SACRAMENTO, Calif. — A federal judge Thursday blamed uninsulated power conductors owned by PG&E for the bulk of Northern California’s wildfires the past two years — including the deadly Camp fire in Butte County — adding to the legal woes the utility is confronting. U.S. District Judge William Alsup, who is overseeing the company’s criminal probation from the 2010 San Bruno natural gas pipeline explosion, said he has tentatively concluded that uninsulated power conductors lie at the heart of the wildfire crisis that has plunged PG&E into bankruptcy. Alsup made his tentative conclusion as part of his plan, announced a week ago, to force PG&E to embark on a massive equipment inspection and tree-pruning program in advance of the upcoming fire season.