What did we learn?
PG&E has 27% underground distribution and 1% underground transmission. When PG&E completes their $30B underground program (for fire mitigation) and undergrounds 10,000 miles of distribution, they will have 37% UG.
Exelon has major High Pressure Fluid Filled (HPFF) transmission lines in Chicago, Philadelphia, Baltimore and Washington, DC. They need to replace the antiquated HPFF with solid di-electric cables and have a segment of super conductors installed between two downtown Chicago substations.
Anaheim has a 4% electric rate surcharge that has funded their major 12kV underground program for the last 35 years. They are 60% underground and have an underground gas insulated switchgear (GIS) substation.
Each utility provided real capital cost data for underground versus overhead and all agreed that the O&M cost for underground was lower.
Did we answer the 50% UG by 2040 question? Well, maybe another paper and article in T&D World is needed.