* Gas demand falls 15 percent below seasonal norms * Oil, equities weigh on gas curve * Power tracks losses in carbon, energy markets LONDON, Aug 19 (Reuters) - British within-day gas prices plunged 6 percent on Friday from highs seen in the previous session as gas demand fell and imports from Norway and liquefied natural gas (LNG) terminals rose to balance the system. Curve contracts also turned negative, tracking ongoing losses in the oil and global equities markets on concerns about economies slipping back to recession. Friday gas traded 3.60 pence below within-day prices seen on Thursday at 54.40 pence per therm at 0855 GMT. Contracts had shot up as high as 58.00 pence in the previous session. "Demand is lower today, it seems like it reached a level where IUK (Interconnector) turned down. Langeled flows increased yesterday (...) not sure if they are going to do the same today," one UK gas trader at a utility said. Gas demand fell day on day and slipped around 15 percent below seasonal norms, National Grid data showed. Exports to Belgium through the Interconnector were weaker on Friday, bringing down UK demand levels. Continued...

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