Transmitting electric power into a bore hole

A bore hole extending into an earth formation, the bore hole being provided with the system for transmitting electric power into a bore hole, the system comprising an electric transmission line extending through the bore hole between an electric power source and a receiving station and voltage converter means for changing the voltage of the electric current supplied to the receiving station;

• wherein the receiving station includes frequency increasing means for increasing the frequency of electric current supplied through the electric transmission line;
• connecting means for supplying the frequency-increased electric current to the voltage converter means;
• and means for connecting an electric load to the receiving station, that the frequency increasing means is arranged to convert the electric current into three subsignals of increased frequency, each of which is 120° phase-shifted with respect to the other two, whereby the voltage converter means changes the voltage in each said subsignals, and the frequency increasing means brings the frequency of the electric current to a value in a range of between 10 and 100 kHz wherein an electric load in the form of a tool is connected to the receiving station for receiving voltage changed electric current.

A method of transmitting electric power into a bore hole, wherein electric current is transmitted from an electric power source to a receiving station via an electric transmission line, in which receiving station the voltage of the electric current supplied to it is changed in voltage converter means, wherein in the receiving station the frequency of the electric current supplied through the electric transmission line is increased by frequency increasing means, wherein the frequency increasing means convert the electric current into three subsignals of increased frequency, each of which is 120° phase-shifted with respect to the other two, whereby the voltage converter means change the voltage in each said subsignals, and that frequency increasing means bring the frequency of the electric current to a value in a range of between 10 and 100 kHz.

The method of claim 11, wherein the electric current is supplied to frequency decreasing means where the frequency of electric current supplied to it via the voltage converter means is reduced.