连锁故障阶段划分及破坏程度

为研究连锁故障的演化机理,调研分析了世界各国的大停电发展过程,针对连锁故障事故,给出了连锁故障不同发展过程的描述,阐述了连锁故障的不同阶段特点,提出了一种连锁故障的阶段划分方法,将连锁故障过程具体分为故障前阶段、初始故障阶段、慢演化阶段、快演化阶段以及崩溃阶段。在此基础上,考虑连锁故障对系统的破坏,提出了一种连锁故障破坏程度的量化指标,为连锁故障的阻隔提供参考。过IEEE118节点系统验证其合理性,结果表明,该方法可以较好地描述连锁故障的演化过程。破坏程度指标可以为连锁故障的阶段划分提供参考     

一起多点接地导致自闭/贯通线路故障跳闸案例分析

自闭贯通线路多是采用电缆架空混架的形式,线路中存在大量电缆和架空箱变,一旦线路线路发生故障跳闸,多是采用翻牌式故障指示器进行故障区间的确认,无法实现线路的精确定位。同时,基于现阶段自闭贯通线路的结构,在进行故障处理式,需要通过大量的人力进行巡线,对于自闭/贯通线路的故障处理极不友善。本文基于行波法故障测距理论,分析了现阶段自闭/贯通线路故障测距所面临的难题,同时对已安装了行波法故障监测装置的线路进行故障定位,成功定位了一起多点故障导致的自闭/贯通线路故障,从而排除了自闭/贯通线路故障。相比传统翻牌式故障指示器,行波故障监测装置大大提升了故障处理效率,从而大大提升了自闭/贯通线路自动化运维水平。     

基于聚类分析与加权模糊逻辑的汽轮机组振动故障诊断方法研究

针对汽轮机组振动故障诊断中故障征兆的使用问题,提出了一种基于聚类分析与加权模糊逻辑相结合的故障诊断方法。利用振动的频谱特征对振动故障的几种常见故障模式进行分类,形成故障模式类,从而可以在故障模式类层次区分开属于不同性质的故障模式,解决类间的识别问题,进而缩小故障模式的识别范围。对于同一故障类中的故障模式,采集不同类型的故障征兆,利用粗糙集理论建立故障诊断决策表,提取对故障识别有贡献的故障征兆构建故障诊断规则,再应用知识依赖度为故障诊断规则的前提条件分配权重,克服了主观分配权重存在的不足,减少了故障诊断推理过程中的不确定性影响。再应用加权模糊逻辑对故障诊断规则进行推理,根据推理结果对故障模式进行识别。该方法既充分利用了振动的频谱特征这一重要故障征兆作为故障诊断的初步判断依据,又综合利用了反映故障不同方面信息的不同类型的故障征兆,从而做到更加准确地进行故障识别。     

变压器外部故障切除后恢复性涌流的研究

分析了变压器从外部故障发生到被切除的电磁暂态全过程,提出了故障传递剩磁的概念,说明了变压器外部故障发生时刻电势相角、故障严重程度、故障持续时间和故障回路时间常数这四个参数对变压器可能出现恢复性涌流起决定作用.     

变电站电气设备故障类型分析与监测系统设计

深入分析了变压器、断路器等一次设备的故障类型和原因。从电气设备的故障监测背景出发,重点对变压器、断路器故障监测进行分析研究,并且给出了变压器的故障类型树。通过分析国内外近年来故障监测的发展状况,对变压器和断路器设计了故障监测系统,并分析了如何利用监测收集的数据对电气设备进行故障诊断,从而实现变电站故障的实时监测,防止电气设备故障的进一步扩大。     

电控共轨柴油机典型故障的原因及排除方法

分析了电控共轨柴油机的几种典型故障形式,如油路故障、电路故障及相位故障等,并具体阐述了每种故障的原因和排除方法。     

柴油机性能故障仿真及信息特征分析

介绍了柴油机性能故障的仿真模型和６２６０ Ｚ Ｃ柴油机１５ 种典型故障的仿真计算结果。通过对相同故障下热工参数的相对偏差分析和相同热工参数不同故障的绝对偏差分析,研究了热工参数对故障的敏感性和故障对热工参数的影响。对各种故障下热力参数的主成因分析,揭示了柴油机性能故障与热力参数之间的内在联系,提出了热力特征参量的优化选择方法和性能故障的分类方法,可以为人工神经网络的诊断应用提供训练学习样本。     

复杂配电网故障定位新矩阵算法

针对轨道交通复杂电网的多重故障问题,基于故障区域不存在流出该区域的故障过流的原理,提出了一种新的配电网故障定位算法,可对单一故障、复杂电网多重故障和馈线末端故障迅速做出定位,且在网络拓扑结构发生改变时算法的定位计算过程改变不大.并模拟计算了三电源配电网闭环运行时故障和轨交电网开闭环运行时故障.结果表明,该算法快速、有效...     

故障容错免疫系统

论述了故障容错技术研究的一般方法。为了拓宽故障容错技术研究的新途径,介绍了将人工免疫系统应用于故障容错技术研究的新方法——故障容错免疫系统。最后对故障容错免疫系统提出了一些可行的研究方向。     

基于正交最小二乘模型拟合的DPF故障诊断方法

根据柴油机颗粒过滤器(DPF)堵塞与泄漏故障型式开展了排气阻力试验和发动机台架试验,获取了排气流量、排气温度、排气压差等主要故障特征参数数据。通过与传统压降模型进行对比分析,将正交最小二乘方法应用于DPF的故障诊断,形成基于正交最小二乘模型拟合的DPF故障诊断方法,并用试验采集到的主要故障特征参数数据对模型拟合方法进行了可行性验证。通过定义一个错误系数向量,分析了广义故障空间中不同故障型式DPF所形成的故障区域,为DPF故障诊断技术的发展提供了理论依据。通过错误系数向量能够判断出故障程度及堵塞、泄漏等故障型式,基于该结果可以进行DPF故障诊断。     

汽轮发电机组振动故障诊断

本文提出了用于回转机械振动故障诊断的物理模型和数学模型。该数学模型可用于大型汽轮发电机组振动故障的诊断。     

200MW机组运行性能诊断的热经济学方法

在热经济学结构理论的基础上,讨论了热力系统运行性能诊断的热经济学方法,以200MW机组热力系统的计算模型为例,阐述了各部件及产品关系,建立了系统的热经济学生产模型,并对故障诊断的方法、故障引起的系统资源消耗增量进行了理论分析和实际计算,提出了具有较高灵敏度的故障判别指标,以及反映故障影响的量化指标,并针对具体算例进行了分析计算。     

计及实时老化状态的大型变压器本体绝缘故障率预测模型研究

故障率是电力系统中一项可靠性评估参数,通过故障率计算可靠性指标与设备故障损失对于电力系统的规划与电力系统的运行至关重要。为此,提出一种考虑老化失效的大型变压器本体绝缘故障率预测模型,即先建立变压器的温升老化失效模型,得到变压器实时的老化速率及运行状态;其次,建立多状态马尔可夫故障率预测模型,对变压器本体绝缘实时故障率进行预测;最后,利用比例故障率模型结合老化失效过程对变压器当前的状态转移速率进行修正,进而得到更加精确的变压器实时预测故障率。算例分析表明,通过老化失效模型对多状态马尔可夫故障率预测模型进行修正,能够更加精确地对变压器本体绝缘实时故障率进行预测。     

Optimal periodic inspection of a deterioration process with sequential condition states

The condition of components subject to visual inspections is often evaluated on a discrete scale. If at each inspection a decision is made to do nothing or to perform preventive or corrective maintenance, the proposed decision model allows us to determine the optimal time between periodic inspections, such that the expected average costs per unit of time are minimized. The model which describes the uncertain condition over time is based on a Markov process with sequential phases. The key quantities involved in the model are the probabilities of having to perform either preventive or corrective maintenance before or after an inspection. The costs functions for two scenarios are presented: a scenario in which failure is immediately detected without the need to perform an inspection and a scenario in which failure is only detected by inspection of the object. Analytical results for a special case and algorithmic results for a broad class of Markov processes are derived. The model is illustrated using an application to the periodic inspection of road bridges.     

Time dependent failure probability estimation of the solid oxide fuel cell by a creep-damage related Weibull distribution model

In present paper, a new model is proposed and embedded into the finite element software ABAQUS to estimate the time dependent failure probability of the solid oxide fuel cell stack. The results show that sealant is the potential failure region of the solid oxide fuel cell stack, while the failure probability of the anode, electrolyte and cathode are very small within the operation time of 50,000 h. The creep and damage distribution of the components reflect that the proposed model can reasonably predict the time dependent failure probability of the solid oxide fuel cell stack. Increasing either the characteristic strain, Weibull modulus or decreasing the operating temperature can decrease the failure probability of the SOFC stack. For the sealant, to ensure the high temperature integrity of the SOFC stack, the characteristic strain should be larger than 0.01 or Weibull modulus should be higher than 8.0 under the operating temperature of 600 °C.     

某深孔平面钢闸门失事原因分析

针对某水电站深孔平面钢闸门在运行过程中损坏的问题,考虑流固耦合作用,建立闸门与水体三维有限元模型,分析了闸门自振特性及动力响应,探讨了闸门失事原因。结果表明,闸门的一阶频率与水流脉动主频较接近,有发生共振的可能;动水作用下,闸门部分构件出现了较大的位移与应力,超过了规范容许最大值。闸门失事可能由振动破坏、强度破坏等原因导致,研究结果为平面钢闸门的工程设计和应用提供了参考。     

A study of solid oxide fuel cell stack failure by inducing abnormal behavior in a single cell test

It is well known that cell imbalance can lead to failure of batteries. Prior theoretical modeling has shown that similar failure can occur in solid oxide fuel cell (SOFC) stacks due to cell imbalance. Central to failure model for SOFC stacks is the abnormal operation of a cell with cell voltage becoming negative. For investigation of SOFC stack failure by simulating abnormal behavior in a single cell test, thin yttria-stabilized zirconia (YSZ) electrolyte, anode-supported cells were tested at 800 °C with hydrogen as fuel and air as oxidant with and without an applied DC bias. When under a DC bias with cell operating under a negative voltage, rapid degradation occurred characterized by increased cell resistance. Visual and microscopic examination revealed that delamination occurred along the electrolyte/anode interface. The present results show that anode-supported SOFC stacks with YSZ electrolyte are prone to catastrophic failure due to internal pressure buildup, provided cell imbalance occurs. The present results also suggest that the greater the number of cells in an SOFC stack, the greater is the propensity to catastrophic failure.     

A model of district heating using a CHP plant

The paper presents a static linear programming model of a district heating system in which the base load is covered by a cogenerating station producing heat and electricity. The model provides optimal investment decisions (generating station, hot water accumulator, peak units, distribution network) as well as optimal operating rules. The reliability of the cogenerating station is taken explicitly into account by introducing shortage costs in case of failure. It is assumed the electricity produced is sold at time-variable transfer prices to the public grid. Numerical results are provided for a medium-size city.     

Pipe segment failure dependency analysis and system failure probability estimation

The present paper is mainly concerned with pipe-system failure probability estimation. For this purpose, a multiple component dependent failure (MCDF) model is introduced to deal with dependency among pipe-segment failures. The MCDF model is directly derived from load–strength interference analysis with the underlying notion that stochastic environment load brings about failure dependency. The influence of pipe-segment failure dependency on pipe-system failure probability is addressed and a modified system failure probability model is presented. It is also shown that, with regard to a pipe system, the multiple failures of pipe-segment leaks might lead to a pipe-system disabling leak or even to a break. The probability of a pipe-system disabling leak or break induced by the simultaneous failures of multiple segment leaks is estimated by means of the MCDF model. The estimation results indicate that pipe-system failure probability depends not only on the mean values of the respective segment-failure probability random variables, but also on other distribution parameters (e.g., the standard deviations) of them. Pipe-system failure probability estimated by means of the modified model is sometimes several times lower than that estimated by the conventional system failure probability model.     

Hazard Model Reliability Analysis Based on a Wind Generator Condition Monitoring System

This paper presents an application of the hazard model reliability analysis on wind generators, based on a condition monitoring system. The hazard model techniques are most widely used in the statistical analysis of the electric machine＇s lifetime data. The model can be utilized to perform appropriate maintenance decision-making based on the evaluation of the mean time to failures that occur on the wind generators due to high temperatures. The knowledge of the condition monitoring system is used to estimate the hazard failure, and survival rates, which allows the preventive maintenance approach to be performed accurately. A case study is presented to demonstrate the adequacy of the proposed method based on the condition monitoring data for two wind turbines. Such data are representative in the generator temperatures with respect to the expended operating hours of the selected wind turbines. In this context, the influence of the generator temperatures on the lifetime of the generators can be determined. The results of the study can be used to develop the predetermined maintenance program, which significantly reduces the maintenance and operation costs.