PG&E Corp. said it would begin shutting off power to 179,000 customers in 17 California counties on Wednesday afternoon, its second major intentional blackout this month meant to head off potential wildfires. The shut-offs were expected to begin at 2 p.m. local time in the Sierra Nevada foothills and 3 p.m. in some counties north of San Francisco. More are planned for 1 a.m. Thursday in parts of San Mateo County, between San Francisco and San Jose, and Kern County, in the southern part of the state’s Central…