Industry Challenge
For most of the electric age, utilities have struggled to detect live downed distribution lines. Live downed conductors, such as the examples below, were almost impossible to detect, and they remained energized until 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.
EPRI's Response
With the introduction of more smart equipment on distribution systems and greater sophistication in utility control centers, today there are more possibilities to detect live downed conductors. In 2016, EPRI launched an effort to evaluate several technologies and approaches, performing laboratory testing and field implementations with participating utilities. Focus areas included arc-detection technologies, supervisory control and data acquisition (SCADA) and primary sensing, and smart meters.
Many relays and recloser controls now offer options to detect signatures of arcing that are present in many downed-conductor events. EPRI’s Power Delivery Laboratory has the capability and flexibility to enable researchers to test various voltages with conductors on a variety of surfaces. SCADA and primary sensing can detect broken conductors on mainlines by checking loss of voltage with status of reclosers and switches. Smart meters offer another level of feedback on the state of the distribution system because 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 could involve a live downed conductor.
Progress, Results & Next Steps
Arc detection, SCADA devices, and smart meters have all shown promise. Utilities are beginning to adopt them in their operation centers. Although each approach has advantages, none is 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 work by focusing on 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 the technologies in the control center.
How to Use the Research
The results of the research can guide utilities interested in implementing one or more of these approaches. Utilities interested in 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, one of which was released as open-source software. Although every utility has different systems in their control room, these implementations provide good starting points for integration in other systems.
How to Get Involved
Utilities can get involved in this research by performing laboratory evaluations and field demonstrations of one of these technologies. This is especially applicable for utilities with distribution automation and those with smart meters. For additional information, please contact [email protected].
