Patent claim: An arrangement 9a 9b 9c 9d for subsea cooling of electric equipment the arrangement comprising a tank 1 the tank being filled with a first dielectric fluid 2 a housing 8 having a surface area and a volume the housing being provided in the tank comprising a capacitor unit 4 and being filled with a second dielectric fluid 3 and wherein the first dielectric fluid is pressurized to a pressure closer to ambient sea water pressure than to atmospheric pressure and wherein the housing has a surface area to volume ratio greater than 0.02 1m.

Related passage: The modular electric system 1 is placed in sea water environment at significant depth resulting in the exposure to high pressure.The modular device can be fixed to support structures located at the sea bed or it can be fixed to a submerged platform and it is supplied with electrical energy from the electrical source in a known way.The modular device 1 comprises a metal watertight container 2 filled with noncomprenssible dielectric liquid 3 of a pressure similar to the pressure surrounding the container 2 from external side of the container in which there is at least one electric system 4.In the case where are more electric systems one of it can be a control system 5.The container 2 is furnished with electric bushings 6 which are tightly fixed in the container walls for incoming andor outgoing leads of electric systems 4 and of the control system 5.In one of the walls of the container 2 there is located a compensating element 7 which compensates for increase in the pressure of the liquid 3 filling the container 2 resulting from thermal expansion of the liquid and Of the components of the system.The dielectric liquid 3 in the container 2 is oil having insulating properties and of a pressure close to the pressure of water outside the container 2.For example on the depth about 1000m the pressure of the oil in the container is about 100 bar i.e.near the same as in the sea water outside the container.The electric system 4 andor the control system 5 contains some modular functional electrical elements 8 which are placed in a protective insulating capsule 9 having a walls 10 made from resinbased compositematerial.The capsule 9 is filled with an insulating medium 11 in the form of electrically insulating gas such as nitrogen or sulphur hexafluoride SF6.The insulating medium can also be a porous substance of compressible properties for instance in the form of polyurethane foam.The insulating medium can also be a dielectric liquid in which any known pressure compensator is located which is not shown in the drawing.The pressure of the insulating medium 11 is significantly lower than the pressure in the container 2.For example the pressure of the insulating medium is about 1 atm.In the walls 10 of the capsules 9 penetrators 12 are located in which the inputsoutputs of the electrical elements 8 of the systems 4 or 5 are fitted.The electrical elements 8 generate the heat during the operation of the electrical system 4 so capsules of the electrical system 4 andor control system is furnished with means for transferring the heat from these elements outside the insulating capsule 9 of the system 4 or 5 which contain functional elements 8 needed to be cooled.These means for transferring heat could be made of electrically conductive material in the form of penetrators 12 which are extending through the wall 10 of the capsule 9 and have an electrical connection to the modular functional electrical element 8.In the preferred embodiment of the invention the electric system 4 contains one of the module 9 in the form of the inverter which is furnished with the wireless communication means.In this case the control system 5 also is furnished with such means.The details of this embodiment are presented in later part of the description.