【作者】 金明亮；

【导师】 尹项根； 游大海；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2010， 博士

【摘要】 大型发变组的安全可靠运行对保障电力系统安全稳定具有重大作用,但其运行工况较为复杂,从而给发变组主保护带来了较大影响,因此不断提高发变组主保护性能及研究新保护原理具有重要意义。本文主要围绕大型发变组复杂异常工况及相关保护问题展开研究,内容包括发变组复杂和应涌流机理及特征,复杂和应涌流导致的差动保护误动原因与对策,基于瞬时功率原理的新型发电机主保护,抽水蓄能同步电机弱功角稳定性及新型低功率保护等。针对复杂和应涌流导致差动保护误动问题,构建了复杂和应涌流研究模型,利用LAPLACE变换获得了变压器磁链和电流的解析表达式。通过推导分析和数字仿真研究指出,在系统电源、发电机电源和负荷电流的共同作用下,复杂和应涌流呈现出指数函数与双曲函数联合特征,变压器副方其它形式的电源均对复杂和应涌流有影响。揭示了复杂和应涌流中二次谐波变化特征,分析了复杂和应涌流中非周期分量对电流互感器的影响,为后文研究新保护技术提供了理论基础。结合复杂和应涌流机理特征和电流互感器暂态饱和特点分析了复杂和应涌流导致变压器差动保护误动的原因,并进行了相应的数字仿真。通过仿真研究指出了复杂和应涌流暂态过程中保护侧差流,制动电流和二次谐波含量变化特征,提出了基于差流和二次谐波二维特征的变比率制动变压器差动保护。该保护不受复杂和应涌流影响,动作灵敏可靠,有效解决了常规差动保护在复杂和应涌流暂态过程中的误动问题。通过数字仿真和现场录波数据分析指出了在复杂和应涌流暂态过程中发电机差动保护原因,结合二次谐波制动和比率制动提出了一种加强制动型发电机差动保护。该保护通过加强制动功能来防止复杂和应涌流或外部故障导致保护出现误动行为,同时采用基于差流和制动电流计算公式的制动开放判据来避免发电机内部相间故障下保护出现拒动。各项试验数据和结果均证明了加强制动型发电机差动保护具有很高的灵敏性和可靠性,已经在工程现场获得成功应用。数字化电站技术的发展将使电压量能可靠用于主保护,因此基于电流电压量的功率保护技术因其简单可靠的特点将得到大力发展应用。论文基于两相(α,β)坐标系统对发电机内外部故障时其输出的瞬时功率进行了研究,提出了瞬时功率不对称度定义,并以瞬时功率不对称度为主判据,结合不平衡功率的相位特征提出了一种新型发电机不对称故障保护。动模试验结果表明,该保护具有很高的灵敏性和可靠性,且该保护接线简单,易与其它类型保护集成互补使用。对抽水蓄能电站保护进行了整定计算,为解决抽水蓄能同步电机处于抽水工况下电机低功率保护易出现误动问题,论文研究了同步电机处于抽水工况下功率振荡特点,分析了常规低功率保护容易出现误动的原因。通过数字仿真和现场数据分析,提出了一种新型多段式低功率保护。该保护的各段低功率定值与延时定值相匹配,能适应电机功率振荡不同阶段的特点,具有较高的可靠性。论文最后对全文研究成果进行了总结,并指出了下一步研究方向。更多还原

【Abstract】 It is very important that the large generator-transformer unit is in safe and reliable running conditions for the electric power safety and reliability. The running conditions of the generator-transformer unit usually are complex, and the running conditions’conversion of the pumped-storage hydro-plant is in high frequency especially. It has a strong impact on the performance of the primary protections of the generator-transformer unit. Therefore it is of great significance to improve the performance of the main protection and research the new protection theory continuously. This paper focused on the complex and abnormal running conditions of the large generator-transformer unit and its protection problems. It contained the complex sympathetic inrush theory and characteristics, the differential protection mal-operation reasons caused by the complex sympathetic inrush and its countermeasures, the novel primary protection of generator based on the instantaneous power theory, the weak power-angle stability of the pumped-storage synchronous machine and the novel low power protection.This paper constructed the study model of the complex sympathetic inrush in order to solve the differential protection mal-operation problem caused by the complex sympathetic inrush. The analytic expressions of the flux linkage and current of the transformer were obtained by the LAPLACE-transform and were analyzed in detail. By the theory derivation and the digital simulation, it was pointed out that there were the joint characteristics of both the exponential function and the hyperbolic function under the system power, generator power and load current. Other powers in the transformer secondary windings had influence on the complex sympathetic inrush. Meanwhile the paper revealed the characteristics of the second harmonic current. All the research results provided the theory basis for the novel protection technology study.Based on the theory and characteristics of the complex sympathetic inrush, this paper analyzed the reasons of the transformer differential protection mal-operation caused by the complex sympathetic inrush. The joint digital simulation model of the generator-transformer unit was established. By the simulation study, the characteristics of the differential current, the restraint current and the second harmonic current in the protection were presented. A novel transformer differential protection with the variation ration restraint was proposed. It was unacted on the complex sympathetic inrush and the sensitivity and reliability were good. The mal-operation problem of the classic differential protection was solved by the novel protection effectively.By the digital simulation and the field record data analysis, the mal-operation reason of generator differential protection was concluded. A novel generator differential protection with the enhance restraint function was proposed based on both the second harmonic restraint and the ration restraint function. The mal-operation behavior of the differential protection during the complex sympathetic was blocked by the enhanced restraint function. Meanwhile a special opening criterion concluded from the calculation formula of the differential and restraint current was applied to avoid the refusing action of the protection in the condition of the phase to phase fault. The sensitivity and reliability of the differential protection with the enhanced restraint function were proved by all the test data and results, and the novel generator differential protection with the enhance restraint function had been put into use in the field.With the development of digital power substation technology, the voltage quantity could be used in the primary protection, and the power protection would be applied widely for its simple and reliable features. This paper studied the output instantaneous power of generator when an inner or extent fault took place in generator in the (α,β) coordinate system. The instantaneous power asymmetry degree was defined. A novel generator asymmetry fault protection was proposed, which criterion was made up of the instantaneous power asymmetry degree and its phase characteristic. The sensitivity and reliability of the novel generator asymmetry fault protection was high through the dynamic simulation test. Meanwhile the novel protection connection was simple, and it could be used complementarily with other protections.In order to solve the low power protection mal-operation problem of the pumped-storage synchronous machine when it was in the pumping condition, this paper studied the power swing characteristic and analyzed the mal-operation reasons of the low power protection. A novel multi-zone low power protection was proposed through the digital simulation and the field data analysis. The setting values of the multi-zone low power protection were matching with its delay values, which could adapt to the different stages of power oscillation.All research results were summarized finally and the direction of further research were pointed out.更多还原