This article mentioned a 50.000 kV power line on 2 separate circuits on asymmetric steel poles, which connected a hydroelectric facility in Brusio/Campocologno at the Swiss-Italian Border to Lomazzo, near Milano. A quite similar power line still can be located between Morbegno and Delebio, roughly half way between Brusio and Milano, serving medium voltage. The pin insulations have been replaced though. https://reference.insulators.info/publications/view/?id=12257