NAHANT – The entire town of Nahant was without power for a portion of Friday night, as National Grid spokesperson Jackie Barry said there was a “fault” in one of the power supply lines to the town.Barry said Nahant is fed by cables on the Lynnway, and as of 8:30 p.m. she said crews were working to get power restored before repairing the cable.”We built in a lot of redundancy into the system,” said Barry. “When a cable fails or a line goes out of service, often times we have the ability to switch customers to be serviced by another cable or another line. That’s what they’re in the process of doing right now.”As of 9:05 p.m., Barry said power was restored to “most, if not all” of Nahant.With a population of around 4,000, the power outage in Nahant is the second major outage in the Boston area this week, albeit a short one. A transformer fire on Tuesday left more than 20,000 NStar customers without power in Boston’s Back Bay for two days.Matt Tempesta can be reached at [email protected].