LYNN-The Boston Street Blockbuster was late opening Monday after workers unlocked the door to find they had no power.Down the street, commuters negotiated dicey intersections left lightless after a crane in Wakefield cut power to 18,000 National Grid customers.National Grid spokesman David Graves said around 8 a.m. a crane operator hired by National Grid and working at the Wakefield junction substation hit a 115,000-volt transmission line. That caused an arcing of electricity from the transmission line to the crane.There were no injuries, but it resulted in the loss of power for customers scattered throughout Lynn, Swampscott, Salem and Everett.”Everett had the smallest number effected, around 250,” Graves said. “Salem had the largest, then Lynn and Swampscott.”Swampscott Department of Public Works Director Gino Cresta said the outage affected part of Swampscott Town Hall on Monday morning, but service was restored within an hour.He likened the early morning electrical show to that of a seventh grade science project that illustrates how electricity travels in an arc from one point to another.”I don’t mean to trivialize it,” he added quickly. “It’s how I understand it.”The arc, Graves said, caused the automated system that powers the substation to shut down, which in turn shut down the power to customers.It took a little more than an hour to power all the stations back up, which Graves said had to be done manually.”Everyone was back on line by 9:15,” he said. “And I’m sure the coffee was ready at Dunkin’ Donuts shortly after.”