Live Downed Conductor Detection RD&D

One of the most difficult and challenging wildfire ignition risks (to confidently detect, locate and to protect against) is a broken conductor that falls to the ground and then becomes an energized live electric shock and fire hazard. Live downed conductors have been a public-safety issue on utility distribution systems since the early days of overhead power system deployments, and they can remain energized on the ground for long periods of time because the current is often much lower than needed to operate a relay or a fuse. The fault currents are often below 50 amps and sometimes as low as a few hundred milliamps.

Yet another challenge is backfeed from distributed energy resources into downed conductors because customer side generation can energize downed conductors during storms even if the main feeder protective device is open.

Even though the power industry has been conducting research on detecting and preventing live, downed conductors for decades, today’s gap in the distribution systems space, is the lack of automatic detection and de-energization of the affected circuit segment. Avoidance and detection are possible, but getting to a point where true detections without having any nuisance false tripping is challenging. The key challenge being that voltage and current signatures of arcing downed conductors can be intermittent, sporadic, and generally difficult to detect with high confidence.

Information from smart meters or from SCADA can help identify some downed-conductor scenarios and modern operations centers are becoming equipped to process data to detect these scenarios with what is referred to commonly as multi-sensor fusion.

Unique Research Pathways

There are a few unique opportunities for (detecting live downed conductors) that warrant further research including:

• An active signal injection technology or (power line carrier) which may prove to be the essential supplement to optimize true positive detections and to minimize false positive detections.
• Evaluation of detection algorithms – to support intelligent sensors that are directly integrated with distribution automation (DA) devices
• Proof of concepts with innovative new sensors and detection approaches

Active Signal Injection – Power line carrier (PLC) communications is a method of using the electric system power conductors to carry an RF signal. The active signal approach proposes to use that RF signal on the distribution line and to have the protective devices listen to the line and monitor for a loss of the signal. If the signal were to go away on one or more phases, one could assume the power line is broken and may be on the ground.

A legacy PLC technology dating to the beginning of the utility industry, it is still widely used in electric utility networks for its original use case—transmission-line protective relay communication. The other widespread use of PLC technology by electric utilities is for automated meter reading (AMR), primarily in rural or remote areas, but these systems are challenging to implement on the many variations associated with multi-grounded distribution lines.

A more recent development with PLC technology is a standardization effort called the PRIME Alliance (with PRIME being an acronym for PoweRline Intelligent Metering Evolution [5]). The alliance has created open standards and protocols for narrowband PLC communications for interoperability in metering and smart-grid applications. In addition, the group has extended its work and developed a hybrid solution that integrates PLC with RF wireless. Hybrid chipsets that combine PRIME PLC with wireless are available from semiconductor vendors, and products such as meters, data concentrators, and gateways that use these chipsets are available from multiple original equipment manufacturer (OEM) vendors.

While there remains some R&D to be completed, a 2030 vision for PLC is leveraging the decades of experience with power line carrier protective relaying and applying this to high-speed protection of distribution lines in high-risk wildfire areas. Because the carrier signal rides on the power conductors, it has an inherent ability to detect broken or downed conductors. This can potentially be combined with protective devices for rapid response to open and interrupt the fault current. The PRIME Alliance hybrid solution would enable not only an ability to reach devices attached to the power line, such as grid monitoring sensors and reclosers, but the wireless component could reach environmental sensor solutions such as smoke-detecting cameras, gas-sensing detectors, and micro weather stations to provide even greater wildfire protection functionality.

Evaluation with DA Hardware – A separate use case described at this link is titled (intelligent sensor nodes) and detecting and de-energizing live downed wires is just one the many use cases for an intelligent sensor node. While DA hardware is not necessarily the key criteria for an intelligent AI enabled sensor node or monitoring system, the DA happens to be a convenient location to place the node, and to the do sectionalizing, protection, and power shutoffs as deemed necessary.

There is a need for some proof-of-concept development work at EPRI and at some of the U.S. National Labs over the near term, and assuming the results are successful, this work could be expandable to utility field demonstrations over time either within the downed conductor detection area of research or in the Smart DA (intelligent sensor nodes) areas of research.

Commercially Ready Tech – For some immediately demonstratable tech, some novel concepts have been vetted with the wildfire advisory group and each show promise for specific field demonstrations. These include:

• IND’s Early Fire Detection (EFD) System – Which demonstrates the well understood power quality monitoring principle that if at least one sensor upstream of a line break and at least one sensor downstream of the line break are used together, they provide nearly 100 percent effective detection capability for downed wires use cases.
• GridWare’s Gridscope – Multi-Dimensional Sensor Network, that demonstrates similar detection capabilities to the EFD system but adds several additional physical parameters to their data fusion and analyses.

What is needed to accelerate the industry toward the 2030 Vision?

Today’s gap in the distribution systems space, is the lack of automatic detection, locating, and de-energization of the affected circuit segment where the live conductor is on the ground. As more experience with these technologies and with new intelligent sensor nodes is attained across the power industry, it is useful to keep the live downed conductors use case in mind and to thoughtfully consider how integration with DA devices can make overall detection and de-energization of the downed conductors a reality. The next steps toward bridging this gap are to develop more specific proposals and timelines to move the work forward to utility field demonstrations.

Which 2030 Future States are Impacted by this Work?

• Smart and risk aware interface and decision support for protective and sectionalizing devices such as AI-driven adaptive protection (i.e. one-shot reclose vs PSPS)
• Signal injection and monitoring hardware capable of interface with protective devices for live downed conductor detection