Research On Influence Of Sympathetic Inrush On Relay Protection And Its Countermeasures

With the continuous progress of economy and society, together with the development of science and technology and informatization, global resources and energy have exposed more and more problems, which have a heavy impact on the electricity industry. In the face of requirement of sustaineable development, the electricity industry, which dare to face the problem and have the courage to take responsibility, respond positively. They are trying their best to push forward the development of smart grid, which also leads to the performance of relay protection devices must be strengthened. In the power system, relay protection device is the first line of defence, as well as the key position of transformer, the reliability of the transformer protection affects the stable operating of the whole system. As a result, transformer protection is of great importance.This paper mainly studied the sympathetic inrush in the transformer, firstly studied the theory of how sympathetic inrush generated, and then built three types of sympathetic inrush models in the use of MATLAB software, the generated process and some factors are simulated directly after that. In the process of simulation, this paper took the previous research results into account, studied some factors innovatively, which have great effect that can not be ignored, neglected in previous research. This paper also built a complex model which is more practical, in order to analyze the situation combined the two models before. Summarized the influence of sympathetic inrush on differential protection, residual current protection, overcurrent protection for transformer and other protection. Then use the wavelet toolbox in the MATLAB, select the appropriate wavelet to decompose and reconstruct the waveform of sympathetic inrush and current in all kinds of transformer internal fault. Then analyzed the reconstructed waveform, put forward the views of how to tell the difference of this two kinds of current. At the end of this paper, took advantage of digital substation in order to put forward some method which can be carried out easily to prevent the influence of sympathetic inrush.