【作者】 李正天；

【导师】 林湘宁；

【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】 随着电网规模越来越庞大,电压等级越来越高,如何可靠地保证电网安全稳定运行,是我国电网日益面临的严峻挑战。近年来美国、欧洲相继发生大停电事故,充分说明了寻求更加安全、可靠的电网保护控制措施是当前电力行业的一个重要课题。论文结合电力系统生产运行实际,围绕现有继电保护领域存在的一些难点和热点问题,开展了多方面的深入研究。研究提出了一种新的差动保护动作行为分析方法,该方法可以评估任一种比例差动判据在各种可能的运行条件下的动作性能,利用这种分析方法,详细分析了ABB公司两种标积制动判据的安全性和灵敏性。在对全电流差动判据和故障分量电流差动判据的比较方面,论证了在多种内部故障的情况下,故障分量电流差动保护的灵敏性和安全性明显优于全电流比例差动保护；在相电流差动保护和线电流差动保护的比较方面,论证了相电流差动保护在反应接地故障、尤其是单相接地故障时的综合灵敏度比线电流差动保护有所提高,因此,采取零序差动等补偿措施的做法是有意义的。详细研究了采样值差动判据的动作性能,给出了动作电流倍数与电流采样初相角存在的对应函数关系,并论证了采样值差动保护中关于模糊动作区上下界的结论。电力系统振荡期间,需要有效快速闭锁距离保护以免误动,但是对振荡过程中发生的三相对称故障,又需要快速识别并解除对距离保护的闭锁。通过研究振荡过程中系统频率及其变化规律,提出了一种面向继电保护的全过程系统振荡模型,在此基础上,提出了一种基于三相有功及三相无功变化率的距离保护振荡闭锁新方法,基于该方法,在振荡的各个阶段,距离保护都能可靠地被闭锁；而对称故障发生后,该方法能够快速动作,不受系统参数、故障时刻、故障位置等因素的影响。研究提出了一种适应工程要求的自适应振荡闭锁新策略,在各种系统振荡的情况下,本策略均具有足够的安全性,当振荡中发生区内故障时,除了高阻接地故障,其灵敏度在各种现有策略中是最高的。在广域保护方而,研究提出了一种分层电力系统区域保护系统,与现有的主保护后备保护协同工作,构成强化后的电网第一道防线,此区域保护系统的动作速度介于保护和后备保护之间,进一步提高了整个保护系统的安全性。针对距离保护Ⅲ段和过保护因潮流转移引起误动的问题,提出了自适应调节保护定值的方法,仿真计算结果明该调节方法简单有效,既可以避免由于潮流转移引起的误动作,又可以在线路发生障时不失去远后备保护的功能。最后对全文的研究成果进行了总结,并提出了今后进一步的研究方向。更多还原

【Abstract】 In view of the scale-up of power grids and rise of the voltage levels, how to guarantee the safe and stable operation of power grid is turning to be a more and more serious challenge to power grids. In recent years, the successive blackouts in America and Europe have adequately proved the significance of searching for secure and reliable protective measures for the purpose of safety and reliability of power system operation. Therefore, a series of difficulties and issues existing in the field of protective relaying are investigated. Taking the actual operation scenario into account, in-depth studies from various aspects are conducted.In this dissertation, a novel method is put forward to analyze the performance of differential protection, which is able to evaluate any kind of percentage differential criteria under any operating scenarios. What’s more, the security and sensitivity of two scalar product restraint criteria are analyzed by use of this method.In comparison with the security and sensitivity between phase current based differential criterion and fault component current based differential criterion, it can be proved that in the condition of many internal faults. The performance of fault component based differential protection is superior to the other one. At the same time, it can be disclosed that in the condition of earth faults, especially single-phase earth fault, phase current differential protection is superior to phase current based criterion in terms of integrated sensitivity. Therefore, some enhancement like zero-sequence differential compensation is worth adopting.According to the performance analysis of instantaneous-value based differential criterion, the corresponding functional relation between the multiple of operating current and initial phase angle of sampled current is disclosed. Furthermore, the study on the fuzzy operating area of instantaneous-value differential protection is demonstrated as well.During the power swing, the effective and quick blocking scheme for distance protections is required to avoid unwanted tripping. On the other hand, the rapid recognition for the three-phase symmetric fault is needed to unblock the distance protection. By studying the system frequency and the regular pattern of it during the power swing, an overall process power swing model for relay protection study is implemented. Based on this model, a novel method for power swing blocking in distance protection by means of the change rate of three-phase active power and reactive power is put forward. The simulation test results show that the distance protection can be blocked reliably in any period of the power swing by using this method. When symmetric faults occur, it can unblock the distance protection rapidly, which is immune to the influence of factors such as system parameters, fault occurring moment and fault position, etc.A novel strategy for self-adapting swing blocking meeting the engineering demands is proposed. It is proved as secure enough under any circumstance of power swings. When faults occur during the power swings, the sensitivity of this strategy is the highest among the available strategies as long as the fault resistance is not very high.In the aspect of wide-area protection study, a kind of regional protection system based on layered power system is put forward to cooperate with the existing main protection and back-up protection. The speed of this protection system is between the main protection and back-up protection, which increases the security of the whole protection system. Aiming at solving the problem of the Zone III of distance protection, as well as the overcurrent protection unwanted tripping caused by load flow transferring, a method of self-adaptive adjustment of setting is proposed. It is verified with the PSASP based simulation that this adjusting method is simple and effective, which could avoid unwanted action tripping by load flow transferring. Meanwhile, the functionality of remote back-up protection can be reserved when the faults occur on the adjacent lines. Finally, the achievements of this dissertation are concluded and the future work is prospected.更多还原