An equipment failure at a Pacific Power substation in Roseburg was the culprit behind a midmorning power outage that left thousands of east and south Roseburg utility customers in the dark Friday. All 5,703 Pacific Power customers served by the substation off Diamond Lake Boulevard lost power. Customers served by Roseburg’s three other substations were unaffected, said Monte Mendenhall, regional community manager for Pacific Power. Mendenhall said that at 10:35 a.m. an equipment fault at the substation caused a protective fuse to melt. At that point, all three of the substation’s circuits went down. At 11:39 a.m., the first of …