【作者】 邓祥力；

【导师】 尹项根； 张哲；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2011， 博士

【摘要】 大型变压器作为电力系统的关键互联节点和功率交换枢纽,对整个电力系统的安全稳定运行和供电可靠性具有重大影响。同时,大型变压器结构复杂、造价昂贵,一旦遭到损坏,检修难度高,时间长,经济损失巨大。迄今,经过多年的努力,我国大型变压器保护装置的整体性能已取得了长足进步,但总体上正确动作率仍相对偏低。虽然造成这一局面的原因复杂,但在保护原理以及实现技术方面存在的不足是导致变压器保护发生误动或拒动的重要原因。一方面,大型变压器正常工作时铁芯磁密高,饱和倍数降低,使得传统的基于谐波制动原理的变压器保护性能劣化；绕组绕制工艺的改进,导致变压器内部匝间故障增多,对保护动作灵敏度提出了更高要求。另一方面,变压器结构形式以及与外部电网的互联方式多样,运行工况复杂,需要变压器保护对此具有良好的适应能力,同时,保护系统运行环境的复杂化也需要高可靠性的硬件平台予以支持。因此,进一步深化变压器保护原理的研究,研制开发高性能的变压器保护装置,对保证变压器的运行安全,提高电力系统的稳定运行水平和供电可靠性具有非常重要的理论和现实意义。论文首先对变压器保护的研究和应用现状以及存在的主要问题进行了分析和综述,在此基础上,重点围绕着变压器内部故障暂态仿真、变压器保护新原理以及通用型大型变压器保护装置的实现技术等方面开展了系统的研究和开发工作。变压器内部故障仿真是进行变压器保护原理研究的重要基础。变压器内部故障形式多样,其中最主要的基本故障类型是各类匝间短路和单相接地短路。论文以EMTP仿真工具中的多绕组变压器模型为基础,建立了适用于变压器内部匝间和接地故障暂态仿真的计算模型。针对模型中各绕组电感参数难以确定的技术难题,从简化参数计算,易于工程应用的角度,提出了一种基于有限动模试验或现场录波数据,通过最小二乘拟合算法确定变压器绕组电感参数的建模方法。该方法根据多绕组变压器微分方程组,把故障绕组分为短路绕组和正常绕组两部分,使用最小二乘拟合方法确定故障绕组的自感和互感参数,并由此拟合出短路绕组漏感耦合系数曲线。根据该拟合曲线和变压器短路绕组的匝数百份比,计算出变压器仿真模型的各绕组参数,从而可实现对任意匝间或接地短路故障的建模和仿真。动模试验验证了该方法的有效性。在变压器保护新原理研究中,基于变压器等值电路模型的保护原理为变压器保护性能的改善提供了一条新的途径,而模型参数的求解是该类保护应用中需要解决的关键问题之一。论文针对现有参数辨识算法在变压器稳态运行时无法求解的问题,提出了一种新的参数辨识算法以及基于统计量的参数辨识结果收敛判别标准。仿真研究表明,在变压器正常运行、空载合闸或区外故障等各种工况下,基于新模型的参数辨识算法均能准确辨识出变压器绕组参数的真实值。传统的基于谐波制动原理的变压器差动保护受谐波影响大,动作时间长,对小匝数匝间短路灵敏度较低。针对此问题,论文提出了一种基于变压器等值回路平衡方程和等效励磁电感的变压器主保护综合判据。等值回路平衡方程判据能够对变压器内部严重故障实现可靠保护,而等效励磁电感判据可有效提高保护对匝间故障的灵敏度。仿真结果表明,所提出的保护新原理不受励磁涌流的影响,动作速度快、灵敏度高。采样值差动保护以动作速度快、受励磁涌流和CT饱和影响小等独特优势受到了广泛关注。其在实际应用中面临的突出问题是定值的整定比较困难。论文以模值和制动方式的采样值差动保护为例,对影响保护灵敏度和安全性的主要因素进行进行了分析,给出了采样值差动保护定值的合理整定范围。仿真结果验证了上述结论的正确性。为了加快差流速断保护动作速度,提高抗CT饱和的能力,提出了一种基于小矢量算法的快速差流速断保护方案。论文分析了四分之一周波数据窗的小矢量算法与全周傅氏算法的内联关系,导出了两种算法间的关联矩阵,研究了小矢量算法的幅频特性,提出了快速差流速断保护的实现方案。静模测试和动模试验验证了所提出的保护方案的可行性。在上述理论研究和仿真分析的基础上,从大型变压器保护的实际需求出发,提出了通用型大型变压器保护装置的总体技术方案,并完成了保护装置的硬件设计和软件开发。硬件平台采用DSP和ARM并行工作模式,资源丰富,扩展性好,能够很好的满足统一保护软件的研发需求；通过特殊工艺设计,提高了保护装置运行的可靠性和抗干扰性能。基于保护元件模块化和动作逻辑透明化的软件设计方法,使得保护程序的开发和测试更加方便,高效,并具有良好的功能调整和扩展能力,以满足不同运行现场的应用要求。所研制的保护装置已通过了国家相关质检部门的性能测试,并在工程实际中应用,取得了良好效果。论文最后对全文进行了总结,并对下一步的研究工作进行了展望。更多还原

【Abstract】 Large power transformer, which acts as a key connecting node and power exchange junction in power system, can influence security and reliability of power system operation and power supplying dependability significantly. At the same time, once power transformer is damaged, it takes long time and is hard to overhaul it, and cause huge economic loss because of its complex structure and high price manufacture cost. Up to now, performance of transformer protective relay is enhanced significantly after many years’efforts; however, the correct operation rate is still low comparatively. Though this situation is caused by many complicate factors, insufficient research on protective principle and technical realization of relay is a key reason for malfunction or failure to operation of relay. On one hand, the normal working flux density of corn for the large transformer is higher, saturation time of corn is lower, and thus the performance of traditional transformer protection based on harmonic restraining principle is deteriorated; on the other hand, the type of transformer structure and connecting type of power system are miscellaneous and operation situation is complicate, thus transformer relay is required to have good adaptability, at the same time, high-performance hardware platform is needed to support it because complex working environments for relay. So, if the research on protective principle for transformer and development of high-performance transformer relay are further deepened, it is of great theoretical and realistic significance to insuring safety of operating transformer and enhancing stable operation level of power system and power supply reliability.First, this paper analyzes and summarizes the research, application and key problems of transformer protection. On the basis of that, this paper focuses on the study on inner fault transient simulation model of transformer, the new protective principle of transformer, and development of general-purpose relay for large transformer.Inner fault simulation of transformer is important basis to the study on protective principle for transformer. There are miscellaneous fault types in transformer. Among them, turn-to-turn faults and phase-to-ground faults are the most main and basic faults. This paper describes a method to establish turn-to-turn fault and phase-ground fault model of transformer for transient simulation with multi-winding transformer model in EMTP simulation software. There are still many technical problems to calculate out inductances of multi-winding. In term of simplifying parameter calculation and easy engineering application, this paper propose a method to establish transformer model, which uses Lest Square Method (LSM) to calculate winding inductances with limited dynamic testing or field recording date.The fault winding can be divided into two parts:normal winding and fault winding based on the differential equations of multi-winding according to the method. The Lest Square Method (LSM) can be adopted to estimate the self-inductance and mutual inductance values of the fault winding and the coupling leakage factor curve can be obtained. According to the curve and the percentage of short turns of transformer, the parameters of transformer winding for simulation can be identified, and the turn-to-turn fault and phase-to-ground fault model of transformer can be established. The dynamic test validates the proposed method in this paper.A new protective principle for transformer based on equivalent circuit provides a new way to enhance the performance of transformer relay. However, it is a key problem to identify the equivalent parameters in application. This paper proposes a new parameter identification algorithm and a convergence criterion for identification result based on statistic method. Various simulations such as transformer energizing, external fault, internal fault, and normal operation testifies that the parameter identification algorithm based on the new transformer model can estimate the winding parameters accurately in various conditions.The traditional differential protection based on harmonic restraining method is seriously influenced by harmonics, the operation time is long, and sensitivity is low, especially during slight turn-to-turn fault in transformer. Aiming to solve this problem, this paper provides a novel protective scheme based on equivalent circuit model equation and equivalent excitation inductance. The criterion of equivalent circuit model equation can provide reliable protection for serious fault while the criterion of equivalent excitation inductance enhances the operation sensitivity. Simulation shows the performance of the protection scheme is not affected by inrush current, and the protection can operate quickly and has high sensitivity. Sampled-value differential protection algorithm (SDPA) has attracted extensive attention because it has such advantages as fast operation speed, being influenced little by inrush current and CT saturation. However, the obvious week of SDPA is difficult to set the relay in application. This paper studies the security and sensitivity of SDPA with mode restraint current, conclude the setting range of SDPA. The conclusion is validated by many simulations.Aiming to accelerate operation speed of unstrained differential protection and enhance the ability of CT anti-saturation, this paper describes a fast unrestrained differential current protection algorithm based on phaselet algorithm. This paper analyzes the relationship between phaselet algorithm using sampling data of one-fourth circle and full circle Fourier algorithm, induces the conjunction array between the two algorithms, analyze magnitude-frequency characteristics of phaselet, and the fast protection criteria is proposed. The static testing and dynamic testing validate feasibility of the proposed algorithm.DSP and ARM parallel work mode is adopted in hardware platform. The platform has abundant resource, is flexible to expand, and can meet the development requirement of general-purpose protective software; Special techniques are considered in design, thus reliability and anti-interference ability of the relay are enhanced. Based on proactive software design method of module protective element and transparent operation logic, development and testing of relay software is easier, higher effective and is good to expand the protective functions to meet different field application requirements. The developed relay has passed the authorized organization testing, Feasibility is validated field application in power system.At the end, this paper summarizes all the paper and looks forward into the further research in future.更多还原