Fault Type Analysis along the San Andreas Fault Zone: A Numerical Approach

Finite Element (FE) modeling under plane stress condition is used to analyze the fault type variation with depth along and around the San Andreas Fault (SAF) zone. In this simulation elastic rheology was used and was thought justifiable as the variation in depth from 0.5 km to 20 km was considered. Series of calculations were performed with the variation in domain properties. Three types of models were created based on simple geological map of California, namely, 1) single domain model considering whole California as one homogeneous domain, 2) three domains model including the North American plate, Pacific plate, and SAF zone as separate domains, and 3) Four domains model including the three above plus the Garlock Fault zone. Mohr-Coulomb failure criterion and Byerlee's law were used for the calculation of failure state. All the models were driven by displacement boundary condition imposing the fixed North American plate and Pacific plate motion along N34°W vector up to the northern terminus of SAF and N50°E vector motion for the subducting the Gorda and Juan de Fuca plates. Our simulated results revealed that as the depth increased, the fault types were generally normal, and at shallow depth greater strike slip and some thrust faults were formed. It is concluded that SAF may be terminated as normal fault at depth although the surface expression is clearly strike slip.

Review of Fault Types, Impacts, and Management Solutions in Smart Grid Systems

Fault management study in smart grid systems (SGSs) is important to ensure the stability of the system. Also, it is important to know the major types of power failures for the effective operation of the SGS. This paper reviews diverse types of faults that might appear in the SGS and gives a survey about the impact of renewable energy resources (RERs) on the behavior of the system. Moreover, this paper offers different fault detection and localization techniques that can be used for SGSs. Furthermore, a potential fault management case study is proposed in this paper. The SGS model in this paper is investigated using both of the Matlab/Simulink and the Real Time Digital Simulation (RTDS) to compute the fault management study. Simulation results show the fast response to a power failure in the system which improves the stability of the SGS.

A novel controllable crowbar based on fault type protection technique for DFIG wind energy conversion system using adaptive neuro-fuzzy inference system

This paper proposes a novel controllable crowbar based on fault type(CBFT)protection technique for doubly fed induction generator(DFIG)wind energy conversion system connected to grid.The studied system consists of six DFIG wind turbines with a capacity of 1.5 MW for each of them.The operation mechanism of proposed technique is used to connect a set of crowbar resistors in different connection ways via activation of controllable circuit breakers(CBs)depending on the detected fault type.For each phase of DFIG,a crowbar resistor is connected in parallel with a controllable CB and all of them are connected in series to grid terminals.The adaptive neuro-fuzzy inference system(ANFIS)networks are designed to detect the fault occurrence,classify the fault type,activate the CBs for crowbar resistors associated with faulted phases during fault period,and deactivate them after fault clearance.The effectiveness of proposed CBFT protection technique is investigated for different fault types such as symmetrical and unsymmetrical faults taking into account the single-phase to ground fault is the most frequently fault type that occurs in power systems.Also,a comparison between the behaviours of studied system in cases of using traditional parallel rotor crowbar,classical outer crowbar,and proposed CBFT protection techniques is studied.The fluctuations of DC-link voltage,active power,and reactive power for studied system equipped with different protection techniques are investigated.Moreover,the impacts of different crowbar resistance values on the accuracy of proposed technique are studied.The simulation results show that,the proposed technique enhances the stability of studied wind turbine generators and contributes in protection of their components during faults.

Coordinated Rotor-Side Control Strategy for Doubly-FedWind Turbine under Symmetrical and Asymmetrical Grid Faults

In order to solve the problems of rotor overvoltage,overcurrent and DC side voltage rise caused by grid voltage drops,a coordinated control strategy based on symmetrical and asymmetrical low voltage ride through of rotor side converter of the doubly-fed generator is proposed.When the power grid voltage drops symmetrically,the generator approximate equation under steady-state conditions is no longer applicable.Considering the dynamic process of stator current excitation,according to the change of stator flux and the depth of voltage drop,the system can dynamically provide reactive power support for parallel nodes and suppress the rise of DC side voltage and rotor over-current.When the grid voltage drops asymmetrically,the positive and negative sequence components are separated in the rotating coordinate system.The doubly fed generator model is established to suppress the rotor positive sequence current and negative sequence current respectively.At the same time,the output voltage limit of the converter is discussed,and the reference value is adjusted within the allowable output voltage range.In order to adapt to the occurrence of different types of power grid faults and complex operating conditions,a fast switching module of fault type detection and rotor control mode is designed to detect the type of power grid faults and voltage drop depth in real time and switch the rotor side control mode dynamically.Finally,the simulation model of the doubly fed wind turbine is constructed in Matlab/Simulink.The simulation results verify that the proposed control strategy can improve the low-voltage ride through performance of the system when dealing with the symmetrical and asymmetric voltage drop of the power grid and identify the power grid fault type and provide the correct control strategy.

Study on inelastic displacement ratio spectra for near-fault pulse-type ground motions

In displacement-based seismic design, inelastic displacement ratio spectra (IDRS) are particularly useful for estimating the maximum lateral inelastic displacement demand of a nonlinear SDOF system from the maximum elastic displacement demand of its counterpart linear elastic SDOF system. In this study, the characteristics of IDRS for near-fault pulse-type ground motions are investigated based on a great number of earthquake ground motions. The in? uence of site conditions, ratio of peak ground velocity (PGV) to peak ground acceleration (PGA), the PGV, and the maximum incremental velocity (MIV) on IDRS are also evaluated. The results indicate that the effect of near-fault ground motions on IDRS are signifi cant only at periods between 0.2 s - 1.5 s, where the amplifi cation can approach 20%. The PGV/PGA ratio has the most signifi cant in? uence on IDRS among the parameters considered. It is also found that site conditions only slightly affect the IDRS.

塔里木盆地北部奥陶系海相碳酸盐岩断溶体油藏成因类型及特征再认识

前人提出的“断溶体”油藏概念,现已成为海相碳酸盐岩油气藏勘探开发的新目标、新类型。但断溶体油藏与传统的风化壳型喀斯特油藏有显著差别,断溶体储集体类型、结构特点也存在差异。研究断溶体溶蚀作用和构造破裂作用的差异性,将断溶体划分为过溶蚀残留型、破碎+强溶蚀型和强破碎+弱溶蚀型3种类型。研究表明不同成因类型的断溶体油藏,其溶蚀程度、缝洞规模、累产油量、地层能量和缝洞间连通性差异明显。过溶蚀残留型油藏的分布受风化壳不整合面及断裂带的纵向溶蚀作用控制。破碎+强溶蚀型及强破碎+弱溶蚀型油藏的形成和分布与不整合面的发育和构造位置关系不大,主要受溶蚀断裂带“破碎+溶蚀程度”控制,在溶蚀断裂带核部发育规模较大的洞穴,向两侧逐步发育裂缝-孔洞型、裂缝型储层。

近断层脉冲型地震作用下大跨拱桥动力响应分析

为了研究近断层脉冲型地震动的速度脉冲特性和参数对大跨拱桥动力响应的影响规律,首先引入分解叠加(record-decomposition incorporation,RDI)法合成人工近断层脉冲型地震动,对比研究了不同等效脉冲模型的准确性,进而优化和验证了合成方法;然后以某大跨拱桥为工程背景,采用优化后的RDI方法合成了具有不同参数特征的人工近断层地震动,探讨了脉冲成分与残余分量对拱桥动力响应的影响机制;最后研究了不同脉冲参数对拱桥动力响应的影响规律。研究表明:优化后的RDI合成方法能有效模拟原始近断层脉冲型地震动,并得到具有不同脉冲参数的人工地震动;近断层地震记录的高频成分对拱桥结构动力响应具有显著的不利影响;随着脉冲幅值的增大,向前方向性效应和滑冲效应对拱桥动力响应的影响均明显增大;随着脉冲周期的增大,两种脉冲效应对拱桥动力响应均有显著的不利影响;对于脉冲个数的影响,双向脉冲的近断层地震动相比多向脉冲会引起拱桥更大的面内响应。

塔里木盆地富满断控破碎体油藏储集类型特征与注水替油效果

塔里木盆地走滑断裂控制的超深油气藏是近年来中国油气勘探开发最重要领域之一,但目前该类型油藏的储集空间类型并不清楚,不同储集空间类型与注水效果关系不明确,严重制约了富满油田的高效开发。在充分分析野外露头、岩心、成像测井以及动态监测资料的基础上,系统剖析了断控破碎体的3种主要储集空间类型及其与注水效果的关系。提出了断控破碎体的概念,指出富满油田主要为断控破碎体油藏,研究结果表明:①断裂空腔型储集体主要分布在断裂带的核部,由断层滑动面产状变化引发内部体积调整形成了“空腔”型洞穴。埋藏条件下的储集空间相对较为封闭,内部孔隙空间较大,注水后原油置换率较高,部分油井动用储量的注水采收率可高达93%。②角砾间孔隙型储集体主要分布在断裂带的核部,由相邻的角砾相互支撑而形成角砾间不规则储集空间类型。该类储集体分布较为均匀,孔隙度中等,单位压降下的产液量较高,但是由于储集空间内部连接并不通畅,注水后置换率较低,需要研究探索构建立体结构井网来提高开发效果。③构造裂缝型储集体主要分布在断裂带的损伤带和过程带,在断层带的两侧和端部发育形成一定宽度的裂缝带。裂缝带周边也会发育少量孔隙,部分区域会形成一定的渗流优势通道,因此注入水的流失量较大,注水效果相对于断裂空腔型储集体较差。研究成果支撑了富满油田上产原油350×10^(4) t,可助推注水开发方案和提高采收率方案的优化,对同类型油藏高效开发具有重要的借鉴意义。

矿用干式变压器故障诊断和寿命预测技术现状及展望

干式变压器故障诊断技术通过对监测数据进行分析,能够实现信号特征提取、故障诊断、状态评估和寿命预测,提高干式变压器在井下运行的安全性,降低由于故障带来的损失。文章介绍了信号特征提取方法(频率响应法、小波变换法、堆叠自编码器)、故障诊断方法(贝叶斯网络、支持向量机、BP神经网络)、状态评估和寿命预测方法(交叉熵组合预测法、灰色理论、层次分析法)的研究现状,将几种方法进行对比,并对干式变压器故障诊断技术进行展望。

航空发动机燃油控制装置可靠性研究综述

航空发动机燃油控制装置是航空发动机的核心控制单元,长期服役在高温、高压、强振的恶劣环境,在航空发动机外场使用中故障率占比高,产品的寿命及可靠性是当前制约我国装备能力提升的短板。本文总结了当前燃油控制装置的典型故障类型,对比分析了国内外在燃油控制装置可靠性设计与分析技术、可靠性优化技术、寿命试验技术及可靠性评估技术方面的研究进展;剖析了我国燃油控制装置可靠性技术研究及应用方面的不足及原因,同时结合航空发动机正向研发体系建设需要,指出了航空发动机自主创新设计中燃油控制装置性能及可靠性一体化设计所面临的技术难点和挑战,并立足于现有国内设计水平及工业基础,给出了夯实我国航空燃油控制装置设计能力需开展的基础性研究建议。

顺北地区断控缝洞体测井响应特征和类型识别方法

顺北地区断控缝洞体蕴藏有丰富的油气资源,断裂带控制了油气运移和聚集。断裂带结构复杂,发育断层、裂缝等多种储集空间,断层中充填不同物质。多种类型的储集空间和充填物导致常规测井响应复杂,加之研究区测井资料不尽相同,断控缝洞体类型识别困难。依据录井和电成像测井等信息,确定了未充填断裂洞穴型、角砾充填断裂洞穴型、泥质充填断裂洞穴型和裂缝型4种断控缝洞体类型。分析了单井测井资料,包括各种测线曲线、无密度测井曲线、无密度和无能谱测井曲线、无密度和无中子测井曲线、无密度和无中子以及无能谱测井曲线和无中子和无能谱测井曲线共6种情况。对比不同类型断控缝洞体的自然伽马、无铀伽马、声波时差、中子、密度、深侧向和浅侧向电阻率等测井响应差异,将测井响应两两组合进行交会分析,优选出5个对断控缝洞体类型敏感的测井响应交会图版,结合不同的测井资料情况,形成4套逐级识别断控缝洞体类型的流程,建立了一种利用常规测井资料识别断控缝洞体类型的方法。应用该方法对顺北地区实际井资料进行处理解释,识别结果与岩心、电成像测井解释结论一致。该识别方法能满足研究区各种测井曲线资料情况的断控缝洞体类型识别需求,识别结果为断裂带内部结构解释提供有效支撑。

基于混合威布尔模型的智能电能表可靠性评价方法

针对当前智能电能表故障类型多样、可靠性评价单一的问题,提出基于混合威布尔模型的可靠性评价方法。论文基于智能电能表各单元串联关系和故障事件进行故障类型分类,利用最小二乘法推算各单元故障类型的尺度与形状参数,结合中位秩与平均秩次计算智能电能表累计失效概率提高模型准确度,并通过熵权法计算各故障类型对整表可靠度影响的权重系数,据此建立基于混合威布尔模型的智能电能表可靠性评价方法。实例结果表明,提出的方法在各类故障类型下均能准确得到智能电能表可靠度评估,并能准确获得智能电能表单元模块的可靠度,与现有方法相比,文中方法不需大量先验知识,且实现简单、准确度更高。

低信噪比地震数据图像结构引导去噪方法与应用

地震噪声影响着复杂断裂结构与储层的刻画,有效压制噪声并保留地震资料中的结构信息,是解释性处理的关键。基于保边光滑原理,在地震数据处理中提出并引入图像结构引导滤波方法,实现自适应地保留断层、裂缝以及储层反射等关键信息并有效压制散射与随机噪声,提高地震数据信噪比。正演模拟数据的去噪试验结果表明,相比常规滤波方法,图像结构引导滤波方法具有更好的保边光滑特性;与构造导向滤波方法相比,该方法不需显式提取层位走向和倾角信息,具有较高的计算效率。实际三维资料的应用结果表明,该方法能有效压制不同类型噪声、提高信噪比和有效反射同相轴的连续性;处理后对应的相干属性可有效增强断裂、储层的分辨能力,更好地描述断裂系统的展布,有利于后续地震资料解释工作。

基于光纤传感器的大型风电机组叶片荷载在线监测方法

现阶段,风电机组得到深层次开发和运用,向低成本、高功率方向发展,机组风轮直径、扫琼面积不断增加,有效加快电力输送效率,满足社会的用电需求,但也提高运行隐患,极易出现叶片荷载不均匀的现象,影响大型风电机组的发电效果。该文以提高风电机组的发电稳定性为研究目标,着重阐述光纤传感器下大型风电机组叶片荷载在线监测系统,并简单论述叶片结构和受力分析,以及常见故障类型等内容,希望对相关研究工作有所参考。

基于ICEEMDAN与BiLSTM的交直流混联电网故障识别

针对交直流混联电网故障特征提取困难与故障类型识别准确率低的问题,提出了一种基于改进的完全自适应噪声集合经验模态分解(ICEEMDAN)和蜜獾算法优化双向长短时记忆神经网络(BiLSTM)超参数的交直流混联电网故障类型辨识方法。首先,利用ICEEMDAN对线路故障电压电流进行分解;然后,基于方差贡献率与相关系数联合特征指标选择模态分量并求其峰峰值,以选出的模态分量的峰峰值作为特征向量输入至蜜獾算法优化后的双向长短时记忆网络进行故障类型辨识。最后,在PSCAD/EMTDC中搭建了交直流混联电网模型对所提方法进行验证。实验结果表明,所提算法故障辨识准确率达到99.5%,受不同故障线路、故障过渡电阻、故障位置、数据丢失影响较小,并且对10 dB噪声干扰下的含噪声信号的故障辨识准确率达到95.9%,具有较强的适应性。

数字电视发射机故障分析与检修

围绕数字电视发射机的工作原理、常见故障类型及其检修方法进行深入探讨,旨在为相关人员提供借鉴。首先,介绍了数字电视发射机的工作原理。其次,详细分析了数字电视发射机中常见的硬件故障及软件故障,如功率放大器故障、调制器故障及供电系统故障。最后,提出了相应的故障检修方法。

基于扩展Type-2模糊集的故障检测方法

随着系统复杂程度的不断提高,对系统故障的诊断也越来越困难。提出一种扩展的Type-2模糊集合,利用扩展隶属函数的"肯定证据,排除假象"的特性,建立基于Type-2的模糊诊断方法,并给出了相应的设计算法。增加了负值的扩展隶属函数,将系统输出的残差清晰地划分为三个状态:正常、异常和故障。增加了一个状态,能够更好地得出清晰的诊断结果,有效地避免误诊和漏诊。针对三水箱系统,仿真结果表明了该方法的有效性。

矿井掘进机液压系统故障分析探讨

针对煤矿井下掘进机运转过程中液压系统故障频发的状况,本文通过分析各液压系统的组成及功能,对造成液压系统故障的原因进行类型划分,即划分为机械原因和人为原因。结合维修人员素质、现场条件提出了经验判断法、系统分析法和综合判断法等进行掘进机故障分析,为掘进机液压系统维修提供了多种维修思路,提高了液压设备维修效率。