Distribution and sub-transmission lines do not always follow a road, and they frequently traverse large stretches or remote, unpopulated areas where no one is around to see trouble erupt. Out there in the wilderness, impending equipment failures, downed conductors and other issues that can spark a fire are rarely visible to utility engineers until flames begin. Fortunately, those same equipment problems are visible to sensors, a must-have wildfire management tool.
What kind of sensors give utility engineers a view of failing devices? Smart grid sensors that can be hot-clamped onto a line three-at-a-time in 30 minutes and will send back three vital parameters: voltage, current and a time stamp. Those three pieces of information are enough to facilitate fault location, allowing engineers to know that something has gone wrong and where on the feeder the problem occurred – particularly subtle transient fault disturbances that are not visible to SCADA.
For instance, sensors will pick up when an energized conductor has fallen to the ground. Up to 30% of faults in which a single line of conductor breaks and winds up on the ground "draw too little electrical current to blow a fuse or trip a circuit breaker" according to researchers at the Texas Wildfire Management Project at Texas A&M University. This is because in hitting the ground, the line may be hitting a surface that conducts electricity poorly. When that happens, an energized line can remain on the ground until someone notices it and, all the while, it may be producing high-temperature arcing that could cause a fire.
Another hazard that may not trip the circuit is a loose guy wire used to hold a utility pole in place. When a guy wire is broken, it can contact an energized power line, particularly on a windy day. That is an intermittent hazard that probably will not trip a breaker, but it is still quite dangerous because it may produce arcing, which can spark fires. With the right sensors, utilities will see that something is up. Better yet, they will know where to send linemen to repair the broken guy wire.
Location, location, location
Locating faults and failing equipment is one of the most valuable fire prevention and restoration tool sensors deliver.
Consider a case of conductor slap, a potential fire-starter because when lines contact each other, they could arc and eject hot particles of metal onto the ground. Conductor slap occurs when a huge rush of fault current flows through one phase of conductor and makes the line jump. If there is too much slack in the primary conductors, there's a chance the bouncing line will hit a conductor carrying another phase of power. Now, what started out as a single-phase fault turns into a phase-to-phase fault that may be missed by linemen because they will find the fault on one phase and not the other.
Smart grid sensors can identify where to look for evidence of conductor slap. What's more, only smart grid sensors can affordably provide the line-disturbance information on distribution feeders that stems from failing devices, downed conductor and other fire risks. Yes, there are other telemetry solutions. But traditional telemetry generally only lets engineers know a fault has occurred. Smart grid sensors monitor and report conditions continuously, which means they can prevent fires by alerting engineers to equipment failure that is imminent, not just failures that have already happened.
Smart grid sensors or traditional telemetry?
Traditional telemetry is also bolted onto power pole cross arms and other utility framework, which means it is permanently placed. Telemetry also costs more because it usually employs additional equipment like reclosers or relays, feeds automation technology, and it requires its own telecommunications backhaul. Even though such solutions are highly accurate, when compared to smart grid sensors, they may cost well over $100,000 including installation and project costs.
Smart grid sensors can be deployed for as little as $10,000 for a three-phase installation. They are not delivering revenue-grade accuracy, yet the accuracy and data granularity is ideal for fault and disturbance location, for network operators who are reconfiguring circuits, and for power quality engineers and distribution planners. Smart grid sensors can also easily be moved and only take a crew about half an hour to install. This makes them particularly valuable during emergency events when rapidly changing weather conditions require rapid response and enhanced visibility of conditions.
Engineers who are serious about fire mitigation should consider putting a few smart grid sensors at multiple locations on every feeder. They'll deliver information that no other equipment is providing and reveal anomalies that could spark tragedy. Smart grid sensors detect line disturbances, which represent vegetation contact, animal contact or equipment starting to fail, three leading causes of wildfire.
So, which would you rather have on your power lines? Ignition or insight? Smart grid sensors make the difference.