Sharif Digital Repository

One of the most essential part of power system are transmission lines. Transmission of power from production centers to consumption centers is duty of these lines. Any disturbance in this duty make great losses to producers and consumers. One of the most disturbance in transmission lines are short circuits that occurred because of various causes. Most faults on transmission lines occurred in stormy weather that make more troubles for fault search. So we need a tool that can find location of fault precisely and quickly. This tool named fault locator. There are many algorithms for fault location and detection on power system transmission lines. These algorithms usually are dependent on very... 

This thesis proposes a dynamic model for studding influences of suspension components behavior on rail vehicle dynamics. As the air springs are very important isolating component in rail vehicles, a new complete nonlinear air spring model, with taking into consideration of thermo–dynamical effects, is developed. The model coefficients are tuned based on the real test data and it can be easily used in dynamic modeling of air springs. The new proposed vehicle model is a complete track–vehicle model with 70 degree of freedoms which is addressed as a modular type. Experimental results from complete rail–vehicle field test, showed remarkable agreement between proposed model and test results.... 

Distributed embedded systems are widely used in safety-critical applications, such as avionics platform and flight control system. Faults in such applications may cause catastrophic effect. Therefore, these systems must be fault-tolerant and must be designed not only to detect faults but also to recover from faults. Fault tolerance is normally realized on multi-processor system via temporal duplication (time-redundancy) or spatial duplication (hardware-redundancy) depending on the availability of the slack time. Slack time is defined as the difference between the deadline and execution time. Duplication is a common technique to achieve fault tolerance in safety-critical applications, but may... 

Fast and accurate fault diagnosis has a significant role in the power system operation. For a power system to come back to the normal state, the precise fault diagnosis is necessary. The current practice in power system fault diagnosis needs operators in the control center to use data of PR and CB in order to infer the faulted section based on their experiences. Expert systems and artificial intelligence have been suggested as alternatives to the human expert experience and inference. Other model- and optimization-based methods have also been reported for fault diagnosis, provided that similar data is available from the SCADA system.Nevertheless, in large disturbances resulting in partial or... 

A power transmission system includes transmission lines that are interconnected for economic and security reasons. Power systems are often prone to faults at the transmission level, since transmission lines are spread over vast geographical areas. Being the most serious events in power systems, blackouts are often initiated by a fault and a sequence of events afterward leads to partial or complete power outage. In this condition, fault diagnosis is the first step for power system restoration. In this research work, a new approach utilizing impedance-based fault location is introduced for fault diagnosis. By developing wide-area measurements in the context of smart grids, accurate... 

The goal of this master thesis is to develop a new accurate numerical algorithm for digital differential relay to protect a power transformer. This work employs specially developed software to simplify its input signal processing task which helps to quickly and accurately detect and clear the transformer internal faults. The available commercial transformer digital differential relays lack the required sensitivity to detect turn to turn faults when a few numbers of turns (less than 10% of the winding) are involved. This work presents a new equivalent circuit for transformer when a turn to turn fault occurs on either winding. This equivalent circuit helped to develop an accurate algorithm for... 

In continous chemical process, disturbances usually propagate along the process. This project describes a data-driven method for identifying the direction of propagation of disturbances using historical process data. The concept is the application of Transfer Entropy, a method based on the conditional probability density functions that measures directionality of variation. For demonstration purposes the transfer entropy method is used to isolate the root-cause of the disturbance in the Tennassee Eastman benchmark process  

Lifetime extension would be a necessary preventive action to halt micro cracks expansion on the airplane external surface. To decide about whether to perform this operation, one should examine technological maturity, costs and technical parameters. Technical status in lifetime extension is one of the major drivers of this decision which should be considered in the first step of technology management process which is known as the technology attractiveness step. In this research, major technologies of rejuvenation is examined and categorized by the technology mapping. Also, key processes of rejuvenation and technological fields ranking has been determined by the procedural view tools of the... 

The present thesis is concerned with design and development of automated irrigation system pilot. This system is obtained by equipping each regulating gate of irrigation network with a controlling hardware. This hardware is designed and developed in this project for Iran’s regulating gate, which are either slide gate or radial gate. This hardware consists of a) Ultrasonic sensor for measure gate upstream water level, b) Wireless modem for exchanging measurements between automated gates, c) controller, d) Electric motor and driver, e) shaft encoder and f) adaptor. The satisfactory performance of this hardware is shown via several experiments on the pilot  

Wireless Body Area Network (WBAN) is a set of various physiological sensors for remote monitoring and controlling of the patient’s health status. Detection of anomalies, containing faults and physiological stresses, and distinguishing between them can eliminate the need for constant presence of specialists and decrease the occurrence of False Alarm Rate (FAR).A supervisory hardware platform for WBAN architecture is introduced and implemented in this thesis. The proposed architecture contains three sensors for recording of biomedical signals, heart rate, SpO2 and body temperature simultaneously and transmitting them to central node wirelessly through Wi-Fi standard. This proposed architecture... 

In this thesis the problem of optimal robust fault detection has been studied. Optimal Fault Detection Filter (FDF) design, by using a Linear Matrix Inequality (LMI) structure for both linear systems with polytopic uncertainties and nonlinear Lipschitz systems has been considered. In this regard, a novel LMI is introduced which is capable of calculating the maximum lower bound of H− index with great accuracy.Then, based on the parameter-dependent Lyapunov function and the property of having convexity in combination of certain state space equations, the result is extended to polytopic uncertain systems. Afterward the design of an optimal observer-based residual generator, in the sense of... 

Lean Management is a set of modern procedures that uplifted Japanese manufacturers' status in global markets. The core principle of lean management is to eliminate every process or operation which creates no value, directly and indirectly. To this day, lean has been more focused on production. But eliminating the wastes in service organizations in crucial, due to nature of service. In this thesis, first the lean concept and the Middle East bank is discussed and a literature review on lean studies is presented. Then a vision for the future is envisioned and a questionnaire for conducting a Corporate Diagnosis is developed. In the next step, a lean management system for the bank is implemented... 

Fault-tolerant ability is more subjected in Cascaded H-Bridge Multilevel Inverter due to its high-power medium-voltage applications and large number of semiconductors switches used in its structure. In this thesis, the goal is performance improvement of Cascaded H-bridge Multilevel Inverter under faulty conditions. Since to achieve the post-fault ability two steps; fault detection and post-fault control are required, both steps are considered in the improving process. In this dissertation, first operation of Cascaded H-Bridge Multilevel Inverter in normal and faulty condition is surveyed. Then, the conventional fault detection methods are mentioned and post-fault control methods are... 

Rolling element bearings (REBs) are one of the most critical components in rotating ma-chines. Failure of these components may lead to fatal and costly breakdowns in rotating machinery. Therefore, it is significant to detect faults at early stage accurately. The pur-pose of this study is to compare vibration analysis and shock pulse method (SPM) in early detection of fault and remaining useful life prediction of REBs. To the aim, a set of ac-celerated life tests on REBs was planned. Vibration and shock pulse values accelerated life tests of the REBs were simultaneously measured from the moment of start to the end of the failure by two vibration and shock pulse sensors and their changes were... 

AC/DC/AC converters are widely being used in a variety of power applications. Continuity of service of these systems, as well as their reliability and performance are now of the major concerns. Indeed, the failure of the converter can lead to the total or partial loss of the control of the phase currents and can cause serious system malfunction or even shutdown. Thus, uncompensated faults can quickly endanger the system. Therefore, to prevent the spread of the fault to the other system components and to ensure continuity of service, fault tolerant converter topologies associated with quick and effective fault detection and compensation methods must be implemented. In this thesis, the... 

Fault detection and identification is one of the major issues and challenges in the field of engineering and currently is considered as an active field of research. As the replacement of human in dangerous or inaccessible environments, robotic mechanical systems can be used which exposes to a variety of stresses and actions that causes faults in the actuators or sensors. Accordingly, detection of fault at the earliest possible time after the fault accurence and its identification such that real flaw waveform is being extracted, can prevent more damage to the system without any need to human immediate interference. Model based approach in recent decades has shown their ability to detection... 

Five-Level Active-Neutral-Point -Clamped (5L-ANPC) converter is used for medium-voltage and high-power applications. In many of these applications, availability and robustness against fault are the most important issues. On the other hand, this converter is made of a large number of power semiconductor switches, diodes and capacitors which could increase the failure probability. Thus, fault detection of power circuit elements is necessary for fault tolerant operation of the converter. In this thesis, following an introduction to the topology and operation principles of Five-Level Active Neutral point clamped converter, a novel open-circuit fault detection and localization method is... 

Short-circuit fault detection is mandatory in a high voltage DC power supply to prevent fatal damage. The majority of converters employ a single sensor to detect the short-circuit fault. This attribute increases the interference vulnerability of the fault detection system in the presence of noise. Therefore, miss detections and false alarms are possible to occur. Miss detections and false alarms are harmful catastrophes in most applications. A commonly used method to suppress the noise impacts is using a low-bandwidth low-pass filter. However, the use of the low-bandwidth low-pass filter reduces the speed of fault detection due to the filter delay. This paper proposes a fast fault detection... 

Nowadays by increasing the number of processing cores in system-on-chip, using networks-on-chip, as an optimized interconnection foundation for transferring data between processing cores is inevitable .Based on this, the necessity of designing and implementing an optimized structure for testing network-on-chip, considering various overheads such as power consumption, latency, bandwidth and area, becomes an important issue in designing network-on-chip. The purpose of this project is to design an optimized structure for testing routers and connecting links in network, which considers power consumption overhead, latency and area overhead on one hand, and fault coverage on the other hand.... 

Fatigue crack growth can have harmful effects on the reliability rotary machine. While an early warning to crack, can be used to extend the life of these expensive machines and increase reliability.Structural Vibration Condition Monitoring as a primary fault detection method, achieved to a lot amazing result and for this reason studies vibration behavior of cracked rotational shaft is a big issue for engineers of dynamic machine.In this research, first check the fault detection methods based on structural vibration condition monitoring, mode shape methods were extracted. Then by modeling rotational shaft in computer and creation of crack on it, fault detection quality of these methods have...