Sharif Digital Repository

Automation systems provide substantial improvement in service reliability through speeding up fault management procedure. However, this is at expense of high investments whose justification needs thorough cost/worth analyses. This paper introduces a mathematical model to optimally place automation system devices within distribution networks. The model establishes a trade-off between service reliability improvements and the relevant costs. Among different automation system devices, fault indicators and remote controlled switches are considered here. Also, the impact of manual switches is regarded since their number and location significantly affect the solution of the placement problem. The... 

The main concern of steganography (image hiding) methods is to embed a secret image into a host image in such a way that it causes minimum distortion to the host; to make it possible to extract a version of secret image from the host in such a way that the extracted version of secret image be as similar as possible to its original version (this should be possible even after usual attacks on the host image), and to provide ways of embedding secret images with larger size into a given host image. In this paper we propose a method that covers all above mentioned concerns by suggesting the idea of finding from an image data base, the most suitable host for a given secret image. In our method,... 

This study presents a novel method for fault location of transmission lines by multiple fault current measurements. In contrast to conventional methods, it is proposed to utilise several current measurements, which may be far from the faulted line. The circuit equations of the network are used to express each fault current as a function of fault location. Fault location is then estimated using a least-squares estimation technique. To achieve a robust estimation of fault location, statistical hypotheses-testing is employed for identifying erroneous measurements. The method is applicable to both synchronised and unsynchronised measurements. Moreover, fault location can be estimated regardless... 

Power system equipments are normally designed for a specific system and load situation. This situation could change significantly as a result of the system expansion or aging. Among the system equipments, circuit breakers are more sensitive to the system expansion and they must be able to isolate the faulty components if a fault occurs. As the system load increases in the future, the power network must be expanded. In this situation, either the switching equipments must be replaced in order to be able to respond to the new fault current or the fault current must be limited to the interrupting capability of the existing circuit breakers. Application of Fault current Limiters (FCL) serves as a... 

Sectionalizing switches (SSs) are often presumed to function fully reliable. However, SSs are exposed to have some malfunctions, whereby undermining their ability to improve service reliability. This study presents a model to integrate SS malfunction probability into SS placement problem. The model aims to minimize the total SSs costs as well as customers interruption cost. The proposed model is formulated in mixed integer programing (MIP), which can be easily solved via several available solvers and gain global optimal solution. The proposed model indicates the extent to which the placement problem is affected by uncertainty associated with SSs functionality, and how not considering SSs... 

Sectionalizing switches (SSs) are often presumed to function fully reliable. However, SSs are exposed to have some malfunctions, whereby undermining their ability to improve service reliability. This paper presents a model to integrate SS malfunction probability into SS placement problem. The model aims to minimize the total SSs costs as well as customers interruption cost. The proposed model is formulated in mixed integer programing, which can be easily solved via several available solvers and gain global optimal solution. The proposed model indicates the extent to which the placement problem is affected by uncertainty associated with SSs functionality, and how not considering SSs... 

Sectionalizing switches (SSs) are often presumed to function fully reliable. However, SSs are exposed to have some malfunctions, whereby undermining their ability to improve service reliability. This paper presents a model to integrate SS malfunction probability into SS placement problem. The model aims to minimize the total SSs costs as well as customers interruption cost. The proposed model is formulated in mixed integer programing, which can be easily solved via several available solvers and gain global optimal solution. The proposed model indicates the extent to which the placement problem is affected by uncertainty associated with SSs functionality, and how not considering SSs... 

In this paper we investigate the effects of superconducting shielded core reactor (SSCR) on the operation of induction generators. Large number of induction generators used in wind power plants generally increase the short circuit current level of the system. The reason is that they provide parallel reduced-impedance paths for the fault currents. Taking advantage of SSCR in wind power plants allows for using these generating units in large numbers with no concerns about the system fault current increments. The study is performed on a test system using the conventional model of an induction generator and a new effective model for SSCR based on its shielding behavior. Mathematical equations... 

A short circuit fault in an AC railway supply system could have undesired consequences; including high-amplitude current flow in the power path, the rail potential rise in the fault vicinity. This paper studies the problem of the rail voltage rise in Tehran-Karaj railway system by the use of a steady state circuit model for the AC autotransformer during a phase-to-ground fault. By using this model, all the currents and voltages of the system can be easily calculated for all possible short circuit fault locations. With the help of the derived analytical model, one can also predict the possible fault locations which may cause the protection system to operate. The estimation of the system... 

With the rapid advancement of phasor measurement units (PMUs) technology, system operators in different level of power systems have access to new and abundant measurements. Taking into account these measurements in active distribution systems (ADNs), a new algorithm for short-circuit fault detection and identification based on state estimation (SE) is introduced in this paper. In this regard, as the first step, traditional SE process is revised to be compatible with fault conditions. Then, a fault location algorithm (FLA) based on the revised SE (RDSSE) is presented which attends to detect the location of fault after diagnosing faulted zone. For this purpose, current and voltage... 

Fault indicator (FI) plays a crucial rule in enhancing service reliability in distribution systems. This device brings substantial benefits for fault management procedure by speeding up fault location procedure. This paper intends to develop a new optimization model to optimally deploy FI in distribution systems. The proposed model aims to consider a tradeoff between the total customer interruption cost and FI relevant costs, including capital investment, installation, and maintenance costs. As the main contribution of this paper, the problem is formulated in mixed integer programing, which guarantees global optimum solution achieved in an effective runtime. Moreover, the model takes... 

Smart transmission grids are intended to utilize various measurements for enhanced operation. In particular, synchronized phasor measurements have found many applications in this context. This paper presents a linear weighted least-squares (WLS) method for fault location estimation of transmission lines by synchronized voltage measurements. The measurements may be taken from the faulted line terminals or buses far from the faulted line. The circuit equations of the network are used to find the transfer function between the fault location and each voltage measurement. Next, two auxiliary variables are defined to transform the nonlinear fault location estimation problem into a linear WLS...