Design Of Power Supply For Electric Current Transformer On High Voltage Side

With the development of higher-voltage transmission,the voltage of power line has reached a new level. For its intrinsic drawbacks, the conventional transformer can hardly meet the needs of the higher demands. A new kind of transformer-Electric Transformer (ET) becomes the focus of research. One critical problem is the power supply for the sensor head.This thesis is targeted at the 10kV bus bar. A reliable power supply is necessary to ensure the energy needed for the sensor head, regardless the state of the bus bar. By comparison of the present methods, a UPS system, which utilizes a special current transformer and batteries as a spare set, is constructed in this thesis. Once the output of CT cannot meet the needs of sensor head, batteries are driven to work immediately. Different sets of wings from different CTs are used, determined by the value of the current in the bus bar. Therefore the problems met by a single CT at a wide range of current change do not exist. This scheme combines the merits of close-loop CT and open-loop CT, decreases the startup current for this power system, at the same time avoids the impulse like induced voltage by the close-loop CT. Through rectifier, filter, stabilization and DC-DC, the voltage induced from the bus bar is converted into three stable voltages supplying to the sensor head. The results of the experiment and the simulation prove the feasibility of this scheme. This power supply can provide stable voltages for the sensor head when the current in the bus bar ranges between 2A and 500A.