Research On The On-Line High Potential Circuit Power Supply For Electronic Current Transformer

With the development of Power System towards to bigger unit, higher voltage, largger network and the current of short circuit become more largger. Because the electromagnetic current transformers have such shortcomings as magnetic saturation, ferromagnetic resonanceand flammable and explosive traits, it is difficult for them to keep up with the development of power system. Electronic current transformer (ECT) based on Rogowski coil not only comes over the shortcomings of the electromagnetic current transformers, but also has advantages such as high accuracy measurement, quick respondence rate, easily automatization, so it becomes the hotspot of research in domestic and international. But it needs the power supply for the units of signal process and optical transmitter in high potential circuit, so power supply is the key problem of the research of ECT.Firstly, on the basis of looking up the concerned technical literature and data both nation and abroad, the paper detailedly introduces all kinds of possible power supply for ECT in high potential circuit, gives the advantages of power supply on-line.Secondly, the struction of CT -obtain- power module is designed. And by analyzing the fundamental principle and the operating characteristic of the fast-saturation CT and slow-saturation CT, the struction of fast-saturation CT and slow-saturation CT are designed.Next, the swithing power supply circuit and speed up start-up circuit are designed. The former is used to transformer the output voltage of CT -obtain- power module into +5 V and -5 V and the later used for the ECT for protective relaying purpose is designed by instantaneous characteristic.Finally, in the condition of lab, the experimental results show that the CT -obtain- power module can supply the power above 450mW for the high potential circuit of ECT when the current on line change from 1A to 7000A. The device has some practical.