高压直流输电线路保护动作特性分析及改进

发布时间：2018-06-16 19:18

本文选题：高压直流输电线路 + 线路保护　；参考：《华南理工大学》2016年硕士论文

【摘要】：高压直流输电线路是直流输电系统的重要组成部分,在直流线路发生故障或受到扰动时,线路保护能准确区分故障和扰动并可靠动作对于直流输电系统安全稳定运行至关重要。目前直流线路保护仍存在保护判据间的时序配合不当、保护间的时序配合不当及保护逻辑设计不当的问题。针对上述情况,本文以直流输电线路保护为研究对象,对于行波保护因保护判据间时序配合不当导致保护误动、行波保护和微分欠压保护因保护间时序配合不当导致保护动作失去选择性和纵差保护因保护逻辑设计不当导致在高阻接地故障下保护拒动等问题开展研究。针对行波保护在发生雷击故障时保护判据间时序配合不当导致行波保护发生保护误动的问题,本文通过研究对比了直流线路接地故障和直流线路雷击故障时行波保护判据间的时序配合特性,发现接地故障下行波保护在进行故障判别时其判据逻辑只会出现一次高电平信号,雷击故障下行波保护在进行故障判别时其判据逻辑会在一段时间内多次出现高电平信号的保护判据配合特征,进而提出优化行波保护判据间配合关系的改进建议,即当任意一个判据在满足保护定值并且输出高电平展宽后,在之后的一段时间内该保护判据逻辑都不能再输出高电平,防止因保护判据反复满足保护定值而出现行波保护误动的情况。针对在直流线路接地故障下行波保护和微分欠压保护动作失去选择性问题,本文结合行波保护和微分欠压保护的原理和动作逻辑,同时通过仿真分析明确了产生该问题的原因是微分欠压保护的闭锁信号——“直流线路故障重启信号RESSFP”响应时间滞后微分欠压保护动作时间,因此该闭锁信号无法在行波保护动作后可靠闭锁微分欠压保护,最后提出在微分欠压保护闭锁逻辑中增加行波保护动作闭锁信号的改进建议。仿真表明,改进方案保证了保护的选择性也兼顾了可靠性。针对在直流线路高阻接地故障下纵差保护拒动而极保护动作将故障极闭锁的问题,本文结合纵差保护原理和保护动作逻辑,同时通过仿真分析明确了产生该问题的原因是由于保护逻辑中的“延时闭锁逻辑”将纵差保护闭锁600 ms,使纵差保护出口总延时在1.1 s以上,最后提出了在纵差保护逻辑中加入交流电压UAC闭锁判据的改进建议。仿真表明,改进后纵差保护兼顾了保护的可靠性和速动性。本文研究成果为现场运行人员对于直流线路故障分析的思路、方法提供了参考,同时为直流线路继电保护运行和设计提供了理论依据,对直流输电系统安全稳定有着重大意义。本文工作得到国家自然科学基金(51377059)的资助,部分研究成果已经在实际直流工程详细模型EMTDC仿真平台上验证了其正确性和有效性。
[Abstract]:HVDC transmission line is an important part of HVDC transmission system. It is very important for the safe and stable operation of HVDC system that line protection can accurately distinguish fault from disturbance and operate reliably when the HVDC line fails or is disturbed. At present, there are still some problems in DC line protection, such as improper timing coordination among protection criteria, improper timing coordination among protection criteria and improper design of protection logic. In view of the above situation, this paper takes the DC transmission line protection as the research object. For the traveling wave protection, the protection malfunction is caused by the improper timing coordination between the protection criteria. Traveling wave protection and differential undervoltage protection due to the improper timing of protection between protection due to the loss of selectivity of protection action and longitudinal differential protection due to improper protection logic design led to the protection of high resistance to ground fault protection problems such as failure to carry out research. In view of the maloperation of traveling wave protection caused by improper timing coordination between the protection criteria when lightning strike failure occurs, In this paper, the timing matching characteristics of traveling wave protection criterion for DC line grounding fault and DC line lightning strike fault are studied and compared. It is found that only one high level signal appears in the criterion logic of downlink wave protection for grounding fault. The criterion logic of the downlink protection of lightning strike fault will appear many times in a period of time when the fault of downlink protection is judged, and the coordination characteristics of the protection criterion of the high level signal will appear many times, and the improvement of the coordination relationship between the criteria of the traveling wave protection is put forward. That is, when any criterion meets the protection limit and outputs high level broadening, the protection criterion logic can no longer output high level for a period of time thereafter. To prevent the traveling wave protection maloperation because the protection criterion meets the protection value repeatedly. Aiming at the problem of loss of selectivity of downlink wave protection and differential undervoltage protection in grounding fault of DC line, the principle and operation logic of traveling wave protection and differential undervoltage protection are combined in this paper. At the same time, through the simulation analysis, it is clear that the reason for this problem is the delay of differential under-voltage protection action time of the "DC line fault restart signal RESSFP" response time, which is the lock-in signal of differential under-voltage protection. Therefore, the locking signal can not be reliably latched after the traveling wave protection operation. Finally, the improvement suggestion of adding the traveling-wave protection action latchup signal to the differential undervoltage protection latch-up logic is put forward. Simulation results show that the improved scheme ensures both the selectivity and reliability of the protection. In view of the problem that the pole protection of longitudinal differential protection will lock the fault pole in the case of high resistance grounding fault of DC line, this paper combines the principle of longitudinal differential protection and the logic of protection operation. At the same time, through the simulation analysis, the reason for this problem is that the delay latchup logic in the protection logic will lock the longitudinal differential protection to 600msso that the total delay of the longitudinal differential protection outlet is more than 1.1 s. Finally, an improved criterion of AC voltage UAC latchup is proposed in the longitudinal differential protection logic. The simulation results show that the improved differential protection takes into account both the reliability and the rapidity of the protection. The research results in this paper provide a reference for the field operators to analyze the fault of DC line, and provide a theoretical basis for the operation and design of DC relay protection, which is of great significance to the safety and stability of HVDC transmission system. This paper is supported by the National Natural Science Foundation of China 51377059. Some of the research results have been verified on the EMTDC simulation platform of practical DC engineering.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM75;TM77

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