** Shares of power producers Talen Energy TLN.O, Constellation Energy CEG.O, and NRG Energy NRG.N rise premarket as prices at the biggest U.S. power grid auction, held by grid operator PJM Interconnection, rise to new heights

** Prices PJM cleared at $329.17 per megawatt day, 22% higher than last year's record-high of $269.92, as electricity demands continue to outstrip supply

** PJM attracted 2,669 megawatts of additional power supplies, marking the first time in the last four auctions that new generation was added

** Shares of major power-producing companies that receive capacity payments rose on the auction results; TLN rises ~9%, CEG up 5%, and NRG gains ~5%

** Up to last day's close, TLN up 55.7% YTD, CEG up 42% YTD and NRG up 70.6% YTD

(Reporting by Pranav Mathur in Bengaluru)

((Pranav.Mathur@thomsonreuters.com;))