Dec 9 (Reuters) - SSE Plc
* SSE says it provisionally secured agreements to provide 3,239 MW of its de-rated capacity in 2020/21 in the UK electricity capacity auction on Thursday
* Says 3,794 MW of its de-rated capacity did not secure agreement, including its Peterhead and Fiddler's Ferry power plants.
* Says results will not affect existing operations at SSE's operational stations, all of which will be available this winter.
* SSE continues to analyse market conditions and opportunities for 2017 and beyond, including capacity auction in Jan. 2017 for delivery in 2017/18 Further company coverage: (Reporting by Nina Chestney)