高压直流输电系统线路保护、故障重启及故障测距方法的研究

发布时间：2019-05-11 20:31

【摘要】：高压直流输电(High Voltage Direct Current,HVDC)以其在输电稳定性、可控性、经济性等方面的优势,正逐步成为我国远距离、大容量输电及大区域联网的重要方式,其运行可靠性不仅关系到系统本身及内部设备的安全,甚至会对整个电网的运行稳定性造成重大影响。相关统计数据表明,直流系统故障主要为直流线路故障,因此,灵敏、可靠的直流线路继电保护,准确、快速的直流线路故障测距和故障重启策略,对于保障高压直流输电系统安全的意义重大。在直流线路保护方面,目前普遍采用以行波保护为主保护,辅以微分欠压保护和纵联差动保护的配置方案,该配置方案可以正确动作于大多数线路故障类型,但在线路发生高阻接地故障时存在拒动的问题。在直流线路故障测距方面,目前主要采用行波测距法,但当故障接地电阻较高或故障行波较弱时,行波法存在波头不易检测、存在出口死区等问题。在线路故障重启方面,目前采用的重启方式为定延时重启,若重合于永久性故障,将对输电系统造成二次冲击,危害系统及输电设备安全。针对以上问题,本文的主要工作包括:(1)带直流线路开路试验中开路电压的计算借鉴不带线路开路电压公式的推导方法,通过分析直流设备及线路元件对开路电压的影响,确定带线路开路电压的稳定条件,并通过对现有不带线路开路公式进行修正,给出适用于带线路开路试验的开路电压计算公式。该公式可用于修正开路试验电压保护的动作门槛值,防止开路试验电压保护在进行正常带线路开路试验时出现保护误动,在本文中,相关结论还用于直流线路故障重启过程中的直流线路电压分析。(2)基于直流线路电压的直流线路故障重启改进方案研究从现有直流线路故障重启策略入手,对故障极线路重启前的直流线路电压特征进行分析,利用直流线路电压在故障点消失前后的变化特征判断故障点是否消失,并以此为依据确定是否执行线路重启操作,实现直流输电线路的自适应重启。(3)智能算法在直流线路故障测距上的应用研究分别给出了基于遗传算法和神经网络算法的线路故障测距方法,讨论了智能优化算法在故障测距中的应用方式和优缺点。所提出的基于智能算法的故障测距方法可利用故障后任意时刻的数据完成故障测距,测距结果基本不受接地电阻和故障点位置的影响,同时降低了线路参数变化对测距精度的影响。(4)高阻接地故障后备保护研究在利用现有保护配置的前提下,通过修改保护配合逻辑,给出了针对高阻接地故障的改进动作方案,有效地减少了线路发生高阻接地故障时线路保护拒动情况的出现。本文针对高压直流输电线路保护、故障重启逻辑及故障测距方法存在的实际问题展开讨论,给出了相应的改进方案,所得结论对于提高直流输电系统运行的安全性、稳定性具有重要的实际意义。
[Abstract]:HVDC (High Voltage Direct Current,HVDC) is gradually becoming an important way of long-distance, large-capacity transmission and large regional networking in China because of its advantages in transmission stability, controllability, economy and so on. Its operation reliability is not only related to the security of the system itself and internal equipment, but also has a great impact on the operation stability of the whole power grid. The relevant statistical data show that the DC system fault is mainly DC line fault, therefore, sensitive and reliable DC line relay protection, accurate and fast DC line fault distance measurement and fault restart strategy. It is of great significance to ensure the safety of HVDC transmission system. In the aspect of DC line protection, traveling wave protection is widely used as the main protection, supplemented by differential undervoltage protection and longitudinal differential protection, which can operate correctly in most line fault types. However, there is a problem of rejection in the case of high resistance grounding fault. In the aspect of DC line fault location, traveling wave ranging method is mainly used at present, but when the fault grounding resistance is high or the fault traveling wave is weak, the traveling wave method is difficult to detect, and there are some problems such as exit dead zone and so on. In the aspect of line fault restart, the current restart mode is fixed delay restart. If the restart coincides with the permanent fault, it will cause secondary impact on the transmission system and endanger the safety of the system and transmission equipment. In view of the above problems, the main work of this paper is as follows: (1) the calculation of open circuit voltage in open circuit test of DC line is based on the derivation method of open circuit voltage formula without line, and the influence of DC equipment and line components on open circuit voltage is analyzed. The stability condition of open circuit voltage with line is determined, and by modifying the existing open circuit formula without line, the calculation formula of open circuit voltage suitable for open circuit test with line is given. The formula can be used to modify the action threshold of open circuit test voltage protection and prevent the protection misoperation of open circuit test voltage protection when carrying out the open circuit test of normal band line. In this paper, The relevant conclusions are also used to analyze the DC line voltage in the process of DC line fault restart. (2) the improvement scheme of DC line fault restart based on DC line voltage starts with the existing DC line fault restart strategy. The voltage characteristics of DC line before the restart of fault pole line are analyzed, and the variation characteristics of DC line voltage before and after the disappearance of fault point are used to determine whether the fault point disappears or not, and on this basis, whether to perform line restart operation is determined. The adaptive restart of DC transmission line is realized. (3) the application of intelligent algorithm in DC line fault location is studied, and the line fault location method based on genetic algorithm and neural network algorithm is given respectively. The application mode, advantages and disadvantages of intelligent optimization algorithm in fault location are discussed. The proposed fault location method based on intelligent algorithm can use the data at any time after the fault to complete the fault location, and the location result is basically not affected by the grounding resistance and the location of the fault point. At the same time, the influence of line parameter change on location accuracy is reduced. (4) the research of high resistance grounding fault backup protection under the premise of using the existing protection configuration, by modifying the protection coordination logic, An improved action scheme for high resistance grounding fault is given, which effectively reduces the rejection of line protection when high resistance grounding fault occurs. In this paper, the practical problems existing in HVDC line protection, fault restart logic and fault location method are discussed, and the corresponding improvement schemes are given. the conclusion is drawn that the safety of HVDC system can be improved. Stability is of great practical significance.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM773;TM732

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