Innovative Method for Lightning Protection of DC Power Lines Tested in a Unique Environment

Martin Pettersson, a PhD student in electrical power engineering at Luleå University of Technology, has developed and tested a new method to protect direct current (DC) power lines from lightning strikes. The tests were conducted using a spectacular full-scale model in a climbing hall in Stockholm.

The method aims to ensure that the electrical system can withstand the stresses caused by lightning strikes, a problem that risks causing significant operational disruptions.

In an attempt to simulate the damage a lightning strike could cause to DC power lines, the team created a unique experimental setup that included a mechanical construction capable of triggering a controlled “lightning strike.” The innovative solution was first tested in a climbing hall in Stockholm to mimic real-world conditions.

“We wanted to simulate a fault on the transmission line and investigate whether the protection system worked as intended. It's a project where we really had to think outside the box”, says Martin Pettersson, an industrial PhD student at Svenska kraftnät and a specialist in direct current connections.

Full-Scale Test in a Climbing Hall

Overhead DC power lines are particularly vulnerable to lightning strikes. The protection systems installed work well for alternating current (AC) power lines but require more advanced technology for DC lines. Pettersson's team therefore built a full-scale model in a climbing hall to conduct a series of mechanical tests before the system was tested on an energized power line.

“We needed sufficient drop height to test our setup, and after some deliberation, we chose a climbing hall. The receipt from the rental is probably the most unusual expense report I’ve ever submitted,” says Martin Pettersson.

By attaching a metal weight to a nylon cord, rigged on a suspended climbing rope, they were able to simulate the electrical discharge that occurs during a lightning strike.

The full-scale model was used to mimic real conditions. Photo: Svenska kraftnät

Successful live test

After the successful tests in the climbing hall, live tests were conducted on a real DC power line at a substation. There, it was confirmed that the protection systems worked as expected when the metal weight triggered a lightning strike upon contact with a grounded metal plate.

“This is the most fun I’ve had during all my years at Svenska kraftnät. It's not every day you get to simulate a lightning strike in a safe, electrical environment. If I had heard about a project like this during my studies, I probably would have thought, ‘wow, what a dream job!’"

The collaboration between Luleå University of Technology and Svenska kraftnät has resulted in a method that is not only innovative but also demonstrates the importance of thinking outside the box when it comes to critical infrastructure. The tests show that DC power lines are now better protected against lightning strikes, ensuring a safer operation of the Swedish power system.

• Electrical Power Engineering
• See video from the experiment External link.