1 leg on our 3 phase 600 volt service would trip at the pole every time we came near half of what we were allowed to draw.

It went on for years before the power company finally changed the transformers.

Apparently they knew what was wrong but they figured it was cheaper to send crews out to install fuses.

Finally one of the linesmen installed a fuse that was much too large by "mistake" and actually caught their pole on fire. That moved it up the priority list.