We had a broken power line at work that ran underground from a housing area out into some forested area. It was one of those old coaxial lines.

We couldn't find the break so we hired this expert.

He had something called a thumper. I was told it was a high voltage DC pulse.

It made a noise like a gunshot when it arced across the break. We started walking the line to find where the noise was loudest when it stopped.

The arc had welded the break together and the line held power again, though I never really trusted it.