大型水轮发电机组继电保护若干问题研究

发布时间：2018-04-28 19:33

本文选题：大型水轮发电机 + 零序横差保护　；参考：《华中科技大学》2014年硕士论文

【摘要】：为适应可持续发展战略以及能源结构调整的需求，近年来我国大力发展水电，大量大型甚至超大型水轮发电机组投入运行，成为重要的电源支撑，其安全运行对电力系统的安全及稳定起着至关重要的作用。为保障机组的安全运行，需要配置完善的继电保护，而目前大型水轮发电机组继电保护在运行中暴露出若干问题，亟待研究解决。论文围绕这些问题，展开了深入研究和改进工作。零序横差保护是反应大型水轮发电机组匝间、相间故障的主保护，其灵敏度受不平衡电流影响较大。论文在分析不平衡电流产生原因及影响因素的基础上，，指出了目前常用的单门槛值过流判据及以机端相电流为制动量的过流判据的不足，提出以气隙感应电动势为制动量的判据，弥补了以相电流为制动量的判据的不足，二者共同作用，构成横差保护主判据，辅以反映正序突变量及三次谐波比的闭锁判据，既可准确区分内、外部故障，又大大提高了零序横差保护灵敏度。励磁系统是大型水轮发电机的重要组成部分，论文在分析励磁系统结构特性及保护配置的基础上，结合国内一起励磁系统事故案例，指出目前大型水轮发电机保护一般配置无法快速反应滑环短路故障，在故障电流分析的基础上，提出了励磁变低压侧增设一段过流段的保护方案，并通过仿真分析对该过流段的电流定值及延时给出了整定建议。大型水电厂一般有多台机组同时并联运行，如果多台机组同时失步且同时跳闸，对系统造成较大冲击而不利于恢复同步。论文利用搭建的四机-无穷大仿真模型研究了机组失步的原因，分析了现有的失步保护及失步预测保护原理，在分析多机失步的动作特性的基础上提出了基于信息交互的多机失步保护方案，即在多机信息交互及多机失步预测的前提下，失步严重机组优先跳闸，以利于其他机组的再同步，对于系统的稳定和安全运行具有重要意义。对于大型发电机组，完备、合理的保护配置及整定计算是继电保护正确行使职能的关键。本文结合国内某大型水电厂水轮发电机组保护整定工程实际，指出了整定计算及保护配置中需要注意的问题，并对这些问题进行了分析，为今后其他水轮机组的整定提供了参考意见。
[Abstract]:In order to meet the needs of sustainable development strategy and energy structure adjustment, in recent years, China has vigorously developed hydropower, and a large number of large or even super-large hydroelectric generating units have been put into operation, which has become an important power source support. Its safe operation plays an important role in the safety and stability of power system. In order to ensure the safe operation of the unit, it is necessary to configure the perfect relay protection. However, at present, some problems are exposed in the operation of the large-scale hydrogenerator set, which needs to be solved urgently. The thesis focuses on these problems and carries out further research and improvement work. The zero-sequence transverse differential protection is the main protection for inter-turn and inter-phase faults of large hydrogenerator sets, and its sensitivity is greatly affected by unbalanced current. Based on the analysis of the causes and influencing factors of unbalanced current, this paper points out the shortcomings of the single threshold overcurrent criterion and the over-current criterion which takes the terminal phase current as the braking quantity. The air-gap induction electromotive force is used as the brake quantity criterion, which makes up for the deficiency of the phase current criterion. They work together to form the main criterion of transverse differential protection and the locking criterion to reflect the positive sequence abrupt change and the third harmonic ratio. Both internal and external faults can be accurately distinguished, and the sensitivity of zero sequence transverse differential protection is greatly improved. Excitation system is an important part of large hydrogenerator. On the basis of analyzing the structure characteristic and protection configuration of excitation system, this paper combines a case of excitation system accident in China. It is pointed out that the general configuration of large hydrogenerator protection is unable to react quickly to the short-circuit fault of the slip ring. Based on the analysis of the fault current, the protection scheme of adding a section of over-current section to the low-voltage side of the excitation variable is put forward. Through the simulation analysis, the current setting and the time delay of the overcurrent section are determined and some suggestions are given. Large hydropower plants generally have multiple units running in parallel at the same time. If many units lose step at the same time and tripping at the same time, it will cause a great impact on the system and is not conducive to restoring synchronization. In this paper, the causes of unit out-of-step are studied by using the four-machine infinity simulation model, and the existing out-of-step protection and out-of-step prediction protection principle are analyzed. On the basis of analyzing the action characteristics of multi-machine out-of-step, a multi-machine out-of-step protection scheme based on information interaction is put forward, that is, under the premise of multi-machine information interaction and multi-machine out-of-step prediction, the out-of-step unit priority tripping is obtained. In order to facilitate the resynchronization of other units, it is of great significance for the stability and safe operation of the system. For large generator sets, complete and reasonable protection configuration and setting calculation are the key to the correct performance of relay protection. In this paper, the problems in setting calculation and protection configuration are pointed out, and these problems are analyzed in combination with the protection and setting engineering practice of a large hydropower plant in China. It provides reference for other turbine sets in the future.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM312;TM77

【相似文献】