September 2011 Southwest outage started with misplaced pencil mark

摘要

An Arizona Public Service Co. technician, distracted when he was called away to perform an unrelated task, penciled in a time for a step on the wrong linenof a checklist and skipped a crucial step when he returned to complete a switching order at the North Gila substation, starting a power outage Sept. 8, 2011,nthat cascaded across the Southwest, including all of San Diego