I was sent out for a "re-thump" on a 15 kv (7200) cable for the contractors. The feed was overhead to the termination with an overhead xfmr on the same pole. The term. went to 1 ug xfmr. We thumped from the ug xfmr. Since we always thump through xfmrs without isolating them (single phase) we went ahead and thumped with the overhead xfmr connected to the overhead wire that was dead. It thumped good at the base of the pole. They had excavated the bend on the riser and about 5 feet of cable. (direct buried) Well , it was brand new cable. (couple of years old tops). We all listened to the thump. It was coming from the pole. I said lets open the cut out to the xfmr and try it again. BINGO! No thump. What was more confusing was that the fuse across the river blew hard. No pfft. It had to bang loud. You could tell by looking at it. Anyway , got out the ear muffs and gave her a try and it held. We chalked it up to the old FM theory. ( fuckin' magic) That's my story and I'm stickin' to it!