Research Of Transformerdifferential Protection Based On Eletronic Current Transformer

As the increased voltage and the development of the digital substation, thedisadvantage of the traditional electromagnetic current transformer (CT) becomes more andmore prominent. The electronic current transformer (ECT) has a linear character and adigital output, and now more and more research institutes and manufactures are focus onresearching and producing it. It already has the product on running. Because ECT is muchdifferent from the CT, so the hardware and soft will be changed.Ours work is based on the equipments produced by Wuhan Huagong ElectricalAutomation Co., Ltd. As a contrast, we first give the measuring principle and the erroranalysis of CT, and those of ECT's. Also give the function and constrcture of the other partsof the ECT.The major focus is to analysis the transformer differential protection based onECT. The work includes: changing on hardware and research on interpolation algorithm, thecomparison of unbalance current based on CT and ECT, the difference and same point inmaking the ratio braking curve. After this, give the improvement of the protection softwarebased on ECT. At last, improve the second harmonic principle, adding phase judgment tothe traditional amplitude judgment. After simulation, a inproved second harmonic principlebased on three-phase transformer is given.