Effect of controlling the sequential interruption of a system faulton turbine-generator shaft torsional torques

A new method is presented to reduce the high torsional torques induced in turbine-generator shafts during the clearing of multiphase faults. This method is based on controlling the sequential interruption of such faults. In this context, investigations have been conducted on two turbine-generator units of different designs for both three-phase and double line-to-ground faults. The effectiveness of the proposed method is illustrated through parametric studies and simulation results. The effects of the fault clearing time, the strength of the system to which the unit is connected, and the fault incidence instant on the effectiveness of the method have also been investigated     

Impact of six phase transmission line faults on turbine-generatorshaft torsional torques

This paper explores the impact of six-phase transmission line faults and their subsequent fault clearing and reclosing on the torsional torques induced in turbine-generator shafts. In this context, investigations have been conducted on a large turbine-generator unit connected to a sample power system. The paper presents also a comparison between the torsional stresses induced in the turbine-generator shafts during these events with their corresponding disturbances of a three-phase transmission system. The results of these investigations are presented in the form of typical time responses as well as parametric studies. The EMTP is used for the simulation studies. The studies conclude that six-phase transmission line faults generally induce torsional torques in the turbine-generator shaft whose magnitudes are relatively higher than those induced due to transmission line faults in a three-phase system. This conclusion is true for both sustained faults and faults followed by clearing and high-speed reclosing operations     

900 MW汽轮发电机组轴系扭振的研究

主要研究了上海外高桥电厂二期工程中的 2台 90 0 MW汽轮发电机组的轴系扭振及疲劳寿命损耗。轴系扭振模型采用集中参数等值模型 ,整个轴系分为 6段。计算结果表明 ,机组扭振频率避开了工频与倍频 ,轴系不会因共振而破坏。在短路故障时轴系扭振是安全的     

考虑水力和电磁激励的水电机组轴系统的扭转振动分析

推导了水轮发电机组的电磁力矩和电磁刚度的表达式,建立了考虑转子支臂刚度并在水力转矩和电磁力矩耦合作用下的轴系统机电耦联扭振模型。研究了轴系统扭振特性随转子转动惯量、支臂刚度、转轮水体附加质量的变化规律。分析了不同频率的水力激励对转子扭振响应的影响规律,得出了轴系最大扭矩内力、扭振角和电磁力矩的频响曲线。研究水力激励频率等于零频和一阶频率时的机电耦联共振特性,给出了激磁电流和内功率角对扭振的影响,揭示了机电耦联振动规律,为水电机组的设计与安全稳定运行提供理论依据。     

汽轮机配汽剩余汽流力对轴系影响的研究

给出了一个由调节级配汽剩余汽流力所引发的轴系故障的研究实例，这是一个在工程实践中未曾研究过的问题，故障现象表现为机组降负荷运行时，靠近调节级的各瓦轴振异常、瓦温升高甚至轴瓦烧蚀。故障产生机理的分析和实验数据的整理，对于解决同类故障和指导配汽设计具有参考意义。     

1000 MW汽轮发电机组轴系扭振特性的计算分析

对上海—西门子型1000 MW汽轮发电机组轴系的西门子技术模化形式进行了分析,根据扭振特性一致原则对西门子技术模化形式的轴系数据进行了等效转换,在此基础上对上海—西门子型1000 MW机组的扭振特性进行了计算分析。     

Effect of an excitation system on turbine-generator torsional stress in an HVDC power system

This paper deals with the impact of an excitation system on the torsion dynamics of turbine-generators, which are located on the inverter side of HVDC systems. Turbine-generator stress depends on the type and the parameters of an excitation system, and the fault type and location in an ac network because of commutation failures at the inverter station. Also, this paper analyzes how parameters of an excitation system are related to the torsional stress of a turbine-generator. Using the CIGRE benchmark model, the torsional stress on a generator on the inverter side is simulated. The PSCAD/EMTDC program is used for simulation studies.     

Identification of instantaneous attributes of torsional shaft signals using the Hilbert transform

A systematic analytical procedure based on the concept of the analytic signal (AS) of Gabor is used to determine the time-varying attributes of torsional oscillations, namely the instantaneous amplitude and the instantaneous frequency. Methods for implementing the AS using the numeric Hilbert transform are given and criteria for characterizing nonlinear effects are discussed. The proposed methodology is demonstrated on the IEEE First Benchmark Model (FBM) for subsynchronous resonance studies. The AS analysis is performed on output data files generated by nonlinear simulations using the EMTP, but the method is general and is applicable to any nonlinear, nonstationary signal. Numerical results include the determination of the instantaneous frequency of torsional oscillation signals following large perturbations. Comparison of numerical results obtained by the proposed method with linear analysis techniques is provided.     

自动重合器方向保护在中性点不接地系统中的应用

中性点不接地配电系统中使用自动重合器必须注意一些特殊要求。当相对地发生故障时,邻近馈线相对地之间会产生特别的容性故障电流,故所有配电网络需要配置检测故障方向的保护功能。图1使用自动重合器实例示意图如图1所示,R4重合器下游末端馈线发生一个故障,通过变电所的中压母线连接,导致邻近馈线内会有容性故障电流反方向流入故障点,如果R1、R2和R3不能检测潮流方向,这些重合器会误跳,给用户带来不必要的损失。最好的解决方案就是让R4重合器跳闸,其他重合器保持在合位。配备方向保护的重合器能够实现上述功能。当发生故障时,R1、R2和R3…     

Measurement of the transient electrical and shaft torques in an induction motor drive by the indirect two-speed method

Contents This paper presents a new method, called Indirect Two-Speed Method (ITSM), for obtaining electrical and shaft torques in an induction motor drive by means of measuring the speeds of both lumped-inertia elements assigned to a second order model. The measuring is realized by using high-resolution digital tachometers (represented by incremental encoders), two frequency measurement systems based on the Double-Buffered Method, digitalfiltering of the raw speed data and numerical differentiation of the filtered speed data.

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Messung transienter Drehmomente eines Induktionsmotor-Antriebs mittels der Indirekten Zwei-Drehzahlen-Methode

Übersicht Im Beitrag wird ein neues Verfahren zur Ermittlung des elektrischen Moments und des Wellen-Drehmoments eines Induktionsmotor-Antriebs vorgestellt. Das als Indirekte Zwei-Drehzahlen-Methode (ITSM) bezeichnete Verfahren geht aus von einem mechanischen Modell zweiter Ordnung und mißt die Drehzahlen beider als konzentrierte Parameter betrachteten Drehmassen. Für die Durchführung werden hochauflösende digitale Tachometer eingesetzt. Die Frequenzmessung erfolgt durch ein Verfahren mit doppelter Pufferung, und es werden die Rohdaten nach digitaler Filterung numerisch differenziert.

     

The damping effect of the flywheel dampers installed at different shaft couplings on torsional oscillations

This paper eamines the damping effect of flywheel dampers installed at different shaft couplings on torsional oscillations on the 951 MW turbine-generator shafts due to network faults. A studied system is described and torsional fatigue on the turbine shafts following various electrical system disturbances is analyzed and evaluated. Moreover, the influence of the safety factor selected and set at the design stage to the shaft life expenditure due to fatigue damage is also presented. Useful additional insight into their modes of operation is obtained from the fast Fourier transform of the transient response results. All computer simulations thus show that the proposed dampers are effective in suppressing the torsional oscillations on the shafts. In this paper, time-domain torque evaluation is also combined with the fast Fourier transform method to derive a selection procedure for obtaining suitable flywheel dampers to depress the amplitude of these critical shaft oscillations to acceptable levels.     

A fuzzy logic‐controlled SMES for damping shaft torsional oscillations of synchronous generator

This paper presents a fuzzy logic control scheme for the superconducting magnetic energy storage (SMES) based on a PWM voltage source converter and a two‐quadrant chopper using an insulated‐gate‐bipolar‐transistor (IGBT) to dampen turbine‐generator shaft torsional oscillations. Simulation results of balanced faults in a single machine connected to an infinite bus system show that the proposed fuzzy logic‐controlled SMES is effective in damping shaft torsional oscillations of synchronous generators (GENs). © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Steady‐state stability of shaft torsional oscillation in an ac‐dc interconnected system with self‐commutated converters

Recent progress in power electronics technology makes it possible to consider applying self‐commutated converters using gate turn‐off thyristors (GTOs) to HVDC transmission systems. Since the self‐commutated converter can be operated stably without depending on ac‐side voltage, the magnitude and the phase angle of the converter output voltage can be controlled independently. Therefore, this type of converter will improve voltage stability at its ac side. On the other hand, shaft torsional oscillation of a thermal power plant caused by the interaction between the shaft‐generator system and the control system of the self‐commutated converter is still an open problem. In this paper, a linearized model for eigenvalue analysis of a power system, including HVDC interconnection with self‐commutated converters, is described to analyze the effect of the self‐commutated converter on the shaft torsional oscillation of a thermal power plant. Then, numerical results from the eigenvalue analysis of the shaft torsional oscillation are presented. Results obtained by the frequency response method are also reported. The numerical results make it clear that parameter regions of DC‐AVR and ACR control systems of self‐commutated converters exist where the shaft torsional oscillation may be caused. © 1999 Scripta Technica, Electr Eng Jpn, 128(4): 25–37, 1999     

Reduced-order shaft system models of turbogenerators

Two very simple, sufficiently accurate reduced-order shaft system models, the truncated modal model and the aggregated mass model, used in turbogenerator torsional oscillation analysis are presented. The first is developed by taking the exact duplicate of the transient behavior of the original as far as the low-order modes are concerned, while the second is established by fitting the low-order mode shapes of the original. They can be implemented into existing programs without any difficulty, while the fidelity can easily be adjusted by changing their orders     

基于虚拟仪器技术的汽轮发电机组扭振测试系统

利用虚拟仪器技术设计和构建了扭振信号采集和分析系统的框架,开发了一种能有效测量和分析扭振的汽轮发电机组扭振测试系统。采用PXI数据采集系统实现了系统的硬件,采用LabVIEW图形化编程语言编制了系统的软件。系统利用汽轮发电机组机端的转速信号,使用零相位数字滤波器直接从转速信号中提取扭振分量。从扭振分量中分离出扭振模态并分析它们的特性。系统已多次应用于电厂的实际调试,实测数据分析显示,该扭振测试系统灵活易用,能满足实际应用的需求。     

变电站自动化系统常见故障及处理

针对自动化系统在现场实际运行中的常见故障:通信网络类故障、数据采集故障、误报警故障和与其他厂家装置不匹配故障进行了分析和归纳,从大量的现场数据中找出其规律性,分析了产生的原因(产品质量、不同厂家设备的接口通信、开放性等问题),提出了处理建议与改进措施.着重介绍了与变电站自动化系统密切相关几类典型问题的解决方法,为快速查找和正确处理变电站自动化系统故障提供了指导方法.     

变频器对风电系统轴电压和轴电流的影响

在现代风力发电系统作中,由于大量采用了高频电力电子器件,给整个系统带来了轴电流问题,严重影响着系统的安全运行和发电机轴承等机械部件寿命。精确分析发电机内部电容参数对准确预测轴电压和轴电流的重要作用。首先分析了风力发电系统的共模电路,通过研究风力发电机内部结构,确定了电机耦合电容的解析计算公式,同时提出了有限元计算方法。等效分析轴承运行过程中轴承等效电容模型,进而确定了风力发电机系统轴电流形成机理和影响因素。     

110 kV系统断路器控制回路断线引起重合闸不正常动作原因分析及改进措施探讨

在控制回路断线情况下,重合闸缺乏相应闭锁量,动作判据满足,将会不对应启动重合闸;通过介绍电力系统110 kV电压等级断路器控制回路断线后引起重合闸不正常动作的事例,结合分析重合闸功能的原理及相关外部回路设计,提出闭锁回路引入控制回路断线动断触点加延时,操作回路采用低气压闭锁重合闸,启动回路引入模拟合后继电器动合触点,或跳位动合触点串合后动断触点等可行方案,有效解决不同情况下的重合闸误动隐患.     

多相多边形无刷励磁机及旋转整流系统的运行状态分析

多相多边形无刷励磁机由于其固有的一些技术特点在一些大容量常规火电站和核电站中得到应用,对该励磁机整流系统运行状态的分析是研究其电气原理和特性的关键。基于多相多边形无刷励磁机电枢实际的空间分布与连接,得到了二极管的理想导通规律;进一步地,考虑换相过程中各阶段的二极管导通数量及等值电路,解析了各状态的电气量波形,获得了各导通状态所满足的临界条件;对一台十一相动模样机进行了实验研究,将实验结果与通过理论解析得到的二极管电流进行了对比,验证了理论分析的准确性。从而完整地揭示了多相多边形无刷励磁机及旋转整流系统的导通换相规律,为该系统的设计提供了理论依据。     

汽轮机轴系的状态检修

分析了汽轮机轴系状态检修的重要性,介绍一种新颖的"汽轮机轴系预测维修系统",给出了其硬件和软件。该系统在电厂实际运行中取得了很好的效果。