Study Of Algorithms To Identify Inrush Current Based On Improved Mathematical Morphology

How to discriminate between internal fault and magnetizing inrush current is the difficulty of transformer protection when apply differential relay.On the base of selected structural elements, this thesis indicates the relationship between the size of selected structural elements and morphological effect, and reveals"Endpoint effect"exists in mathematical morphology and its solution for the first time. In this thesis, the mechanism of inrush current occurring in transformer is well researched. A new algorithm based on improved mathematical morphology is presented for fast discrimination between inrush current and fault current of power transformers. The method is based on the principle that the waveform of the inrush distorts seriously, while the fault current nearly keeps sinusoid. Utilizing the geometric explanation of open operation and close operation of mathematical morphology, this thesis defines and extracts the concavo-convex characteristic of wave which can use to be distinguished inrush current and fault current of power transformers, and dynamic simulation shows that the method is effective. Finally, the article discusses the impact of a number of factors, such as CT saturation, non-cycle component and Frequency fluctuations.