变压器励磁涌流识别方法和抑制的研究

发布时间：2018-02-27 22:44

本文关键词： 变压器保护励磁涌流小波变换合闸策略　出处：《南京理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着我国经济的飞速发展,各行各业对电力系统提出了更高的要求。电力变压器在电力系统中起着转换枢纽的功能,其安全性和稳定性直接关系到整个电网的稳定性。虽然随着继电保护技术的不断深入,变压器保护的正确动作率也得到了提高,但是相对于线路保护、母线保护等而言,变压器保护的正确动作率仍然处于比较低的水品,究其原因是差动保护作为变压器主保护本身就存在着先天性的缺陷——其保护范围不仅包含电路而且包含磁路。当变压器空载合闸或外部故障切除电压恢复时,会产生变压器额定电流数倍的励磁涌流。励磁涌流会流入变压器差动保护回路中,从而导致变压器保护误动作。因此,本文对如何识别励磁涌流和抑制励磁涌流这两个核心问题进行了相关方面的研究。本文在广泛阅读国内外现有的变压器励磁涌流识别方法和抑制策略的相关资料,将它们合理分类并分析了它们的优点和不足之处。在励磁涌流识别方面,本文通过搭建仿真模型,得到了变压器励磁涌流和内部故障电流的波形,在此基础上提出了利用小波变化来识别励磁涌流,为了提高小波变换在识别励磁涌流的明确性,将比值法引入其中将小波变换改进,最后通过大量的仿真结果证明了该方法在励磁涌流的识别中的正确性。此外,本文深入研究了现有的励磁涌流抑制策略提出了一种串联阻容合闸技术,这种方法在考虑合闸过程中三相绕组中磁芯的变化规律基础上,结合了串联阻容的实用性,采取简单的合闸策略能够有效地抑制励磁涌流,最后通过大量的仿真结果证明这种方法的有效性和实用性。
[Abstract]:With the rapid development of China's economy, various industries have put forward higher requirements for the power system. Power transformers function as a conversion hub in the power system. Its safety and stability are directly related to the stability of the whole power network. Although the correct operation rate of transformer protection has been improved with the development of relay protection technology, compared with line protection, bus protection and so on, The correct operation rate of transformer protection is still relatively low. The reason is that the differential protection as the main protection of the transformer itself has inherent defects-its protection range includes not only the circuit but also the magnetic circuit. An inrush current of several times the rated current of the transformer will be generated. The inrush current will flow into the differential protection circuit of the transformer, resulting in the maloperation of the transformer protection. This paper studies how to identify the inrush current and restrain the inrush current of the transformer. The advantages and disadvantages of them are reasonably classified and analyzed. In the aspect of inrush current identification, the waveform of inrush current and internal fault current of transformer is obtained by setting up a simulation model. In order to improve the clarity of wavelet transform in the identification of inrush current, the ratio method is introduced to improve the wavelet transform. Finally, a large number of simulation results show that the method is correct in the identification of inrush current. In addition, a series resistive and capacitive closing technique is proposed in this paper, which is based on a thorough study of the existing inrush current suppression strategy. On the basis of considering the change of magnetic core in three-phase winding during closing, this method combines the practicability of series resistance and capacitance, and the simple closing strategy can effectively suppress the inrush current of excitation. Finally, a large number of simulation results show the effectiveness and practicability of this method.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM41;TM77

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