【作者】 闫超；

【导师】 高厚磊；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2009， 硕士

【摘要】 随着我国电力系统的发展,电压等级不断升高,电网规模逐渐扩大,超高压输电线路日益增多而且承担着传送巨大功率的任务,因此维持超高压输电线路的安全稳定运行是一个十分重要的问题。在种类众多的保护类型中,基于基尔霍夫电流定律的电流纵差保护能够根据被保护元件各端的电流关系正确地判别区内和区外故障,同时还具有灵敏度高、简单可靠、动作速度快、本身有选相功能等优点,已经成为超高压输电线路主保护的首选原理之一。本文主要分为两大部分:一是原理分析;二是仿真评估。电流纵差保护的动作判据众多,本文详细分析了基于工频正弦量的全电流差动保护判据、基于故障分量相量的差动保护判据、基于故障分量瞬时值的差动保护判据和零序差动保护判据等四种判据的基本原理。同时本文对影响电流纵差保护的两个重要因素分布电容电流和电流互感器饱和进行了探讨。在高压输电线路上,分布电容等值容抗的加大使线路两端电流发生改变,从而直接影响到差动保护判据的灵敏度和可靠性。本文从理论上分析了分布电容电流的影响并给出了全电流相量判据和零序判据的补偿方案。CT饱和问题一直是困扰电流纵差保护的主要问题之一。本文给出了CT饱和时一次、二次电流的特征并对CT饱和的检测方法和抗饱和措施进行了介绍。在仿真评估部分本文首先建立了基于Matlab的一次系统模型,在此基础上在Simulink中开发了四种保护判据的差动保护模块。利用所封装的保护模块仿真了四种判据在线路正常运行、内外部故障及振荡情况下的动作行为及各种保护判据的特点。在前文原理分析的基础上仿真了全电流判据和零序判据的电容电流补偿方案,同时对由于CT饱和引起的差动保护误动作这一情况进行了仿真。在已建保护模块的基础上,为分析和学习差动保护的性能与特性提供依据,也为开发更好的保护原理提供指导,开发了基于Guide的动态仿真系统界面。更多还原

【Abstract】 With the continuous development of power system, the level of voltage gets higher and the system expands gradually. The EHV transmission lines increase day to day and they usually carry heaver power, so it is an important issue that how to maintain the EHV transition lines work safely and steady. In many kinds of protection relaying, the current differential protection based on Kirchhoff s current law can correctly distinguish the internal and external faults using relationship of the protected element current, and also it has been one of the best options for protecting EHV transmission line with the advantages of high sensitivity, simplicity, reliability, speediness and the ability of phase-selection.Two parts are included in this paper. One is principle analysis, the other one is simulation assessment. Many different current differential criterions exist at present. This paper analyzes the criteria based on the power-frequency sine vector, the criteria based on fault component vector, the criteria based on fault component instantaneous value and the criteria based on zero-sequence current differential protection etc. In addition,This paper discusses the two important factors which influence the current differential protection such as capacitance current and CT saturation. Under long distance EHV lines, increase of distributive equivalent capacitance makes both sides currents changed, which directly gives an impact on the sensitivity reliability of differential protection. Firstly, this paper analyzes the influence of distributive capacitance current and then presents compensation methods on general vector and zero-sequence current differential protection. The problem of CT saturation is very difficult all the time. This paper exhibits the character of primary and secondary current when CT is saturation. The method how to detect CT saturation and anti-saturation are also mentioned.In simulation assessment part, a Matlab based simulation system is designed and then the four protection modules are explored on Simulink in this paper. Using these packed modules, behaviors of four protection principles have been simulated under the situation such as normal operation, inside and outside faults and power swing etc. At the same time, characteristics of four criteria are assessed. Compensation methods on general vector and zero-sequence current differential protection together with maloperation caused by CT saturation are simulated in the basis of the prior analysis.To provide the basis for analysis and study on current differential, and also provide guidance towards development on a better principle, dynamic simulation system interface are designed based on Guide.更多还原