Solid state switching device comprising: - a pair of line terminals (T1, T2) including first and second line terminals for electrical connection with a corresponding phase conductor of an electric line; - a switching assembly including one or more solid state power switches, said switching assembly having first and second power terminals (P1, P2) electrically connected with said first and second line terminals, respectively; - a heat sink element in thermal coupling with said switching assembly to adsorb heat from said switching assembly; characterised in that it comprises: - an additional heat extraction arrangement to extract heat from said switching assembly and convey the adsorbed heat along said phase conductor through said first and second line terminals; wherein said additional heat extraction arrangement comprises: - a first electro-thermal conductor element thermally coupling said first line terminal with said switching assembly and electrically coupling said first line terminal with said first power terminal; - a second electro-thermal conductor element thermally coupling said second line terminal with said switching assembly and electrically coupling said second line terminal with said second power terminal; wherein each electro-thermal conductor element (7, 8) is formed by a plate of thermally and electrically conducting material, wherein each line terminal (T1, T2) is mounted on a corresponding electro-thermal conductor element (7, 8), wherein each electro-thermal conductor element (7, 8) is positioned in proximity of said heat sink element, wherein said additional heat extraction arrangement further comprises: - a first thermal interface element thermally coupling said first electro-thermal conductor element with said heat sink element and electrically insulating said first electro-thermal conductor element from said heat sink element; - a second thermal interface element thermally coupling said second electro-thermal conductor element with said heat sink element and electrically insulating said second electro-thermal conductor element from said heat sink element; wherein each thermal interface element (9, 10) is positioned between a corresponding electro-thermal conductor element (7, 8) and said heat sink element. - a pair of line terminals (T1, T2) including first and second line terminals for electrical connection with a corresponding phase conductor of an electric line; - a switching assembly including one or more solid state power switches, said switching assembly having first and second power terminals (P1, P2) electrically connected with said first and second line terminals, respectively; - a heat sink element in thermal coupling with said switching assembly to adsorb heat from said switching assembly; characterised in that it comprises: - an additional heat extraction arrangement to extract heat from said switching assembly and convey the adsorbed heat along said phase conductor through said first and second line terminals; - an additional heat extraction arrangement to extract heat from said switching assembly and convey the adsorbed heat along said phase conductor through said first and second line terminals; wherein said additional heat extraction arrangement comprises: - a first electro-thermal conductor element thermally coupling said first line terminal with said switching assembly and electrically coupling said first line terminal with said first power terminal; - a second electro-thermal conductor element thermally coupling said second line terminal with said switching assembly and electrically coupling said second line terminal with said second power terminal; - a first electro-thermal conductor element thermally coupling said first line terminal with said switching assembly and electrically coupling said first line terminal with said first power terminal; - a second electro-thermal conductor element thermally coupling said second line terminal with said switching assembly and electrically coupling said second line terminal with said second power terminal; wherein each electro-thermal conductor element (7, 8) is formed by a plate of thermally and electrically conducting material, wherein each line terminal (T1, T2) is mounted on a corresponding electro-thermal conductor element (7, 8), wherein each electro-thermal conductor element (7, 8) is positioned in proximity of said heat sink element, wherein said additional heat extraction arrangement further comprises: - a first thermal interface element thermally coupling said first electro-thermal conductor element with said heat sink element and electrically insulating said first electro-thermal conductor element from said heat sink element; - a second thermal interface element thermally coupling said second electro-thermal conductor element with said heat sink element and electrically insulating said second electro-thermal conductor element from said heat sink element; - a first thermal interface element thermally coupling said first electro-thermal conductor element with said heat sink element and electrically insulating said first electro-thermal conductor element from said heat sink element; - a second thermal interface element thermally coupling said second electro-thermal conductor element with said heat sink element and electrically insulating said second electro-thermal conductor element from said heat sink element; wherein each thermal interface element (9, 10) is positioned between a corresponding electro-thermal conductor element (7, 8) and said heat sink element.