J-A模型在变压器继电保护中的应用研究

发布时间：2018-05-17 07:26

本文选题：磁滞模型 + 励磁涌流　；参考：《山东大学》2017年硕士论文

【摘要】：电力变压器作为电力系统中的重要电气设备,在配电和输电的各个环节都被大量使用,因此变压器能否可靠的运行,将对整个电力系统的电力安全稳定起到重要的影响。随着特高压电网和智能电网的建设,为了提高系统的暂态稳定性,对变压器保护提出了更高的要求。但是同线路保护相比,变压器保护的正确动作率还有待提高,因此有必要对变压器保护作出研究与分析。首先本文针对课题的研究背景,介绍了当前的变压器保护方法。对各保护算法进行了分析,并各自的特点和可能遇到的问题进行了介绍。文章将变压器保护方法概括为三类:基于电流波形特征的变压器保护方案,基于电压波形特征的变压器保护方案,以及同时利用电流电压的变压器保护方案。并说明了单纯基于电流或电压一种电气量的变压器保护存在局限性,因此研究变压器内部磁化过程来分析变压器保护具有十分重要意义。接着在Matlab中对变压器励磁涌流进行了建模仿真,分析了当变压器饱和严重的情况下,励磁涌流中的二次谐波含量将会降低,影响二次谐波制动的判断,可能会造成变压器保护的误判;对于合闸于小匝数故障的励磁涌流,由于故障电流中包含大量的二次谐波含量,并且衰减得很慢,将会影响故障的切除时间。通过与一次三相变压器二次谐波制动误动作的案例相结合,分析了对于Y-Δ接线的三相变压器,在计算差流的转角变换过程中,由于环流的影响,使得每相差流发生变化,正常无故障合闸情况下可能会出现二次谐波含量较低的差流,这时依靠二次谐波制动原理可能会造成误判,导致保护误动。所以本文通过研究变压器内部的磁化特征,找到变压器内部涌流与故障的本质特征,避开励磁涌流的影响。本文采用Jiles-Atherton(J-A)磁滞模型来研究磁滞特性。介绍了 J-A磁滞模型的基本原理和其磁滞数学模型以及目前的研究现状,推导出J-A模型的微分方程。根据微分方程,在Matlab中对J-A磁化曲线进行了建模仿真,通过模型分析了各参数对磁滞回线的影响。最终利用遗传算法和差分进化算法实现了模型参数的识别,为利用J-A模型研究变压器保护提供了前提条件。文章通过磁滞回线特征分析说明了变压器纵联支接导纳保护方法,利用磁滞回线解释了支接导纳等效模型的意义,并依据磁滞回线面积即磁滞损耗对保护算法进行了整定。该保护避开了励磁涌流的影响,直接根据直接导纳的电导来对保护进行判定,不受涌流等谐波的影响。因为变压器是否存在励磁涌流只影响支接导纳的电纳,支接导纳的电导部分反应了变压器内部的能量损耗,对匝间短路故障十分敏感,而发生涌流与否对电导影响较小。该保护算法能够有效的识别出变压器内部小匝数的匝间短路故障、变压器投于轻微匝间短路故障等情况,具有较高的灵敏性与可靠性。此外,由于支接导纳在导纳平面上的轨迹简单,所以保护算法整定方法简单,利于进行保护计算。
[Abstract]:As an important electrical equipment in the power system, the power transformer is used in all aspects of the power distribution and transmission, so the reliability of the transformer will play an important role in the power safety and stability of the whole power system. With the construction of the UHV power grid and the intelligent electric network, the transient stability of the system will be improved. Higher requirements for transformer protection are put forward. But compared with line protection, the correct action rate of transformer protection remains to be improved. Therefore, it is necessary to make a study and analysis of transformer protection. First of all, this paper introduces the current method of transformer protection in view of the research background of the subject. The characteristics and possible problems are introduced. The method of transformer protection is summarized into three types: transformer protection scheme based on current waveform characteristics, transformer protection scheme based on voltage waveform characteristics, and transformer protection scheme using current and voltage at the same time, and simply based on electric current or voltage one kind of electric power. There are limitations in the protection of the transformer, so it is very important to study the internal magnetization process of the transformer to analyze the transformer protection. Then, the transformer inrush current is modeled and simulated in Matlab. When the transformer saturation is serious, the two harmonic content in the inrush current will be reduced and the two harmonic is affected. The judgement of the wave brake may cause the misjudgement of the transformer protection; for the inrush current which is closed to the small turn number fault, the two harmonic content in the fault current and the slow attenuation will affect the removal time of the fault. The analysis is combined with the case of the two harmonic brake misoperation with a three-phase voltage regulator. For the three-phase transformer of Y- delta connection, in the process of calculating the angle transformation of the differential flow, due to the influence of the circulation, the difference flow is changed and the difference of the two harmonic content may appear in the normal operation without fault. At this time, the two harmonic brake pros may cause misjudgement and cause the protection misoperation. Therefore, this paper will lead to the misoperation of the protection. By studying the magnetization characteristics inside the transformer, the essential characteristics of inrush and fault in the transformer are found, and the effect of inrush current is avoided. The hysteresis model of Jiles-Atherton (J-A) is used to study the hysteresis characteristics. The basic principle of the J-A hysteresis model and its hysteresis mathematical model as well as the current research status are introduced, and the J-A model is derived. The differential equation. Based on the differential equation, the magnetization curve of J-A is modeled and simulated in Matlab. Through the model, the influence of the parameters on the hysteresis loop is analyzed. Finally, the genetic algorithm and differential evolution algorithm are used to identify the parameters of the model, which provides the precondition for the study of the voltage transformer protection by using the J-A model. The line characteristic analysis shows the method of transformer longitudinal support admittance protection, and uses hysteresis loop to explain the significance of the equivalent admittance model. The protection algorithm is adjusted according to hysteresis loop area, i.e. magnetic hysteresis loss. The protection avoids the influence of inrush current and determines the protection directly according to direct admittance conductance. It is not affected by the harmonics such as inrush. Because the existence of inrush current in the transformer only affects the electrical induction of the admittance, the conduction part of the support admittance reflects the energy loss within the transformer, and is very sensitive to the interturn short circuit fault, and the inrush is less influential to the conductance. The protection algorithm can effectively identify the internal transformer. In the case of small turn to turn short circuit fault, the transformer is given to a slight turn to turn short circuit fault and so on. It has high sensitivity and reliability. In addition, because the trajectory of the admittance is simple in the admittance plane, the method of setting the protection algorithm is simple, and it is good for the protection calculation.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM41;TM774.1

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