Sept 20 (Reuters) - Britain's National Grid on Monday said a planned outage of 1000 MW of capacity at IFA interconnector in Sellindge in Kent has been extended until Oct. 23.

"The remaining 1000 MW is unavailable until March 27, 2022 and our investigation into the fire at our site in Sellindge is ongoing," the grid said in an update on its website https://www.nationalgrid.com/incidents.

Last week, the operator extinguished a fire at its IFA interconnector site in Sellindge, part of the connector that links the French and British power grids.

National Grid has four operational interconnectors – two to France (IFA and IFA2), one to the Netherlands (BritNed) and one to Belgium (Nemo Link). (Reporting by Bharat Govind Gautam in Bengaluru Editing by Chris Reese)