The optical current transformer has the widespread application prospect in the electric power system

its power source in high-voltage side is difficult in the research

which has been restricting the application of the active current transformer.In this design

an improved power supply method is proposed

which adopts the power supply mode of the combination of the line with the battery stored energy.The principle for this supply power is introduced.The idiographic design and experiment are carried out.The experimental results show that the circuit of power can supply about 540 mW for high voltage side

when the current is small or zero.It can also provide the stabile voltage and protect the circuit at the back

when the current in line is large.The difficulties are solved in the power induced from line by CT.