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UK GAS-Prices higher on increased demand, undersupply

LONDON, June 8 (Reuters) - British wholesale gas prices rose opened higher on Thursday due to an increase in gas-for-power demand and an undersupplied system. * British within-day gas price 0.85 pence higher at 37.75 pence per therm. * Demand is forecast at 193 million cubic metres (mcm) and flows at 170 mcm/day, leaving the system undersupplied by 23 mcm, National Grid (LSE: NG.L - news) data shows. * Demand for power generation is up by 10 mcm from Wednesday as wind output has gone down. Peak wind generation is forecast at 5.2 gigawatts (GW) on Thursday and 4.7 GW on Friday. * UK Continental Shelf supply and flows from Norway through the Langeled pipeline are both slightly lower than the previous day. * "Strong wind production cut significantly CCGT (combined cycle gas turbine) demand over the last two days," said Thomson Reuters gas analyst Marina Tsygankova. * "With (Other OTC: WWTH - news) wind speed forecast to gradually calm down over the next few days we should see return of CCGT demand.....Lower UKCS production due to maintenance at J-Block (gas fields) from tomorrow is another bullish factor," she added. * July gas contract was up 0.30 pence at 36.38 p/therm. * Day-ahead gas price at the Dutch TTF hub up 0.09 euro at 15.07 euros per megwatt hour. * Benchmark Dec-17 EU carbon contract inched up by 0.04 euro to 4.92 euros a tonne. * Thomson Reuters (Dusseldorf: TOC.DU - news) analyst view: (Reporting by Nina Chestney)