摘要
换流器是高压直流系统中的核心装置，换流器对系统的正常运行起到决定性作用因此其保护在直流保护组最为重要，深入研究换流器保护的合理配置和原理，可提高直流输电系统运行的可靠性、可用率和经济效益。
本文详细分析换流器故障的机理和故障过程，从机理上分析了高压直流系统中整流器阀短路故障、直流侧对地短路、交流侧相间短路、误开通故障、不开通故障和换相失败等常见故障的故障机理过程，指出了上述故障的特征及其对直流系统正常运行的影响。
主要是重点通过学习与掌握PSCAD/EMTDC 的使用方法，进行了一系列针对各种故障仿真，分析仿真结果，验证故障过程，增加对故障的了解。
接着从原理上研究了换流器保护系统中的各个功能，包括阀短路、换相失败保护、交流过电压保护、直流过压保护、不正常触发保护、后备直流过流保护、大角度监视和阀直流差动保护等。
最后通过对天生桥换流站发生的测量故障进行深入分析，暴露出直流保护系统所存在的问题，并针对存在的问题提出了防范措施。通过采取这些防范措施，一方面可以提高直流系统运行的可靠性，减少不必要的闭锁事件，另一方面可以提高直流系统的可用率，减少经济损失。
关键字：故障类型,PSCAD/EMTDC 故障仿真,保护原理,保护系统,动作判据
Abstract
The converter is a high voltage DC system in the core device, a converter on the normal operation of the system has played a decisive role in the protection of DC protection group is most important, in-depth study of converter protection reasonable configuration and principle of DC transmission system, can improve the running reliability, availability and economic benefits.
This paper presents a detailed analysis of converter fault mechanism and fault process, from the mechanism analysis of high voltage DC system rectifier valve fault, DC side short circuit to ground, the AC side of inter phase short circuit fault, error, do not open the open fault and commutation failure of fault mechanism, pointed out that the fault characteristics and its to influence the normal operation of DC system.
The main focus is through the study and master the use of PSCAD/EMTDC method, undertook a series of to all kinds of fault simulation, the analysis of simulation results, verify the failure process, increase understanding of fault.
Then from the principle of converter protection system in various functions, including the valve short circuit, commutation failure protection, AC over voltage protection, DC overvoltage protection, abnormal triggering protection, backup DC over current protection, large angle monitoring and valve direct current differential protection.
By the end of the Tianshengqiao converter station the measurement fault analysis, reveals the DC protection system existing problems, and put forward some preventive measures. By taking these measures, one can improve the reliability of DC power supply system, reducing unnecessary locking event, on the other hand, can improve the availability ratio of DC system, reduce economic loss.
Keyword : fault type; PSCAD/EMTDC fault simulation, protection philosophies,protection systems, dectection principles
