基于动态模糊关联规则推理的光网络故障管理(英文)

当代光网络趋于复杂化,一个故障将引发多个告警事件。同时,同一告警可能由不同的故障导致。本文研究了基于数据挖掘的光网络告警相关性分析,我们从动态网络资源与设备中挖掘关联规则,充分利用和维护原有规则知识,使网络结构和规则库都能快速更新,并提出了新型的动态模糊关联规则挖掘算法IDFARM。同时运用模糊逻辑将数值型告警属性转化为逻辑语言变量,当网络中有新的未知告警发生时,我们对模糊关联规则运用模糊推理来进行故障诊断,这将缩短网络恢复时间,有利于提高光网络故障管理性能。仿真实验验证了文章算法的正确性和有效性。     

Simplified probabilistic selectivity technique for earth fault detection in unearthed MV networks

A novel selectivity technique to identify the faulty feeder in unearthed Medium Voltage (MV) networks is introduced. The proposed technique is based on a simplified probabilistic method applied to transient features extracted from the residual currents only using the discrete wavelet transform (DWT). DWT will enhance the accuracy of localising fault events with different fault resistances and the probability will give the protection decision (detection/selectivity). The standard deviation of a window of the DWT detail coefficient is used to detect the fault and an adaptive threshold is used as input to the probability function to estimate the faulty feeder. A faulty unearthed 20 kV network is simulated by ATP/EMTP imitating practical fault cases such as arcing and tree leaning faults. The time-domain test cases provide evidence of the efficacy of the proposed technique.     

Coded-orthogonal frequency division multiplexing in hybrid optical networks

Future Internet should be able to support a wide range of services containing large amount of multimedia over different network types at a high speed. The future optical networks will therefore be hybrid, composed of different single-mode fibre (SMF), multi-mode fibre (MMF) and free-space optical (FSO) links. In these networks, novel modulation and coding techniques are needed that are capable of dealing with different channel impairments, be it in SMF, MMF or FSO links. The authors propose a coded-modulation scheme suitable for use in hybrid FSO - fibre-optics networks. The proposed scheme is based on polarization-multiplexing and coded - orthogonal frequency division multiplexing (OFDM) with large girth quasi-cyclic low-density parity-check (LDPC) codes as channel codes. The proposed scheme is able to simultaneously deal with atmospheric turbulence, chromatic dispersion and polarisation mode dispersion (PMD). With a proper design for 16-quadrature amplitude modulation (QAM)-based polarisation-multiplexed coded-OFDM, the aggregate data rate of 100 Gb/s can be achieved for OFDM signal bandwidth of only 12.5 GHz, which represents a scheme compatible with 100 Gb/s per wavelength channel transmission and 100 Gb/s Ethernet.     

Decision tree-based fault zone identification and fault classification in flexible AC transmissions-based transmission line

Transmission line distance relaying for flexible AC transmission lines (FACTS) including thyristor controlled series compensator (TCSC), STATCOM, SVC and unified power flow controller (UPFC) has been a very challenging task. A new approach for fault zone identification and fault classification for TCSC and UPFC line using decision tree (DT) is presented. One cycle post fault current and voltage samples from the fault inception are used as input vectors against target output dasia1psila for fault after TCSC/UPFC and dasia0psila for fault before TCSC/UPFC for fault zone identification. Similarly, the DT-based classification algorithm takes one cycle data from fault inception of three phase currents along with zero-sequence current and voltage, and constructs the optimal DT for classifying all ten types of shunt faults in the transmission line fault process. The algorithm is tested on simulated fault data with wide variations in operating parameters of the power system network including noisy environment. The results indicate that the proposed method can reliably identify the fault zone and classify faults in the FACTs-based transmission line in large power network.     

Accurate Fault Location Modeling for Parallel Transmission Lines Considering Mutual Effect

A new accurate algorithms based on mathematical modeling of two parallel transmissions lines system (TPTLS) as influenced by the mutual effect to determine the fault location is discussed in this work. The distance relay measures the impedance to the fault location which is the positive-sequence. The principle of summation the positive-, negative-, and zero-sequence voltages which equal zero is used to determine the fault location on the TPTLS. Also, the impedance of the transmission line to the fault location is determined. These algorithms are applied to single-line-to-ground (SLG) and double-line-to-ground (DLG) faults. To detect the fault location along the transmission line, its impedance as seen by the distance relay is determined to indicate if the fault is within the relay’s reach area. TPTLS under study are fed from one- and both-ends. A schematic diagrams are obtained for the impedance relays to determine the fault location with high accuracy.     

New differential protection scheme for tapped transmission line

The development of a new differential protection scheme for tapped transmission lines using wavelet transform is presented. At each relay locations, using the most suitable mother wavelet, the measured three line currents are decomposed up to third level. Thereafter, third-level approximation coefficients are reconstructed and used to derive the operating and restraining quantities. The proposed scheme has been tested extensively using the PSCAD/EMTDC software package with fault data, generated by modelling UKAI-KAKRAPAR 400 kV line of the Indian power system. The proposed scheme eliminates many of the problems encountered with tapped transmission lines such as high resistance faults, out feed current in case of internal and external faults, insufficient current for tripping and provides better discrimination between external and internal faults in case of loss of generation at one end. At the end, a comparative evaluation of the conventional current differential protection scheme with the proposed scheme is also presented. Dependability and security have been studied separately.     

Error correction in bit‐sliced systems with redundancy in time

Abstract

A new error correction scheme for bit‐sliced arithmetic processors is presented. The method adopted for fault location is an extension of a concurrent error detection scheme named RESO (recomputing with shifted operands). The proposed scheme requires two consecutive computation steps for normal operations and the possible locations of faults, if any, can be located provided that the failures are confined to a certain number of adjacent bit‐slices. We can thus figure out those bit‐slices which are definitely fault‐free. Recomputation is then carried out through these fault‐free bit‐slices and a correct computation can be resulted. A design of the control circuitry as well as the switching mechanism is introduced. The assumption that the failures are confined to a small area of an integrated circuit and the precise nature of the failure is not known makes this scheme very attractive to VLSI circuits.     

自适应聚类Hough变换及地震断层检测

针对现有基于Hough变换的地震断层检测方法只能检测单个断层,不能准确检测多个断层的不足,提出了一种基于自适应聚类Hough变换的地震断层检测方法。该方法首先对预处理后的地震相干图像进行边缘检测并对边缘图像进行Hough变换以检测出边缘图像中的线段,然后根据倾斜角和位置信息对线段进行自适应聚类以获得更完整的线段,最后根据初始地震图像对完整线段中的各点进行调整以获得准确、平滑的断层。为验证该方法的有效性,在实际地震图像上进行了对比实验。实验结果表明,该方法可正确检测地震图像中的多个断层,正确率达到90%以上,与现有方法相比,峰值信噪比提高了约10%。     

基于遗传算法和BP神经网络的多联机阀类故障诊断

针对多联机系统(变制冷剂流量系统)阀类故障的诊断特征变量冗杂、诊断效率低的问题,提出一种复合诊断模型,利用遗传算法在原始特征集中搜索特征子集,与参数优化后的BP神经网络模型结合,对多联机阀类故障进行检测和诊断。本文从原始特征集中优化选择了带有18个特征变量的最优特征子集,用该模型对电子膨胀阀卡死、电子膨胀阀泄漏和四通阀故障3种故障进行检测,结果表明:该复合诊断模型对故障检测率提高,其中电子膨胀阀的卡死故障检测率提升8%,整体诊断正确率提高到99.27%;该复合诊断模型大大提高了诊断效率,使测试时间缩短了52.17%,表明该复合诊断模型具有较好的故障诊断效果。     

Differential equation-based fault locator for unified power flow controller-based transmission line using synchronised phasor measurements

The fault location algorithm based on a differential equation-based approach for a transmission line employing a unified power flow controller (UPFC) using synchronised phasor measurements is presented. First, a detailed model of the UPFC and its control is proposed and then, it is integrated into the transmission system for accurately simulating fault transients. The method includes the identification of fault section for a transmission line with a UPFC using a wavelet-fuzzy discriminator. Features are extracted using a wavelet transform and the normalised features are fed to the fuzzy logic systems for the identification of fault section. After the identification of the fault section, the control shifts to the differential equation-based fault locator that estimates the fault location in terms of the line inductance up to the fault point from the relaying end. Shunt faults are simulated with wide variations in operating conditions and a pre-fault parameter setting. The instantaneous fault current and voltage samples at the sending and receiving ends are fed to the designed algorithm sample by sample, which results in the fault location in terms of the line inductance. The proposed method is tested for different fault situations with wide variations in operating conditions in the presence of a UPFC.     

Bandwidth allocation in Diffserv-enabled ethernet passive optical networks

Ethernet passive optical networks (EPONs) have attracted considerable attention from the industry, as they offer a simple, highly flexible and cost-effective solution to the problem of providing broadband access to a customer. The authors present a new approach to bandwidth allocation in EPONs where the optical line terminator (OLT) has full control over the access mechanism. This results in much simpler optical network unit (ONU) architecture. It is shown that such an OLT-centric architecture offers full support for differentiated services and makes enforcement of service level agreements possible. Extensive simulation experiments show that bandwidth allocation algorithms deployed in such a centralised environment can deliver good performance in terms of average and maximum packet delay. The authors introduce two new algorithms that target SLA-aware EPONs and provide a good protection of offered quality of service against interference from other sources.     

Differential diagnosis of spall versus cracks in the gear tooth fillet region

This paper presents a technique to differentially diagnose two localized gear tooth faults: a spall and a crack in the gear tooth fillet region. These faults could have very different prognoses, but existing diagnostic techniques only indicate the presence of local tooth faults without being able to differentiate between a spall and a crack. The effects of spalls and cracks on the behavior/response of gear assemblies were studied using static and dynamic simulation models. Changes in the kinematics of a pair of meshing gears due to a gear tooth root crack and a tooth flank spall were compared using a static analysis model. The difference in the variation of the transmission error caused by the two faults reveals their characteristics. The effect of a tooth crack depends on the change in stiffness of the tooth, while the effect of a spall is predominantly determined by the geometry of the fault. The effect of the faults on the gear dynamics was studied by simulating the transmission error in a lumped parameter dynamic model. A technique had previously been proposed to detect spalls, using the cepstrum to detect a negative echo in the signal (from entry into and exit from the spall). In the authors’ simulations, echoes were detected with both types of fault, but their different characteristics should allow differential diagnosis. These concepts are presented prior to experimental validation in hopes that the diagnostic techniques will be useful in the failure analysis community prior to the validation by ongoing experimental testing of the concepts and the evaluation of how metallurgical defects may influence fault development and detection.     

Completely passive method of speckle reduction utilizing static multimode optical fibre and two-dimensional diffractive optical element

ABSTRACT

In this paper, we present experimental results on speckle noise suppression using a completely passive method. The passivity of the method is achieved owing to the absence of any mechanical, electronic, or other dynamic influences on the optical scheme elements. In the experiment, a multimode semiconductor 520?±?5-nm laser with a spectral bandwidth of 2?nm, static two-dimensional (2D) and 2?×?1D diffractive optical elements (DOEs), as well as multimode single-core optical fibre and multimode optical fibre bundle were used. The dependence of the speckle reduction efficiency as a function of the optical fibre type and optical fibre length was measured for different DOEs. A speckle contrast of 0.148 and speckle reduction coefficient of 2.38 were obtained for a 2.5-m-long multimode optical fibre bundle. The experimental results confirmed that it is possible to construct completely passive optical circuits with reduced speckle noises using static multimode optical fibres and diffraction optical elements.     

New approach to adaptive single pole auto-reclosing of power transmission lines

In this study, a novel digital algorithm is introduced for recognition of arcing (transient) faults and determination of dead time for adaptive auto-reclosing. The algorithm distinguishes between arcing and permanent faults by using the zero sequence voltage measured at the relaying point. If the fault is recognised as an arcing fault, then the third harmonic of the zero sequence voltage is used to evaluate the extinction time of secondary arc and to initiate reclosing signal. The proposed algorithm uses an adaptive threshold level and therefore no significant adjustment is needed for different transmission systems. Moreover, its performance is independent to fault location, line parameters and the system pre-fault operating conditions. The algorithm has been successfully tested for various faults and operating conditions on a 400 kV overhead line using the electro-magnetic transient program (EMTP). The test results have demonstrated validity of the algorithm in determining the secondary arc extinction time and blocking unsuccessful automatic reclosing during permanent faults.     

The design of reliable devices for mission-critical applications

Mission-critical applications require that any failure that may lead to erroneous behavior and computation is detected and signaled as soon as possible in order not to jeopardize the entire system. Totally self-checking (TSC) systems are designed to be able to autonomously detect faults when they occur during normal circuit operation. Based on the adopted TSC design strategy and the goal pursued during circuit realization (e.g., area minimization), the circuit, although TSC, may not promptly detect the fault depending on the actual number of input configurations that serve as test vectors for each fault in the network. If such a number is limited, although TSC it may be improbable that the fault is detected once it occurs, causing detection and aliasing problems. The paper presents a design methodology, based on a circuit re-design approach and an evaluation function, for improving a TSC circuit promptness in detecting faults' occurrence, a property we will refer to as TSC quality.     

Modular Neural Network Architecture for Precise Condition Monitoring

Unplanned production shutdown due to equipment failure is the source of the highest cost in the manufacturing and process industries. Traditional fault detection methods are able to monitor the process and detect deterioration of the equipment after their degradation and malfunction occurs. This paper presents an intelligent technique based on a neural network (NN) that monitors the health of the equipment and forecasts faults by detecting any onset of failures. In this approach, an adaptive modular NN architecture that is capable of monitoring the health of industrial machines is introduced. This technique is applied to a subsystem of a machining center. The high accuracy of the technique is verified by extensive tests, resulting in over 99% precision.     

Automated Diagnostics of Analog Systems Using Fuzzy Logic Approach

This paper presents an automated method for analog system diagnostics, which aims to detect and localize multiple faults in noisy conditions. The generic architecture of the diagnostic scheme and its stages of denoising, stamp extraction, and fault detection are explained. The method is tested on three systems of various physical nature. Then, approaches to automated diagnostics of the different classes of the systems are proposed. Machine learning methods (decision-tree-based fuzzy logic) are used to effectively detect faults. Their advantages are explained and confirmed by examples.     

Testable design of multiple-stage OTA-C filters

This paper presents a novel design and test methodology to increase the testability of multistage operational transconductance amplifier and grounded capacitor (OTA-C) filters. As assumed herein, a fault can cause the value of a passive circuit component to deviate from its normal value in order to detect such faults. This deviation causes open-circuit and/or short-circuit effects or changes the operating characteristics of the active components. That is, the catastrophic and parameter deviation faults are considered in this paper. The proposed methodology is also effective in detecting single and multiple faults. Simulation results for the faulty and fault-free circuits are compared to verify the feasibility of our design-for-testability (DFT) structure. The physical layout of a third-order Butterworth OTA-C filter is implemented by the TANNER layout tool. The extra hardware overhead to make the OTA-C filters testable is less than 9%, which is quite a reasonable value for analogue circuits