LYNN – Roughly one month of work to repair electrical equipment in the city is now complete.Debbie Drew, spokeswoman for National Grid said the work was finished Tuesday after a slight delay due to thunderstorms, high heat and humidity over the past few days.?The original deadline was Monday, but it went a little beyond that,” she said. “We of course thank our customers and neighbors for their patience.”Helicopters were used as part of National Grid?s final stage of maintenance work aimed at improving electrical service on the North Shore. The helicopters installed new shield wire to protect the powerlines from lightning.The work covered three highway crossings: Route 107 in Salem; Route 129 Lynnfield Street, Lynn; and Route 1 in Lynnfield.