research, this has remained an unsolved problem.
How Close are we to Usable Detection?
We are relatively close. Technologies exist today that can detect some events. With the introduction of more smart equipment on distribution systems and more sophistication in utility control centers, there are more possibilities to detect live downed conductors. More field experience and real-life experience are needed to reduce false alarms and give utilities confidence to take actions to reduce public risks. New technologies are also coming to the market that offer new strategies to detect these events.
Progress, Results, & Next Steps
EPRI has evaluated several technologies and detection approaches. EPRI performed laboratory testing and field implementations with participating utilities. Focus areas included arc-detection technologies, SCADA and primary sensing, and the use of smart meters. Many relays and recloser controls now offer options to detect signatures of arcing that are present in many downed-conductor events. EPRI tested several of these devices with downed conductors in contact with many surfaces. SCADA and primary sensing can detect broken conductors on mainlines by checking loss of voltage with status of reclosers and switches. With fast communications, detecting and tripping for falling conductors before they hit the ground is also possible. Smart meters offer another level of feedback on the state of the distribution system since broken, downed conductors can be identified by loss of voltage to meters. Algorithms were developed to use the outage management system along with pings to meters to identify and locate events that may involve a live downed conductor.
Arc detection, SCADA devices, and smart meters have all shown promise. Utilities are beginning to adopt these into their operation centers. Each approach has advantages, but none of the approaches are perfect. They can have false alarms, and they can miss some downed-conductor events. It is apparent that operators will need to consider multiple data sources to identify the most critical events. That can include weather conditions, 911 calls, loss of load on a phase, loss of voltage, and outage patterns.
EPRI is continuing this research with more laboratory testing and helping to support utility pilots and full installations. Three utilities have implemented working systems to use smart meters to identify and locate downed conductors. As more utilities implement these technologies, additional data will help improve algorithms, and utilities will learn how to best use these technologies.
How to Use the Research
The results of the research can guide utilities who are interested in implementing one or more of these approaches. Utilities interested in using smart meters can access a reference implementation of an algorithm to detect downed conductors. EPRI is working with several utilities to implement this downed-conductor detection algorithm for their systems. Three utilities have working systems, and one of these was released as open-source software. While every utility has different systems in their control room, these implementations provide good starting points for integration in other systems.
Progress and Participation
This research is underway now with ongoing project meetings and updates. If you would like more information or to understand how to get involved, contact Tom Short at tshort@epri.com.