UK GAS-Prompt prices edge higher as lower Norwegian imports loom

* Maintenance at Norway's Kollsnes starts Aug. 17

* British gas market balanced on Friday

LONDON, Aug 14 (Reuters) - Prompt natural gas prices in Britain edged higher on Friday morning, in anticipation of lower imports from Norway next week due to planned maintenance.

Gas for delivery on Monday was trading at 40.65 pence per therm by 0850 GMT, up 0.15p from the previous settlement.

Traders said the contract rose due to a planned outage at Norway's Kollsnes processing plant, which treats gas from the country's largest gas field Troll.

Output from Kollsnes would be cut by 38.5 million cubic metres (mcm) per day from Aug 17-Aug 27 due to planned maintenance operator Gassco said.

The within-day contract slipped 0.15 pence to 40.70 pence per therm.

With supply flows at about 180.9 million cubic metres (mcm) per day and demand expected to be about 180.2 mcm, the system was almost balanced, National Grid (LSE: NG.L - news) data showed.

Friday's demand was around 22 percent above the seasonal norm of 147 mcm, the data showed, largely due to high demand for gas from power plants.

Gas plants provided 42 percent of the country's electricity on Friday morning, National Grid data showed, as gas generation made up a shortfall in other types.

Outages at two of Britain's nuclear plants were extended by operator EDF (Paris: FR0010242511 - news) on Friday, while peak wind output in the country is expected to reach 2.7 gigawatts (GW) on Friday and 2.3 GW on Saturday, compared with a maximum capacity of 8.4 GW.

In the Dutch TTF gas market, prices were also lower. Day-ahead TTF gas was down 0.05 euros at 19.60 euros per megawatt hour.

In Europe's carbon market, benchmark EU Allowances (EUA) CFI2Zc1 were down 0.02 euros at 8.18 euros per tonne. (Reporting by Susanna Twidale; Editing by David Holmes)