Power supply system comprising: - a main unit comprising a protective main housing and a distribution circuit disposed in the protective main housing; - a first module unit comprising a first protective module housing and a first electric module disposed in the first protective module housing; - a passive cooling system for cooling of the main unit and the first module unit; - a first protective connection system; and a second protective connection system, wherein the first protective connection system is configured to provide a releasable electrical and mechanical connection between the main unit and the first module unit; wherein the passive cooling system comprises cooling fins disposed on an outer surface of the first protective module housing; wherein at least one of the first protective connection system and the second protective connection system comprises a first connector device, a second connector device, and a sealing element; wherein the first connector device comprises: - a first electrical connector configured to be connected to the distribution circuit; and - a first mechanical connector configured to be secured to the protective main housing; wherein the second connector device comprises: - a second mechanical connector configured to be secured to the to the protective module housing (31a, 31b); and characterized in that the first connector device further comprises: - a first sealing surface circumferentially surrounding the first mechanical connector and the first electrical connector; wherein the second connector device comprises: - a second electrical connector configured to be connected to the electric module (40a, 40b); and - a second sealing surface circumferentially surrounding the mechanical connector and the electrical connector; wherein, when the module unit (30a, 30b) and the main unit are connected to each other: - the first and second mechanical connectors (16, 36) are connected to each other; - the first and second electrical connectors (27, 47) are connected to each other; and - the sealing element is sealingly engaged between the first and second sealing surfaces (17, 37). - a main unit comprising a protective main housing and a distribution circuit disposed in the protective main housing; - a first module unit comprising a first protective module housing and a first electric module disposed in the first protective module housing; - a passive cooling system for cooling of the main unit and the first module unit; - a first protective connection system; and a second protective connection system, wherein the first protective connection system is configured to provide a releasable electrical and mechanical connection between the main unit and the first module unit; wherein the passive cooling system comprises cooling fins disposed on an outer surface of the first protective module housing; wherein at least one of the first protective connection system and the second protective connection system comprises a first connector device, a second connector device, and a sealing element; wherein the first connector device comprises: - a first electrical connector configured to be connected to the distribution circuit; and - a first mechanical connector configured to be secured to the protective main housing; - a first electrical connector configured to be connected to the distribution circuit; and - a first mechanical connector configured to be secured to the protective main housing; wherein the second connector device comprises: - a second mechanical connector configured to be secured to the to the protective module housing (31a, 31b); and - a second mechanical connector configured to be secured to the to the protective module housing (31a, 31b); and characterized in that the first connector device further comprises: - a first sealing surface circumferentially surrounding the first mechanical connector and the first electrical connector; - a first sealing surface circumferentially surrounding the first mechanical connector and the first electrical connector; wherein the second connector device comprises: - a second electrical connector configured to be connected to the electric module (40a, 40b); and - a second sealing surface circumferentially surrounding the mechanical connector and the electrical connector; - a second electrical connector configured to be connected to the electric module (40a, 40b); and - a second sealing surface circumferentially surrounding the mechanical connector and the electrical connector; wherein, when the module unit (30a, 30b) and the main unit are connected to each other: - the first and second mechanical connectors (16, 36) are connected to each other; - the first and second electrical connectors (27, 47) are connected to each other; and - the sealing element is sealingly engaged between the first and second sealing surfaces (17, 37). - the first and second mechanical connectors (16, 36) are connected to each other; - the first and second electrical connectors (27, 47) are connected to each other; and - the sealing element is sealingly engaged between the first and second sealing surfaces (17, 37).