So what is a transformer, exactly? Two inductively-coupled coupled loops of conductor, you answer. I agree.

One of our National Laboratories had an Ethernet backbone laid in the same circular trench that held the campus high-voltage feed from the power company. Both of them were almost-complete loops.

One of the HV phases faulted to ground, which caused rather high current to flow in that phase until the protective circuit breaker or fuse operated. This caused a corresponding current to try to flow in the Ethernet backbone which followed the same path, and imposed a corresponding voltage, putting the Ethernet conductors at a much higher potential than should be on Ethernet.

This was rather hard on the network equipment, which reacted with a fine display of spitzensparks. It is truly fortunate that nobody was working on the equipment or the backbone cable; it would have been quite dangerous.

A lot of equipment, at least one router per building, got replaced, as did the Ethernet backbone. The HV cable was patched in the area of the fault. But nobody was injured, which is a Good Thing.

Big transformer.