Research On Power Supplies For Hybrid Optical Current Transformer

With the development of Power System towards higher voltage, higher capacity and digitization, it is a necessity to put forward a strict requirement for the measurement facilities in Power System. Because the electromagnetic current transformers have such shortcomings as magnetic saturation, ferromagnetic resonance and flammable and explosive traits, it is difficult for them to keep up with the development of Power System. Therefore, it is an inevitable trend to develop new kinds of dependable current transformers for high accuracy measurement such as hybrid optical-electronic current transformer (EOCT). The problem of high potential circuit power supply is the key problem of the research of hybrid optical-electronic current transformer. There are some advanced studies on power supplies schemes for EOCT in this thesis, which based on a new type of EOCT for 220kV busbar researched by the laboratory. The thesis survey the realized power supplies schemes at the nation and aboard widely. Designed and realized two types of power supplies for EOCT, which is power supplies on special coil and power supplies on laser source.Firstly, the thesis introduced a EOCT scheme that supplied on a special coil. It utilized saturation of special coil to transform form 10A~720A current of busbar to 8V~40V voltage of inductions. After switched to direct current, it supplied the loads of sensor by DC-DC transformations, which is included two +5V voltages with respective ground and a group of ±12V voltage. In addition, in order to protect the circuit in the condition of high current in the busbar, the design plan is added by high voltage protect circuit and voltage monitor and control circuit and power discharge circuit. There are also some devices optimized for the circuit to reduce the ripple. The results showed that the circuit of power supplies can supply the power about 200mW for the high potential circuit of optical current transformer well.Secondly, a EOCT device supplied by laser source was realized base on researching the advanced performance of high power laser source and optical battery. After the optical battery transform the light power to electronic power that generate by laser source, the sensor of EOCT can be supplied well by the voltages that transformed form DC-DC devices. Furthermore, a high performance scheme of DC-DC transformations was introduced after the research of low power waste device.