Alfred Poor
A simple sensor system installed on existing high voltage lines helps grid operators increase capacity by as much as 40 percent.

Aging high-voltage transmission lines are a bottleneck in the power grid today, but what if a simple tweak could increase their capacity by up to 40 percent? That’s what Great River Energy in Minnesota is now looking into. After a successful pilot project last year, the company is installing 52 smart sensor motes—a.k.a. “neurons”—on their high voltage transmission lines. These motes are made by the Oslo-based company Heimdall Power. Each neuron contains sensors that help operators manage power transmission more efficiently.

One key challenge is that transmission lines lose capacity as they get hotter. As air temperatures increase, operators decrease the amount of electricity sent through the lines to minimize losses and to avoid possible power interruptions due to overheating. High voltage lines also have a “drooping” problem; the wires expand and get longer as they get hotter. This brings the bottom of the loops between towers closer to the ground, where they might be at risk of contacting trees or buildings.

The standard practice has been to set limits based on the season. These limits are often based on conservative, worst-case scenario conditions.

This approach leaves potential transmission capacity unused. The lightweight Heimdall Neurons are the size of a soccer ball and are mounted on a transmission line. They can even be installed by an autonomous drone in less than two minutes. Sensors monitor temperature and electrical current. They also can perform other important tasks on the line such as fault detection and ice monitoring. The data the Neurons collect is then processed in the cloud and delivered to operators so that they can use the full capacity of the transmission lines based on real-time data rather than best guesses as performed from a distance—which often, for safety’s sake, need to be conservative estimates.

And such information deficits, the company says, can leave power lines running at less than peak rates and real-world transmission capacity regularly unused.

“This is the first solution that can provide precise monitoring of grid capacity at scale,” says Jørgen Festervoll, Heimdall Power’s CEO. “Historically, technologies to monitor transmission lines have been expensive and difficult to deploy—and therefore only used at limited scale on a few select lines.”

Grid operators do have other options, but they are more expensive and can take much longer to implement. Building a new high-voltage line in parallel to increase capacity can cost between $1.17 million and $8.62 million per mile, according to the U.S. Energy Information Administration, and take years to construct. Another approach is to “reconductor” existing high transmission lines by replacing existing cables with “advanced overhead conductors” that can carry as much as 10 times the electricity of standard cables. Such a project can cost half as much or less than a new transmission line, and take a fraction of the time to achieve, according to the US Department of Energy.

By contrast, the Heimdall Power Neurons, Festervoll says, can be deployed quickly and at relatively low cost. The result, he says, is a significant increase in transmission line capacity at a fraction of the cost in a much shorter time compared with either building new transmission lines or replacing the existing cables.

Great River Energy started their journey with a pilot project with four Heimdall Power Neurons, Festervoll says. Using dynamic line ratings to adjust the power transmission in selected lines, the utility managed to increase transmission capacity by 42.8 percent. Building additional transmission lines to add an equivalent increase would take years and would be far more expensive. According to a company representative, deployment of the sensor balls costs just 2 to 5 percent of the cost of building a new line.