Sharif Digital Repository

This paper presents a mathematical model for simultaneous deployment of protective devices (PDs) and controlling devices (CDs) in distribution networks. The PDs include fuses and reclosers and the CDs are remote controlled switches (RCSs) and manual switches (MSs). The model is to minimize equipment costs as well as sustained and momentary interruption costs. It considers the coordination of fuses and reclosers during temporary faults involving fuse saving and fuse blowing schemes. The model is in mixed integer programming (MIP) fashion which can be effectively solved with available solvers. The performance of the proposed model is verified through applying it to Bus 4 of Roy Billinton test... 

This paper presents a mathematical model for simultaneous deployment of protective devices (PDs) and controlling devices (CDs) in distribution networks. The PDs include fuses and reclosers and the CDs are remote controlled switches (RCSs) and manual switches (MSs). The model is to minimize equipment costs as well as sustained and momentary interruption costs. It considers the coordination of fuses and reclosers during temporary faults involving fuse saving and fuse blowing schemes. The model is in mixed integer programming (MIP) fashion which can be effectively solved with available solvers. The performance of the proposed model is verified through applying it to Bus 4 of Roy Billinton test... 

This paper presents the most frequently used maintenance concerns and challenges in distribution utilities of Iran. A questionnaire is devised and distributed among the maintenance experts in more than 30 distribution utilities all over Iran and their responses have been taken under consideration in this paper. The aim is to get the most out of the successful maintenance experiences within the utilities, to find the solutions on the current common challenges on the distribution system maintenance policies, and eventually to enlighten the way on the transition to the more efficient maintenance approaches such as reliability-centered maintenance (RCM) in distribution systems  

This paper presents the most frequently used maintenance concerns and challenges in distribution utilities of Iran. A questionnaire is devised and distributed among the maintenance experts in more than 30 distribution utilities all over Iran and their responses have been taken under consideration in this paper. The aim is to get the most out of the successful maintenance experiences within the utilities, to find the solutions on the current common challenges on the distribution system maintenance policies, and eventually to enlighten the way on the transition to the more efficient maintenance approaches such as reliability-centered maintenance (RCM) in distribution systems  

In the present paper, development of the three-dimensional (3D) computational code based on Galerkin finite element method (GFEM) for solving the multigroup forward/adjoint diffusion equation in both rectangular and hexagonal geometries is reported. Linear approximation of shape functions in the GFEM with unstructured tetrahedron elements is used in the calculation. Both criticality and fixed source calculations may be performed using the developed GFEM-3D computational code. An acceptable level of accuracy at a low computational cost is the main advantage of applying the unstructured tetrahedron elements. The unstructured tetrahedron elements generated with Gambit software are used in the... 

Improving power distribution characteristics of space time block codes (STBCs), namely peak to average power ratio (PAPR), average to minimum power ratio (Ave/min), and probability of transmitting 'zero' by antenna, makes easier their practical implementation. To this end, this study proposes to multiply full diversity STBC with a non-singular matrix in multiple input multiple output (MIMO) or multiple input single output (MISO) systems with linear or maximum likelihood (ML) receivers. It is proved that the obtained code achieves full diversity and the order of detection complexity does not change. The proposed method is applied to different types of STBCs. The bit error rate (BER) and power... 

The current of outgoing feeders are very important data transmitted over SCADA system. Monitoring of these currents can help dispatching engineers to detect abnormality in energy consumption trend and minor faults in distribution network. Statistical process control (SPC) is one of the capable approaches which can be used for this purpose. Statistical process control is based on categorizing variations into assignable causes and random causes. In current paper we described the methods which were used for finding assignable causes in load trend and short time load variation in Alborz province power distribution company pilot project. Although this approach is not developed completely and some... 

In this work a microgrid is established within the geographical perspective of interest. The characteristics of the grid and its urban are employed to determine the candidate points for establishment of EV charging stations. The investment costs and operation costs are calculated for each station realizing the required constraints. This process resulted in optimum selection of EV stations. The optimization is achieved based on two different types of preliminary assumptions. In the first one, it is assumed to have only one station, while in the second one possibility of having multi-stations is considered. Using the total investment and operation costs as the objective function of... 

The communication between control centers, contact centers, field technicians and customers have been changed in previous decade and traditional analogue communication devices have been being replaced by integrated digital systems. Nowadays communication and computer network substructures are vital to distribution companies because communication system interruption can disrupt majority of services. Therefore, it is necessary to control any situation which can threat communication system. Alborz province power distribution company uses data mining methods like classification and clustering in addition to quantitative statistics for analyzing historical fault data. The result of this study is... 

Reliability of the power distribution unit (PDU) is very important in electrical systems. Since any failure in this unit leads to system failure. A commonly used method for increasing the reliability of a dc PDU is using the redundant modules. If a fault occurs in a voltage regulator of PDU, it is replaced by its redundant module. In conventional redundancy, each dc voltage regulator has its exclusive redundant modules. Therefore, if both a regulator and its redundant modules fail, the system is stopped. It is an important drawback since the exclusive redundant modules of other voltage regulators may not be used, but, the PDU cannot use them instead of faulty regulators. In this paper, the... 

In the present study, the comparison between the results obtained from the linear and quadratic approximations of the Galerkin Finite Element Method (GFEM) for neutronic reactor core calculation was reported. The sensitivity analysis of the calculated neutron multiplication factor, neutron flux and power distributions in the reactor core vs. the number of the unstructured tetrahedron elements and order of the considered shape function was performed. The cost of the performed calculation using linear and quadratic approximation was compared through the calculation of the FOM. The neutronic core calculation was performed for both rectangular and hexagonal geometries. Both the criticality and... 

Nowadays, large-scale power outages induced by ever-growing natural disasters are increasing at a galloping rate. In this regard, this paper aims at improving the resilience of power distribution systems in facing high impact low probability (HILP) events in the planning phase of the system. To this end, optimal switch placement along with the optimal distribution line hardening strategies is proposed to mitigate the repercussions of the natural calamities. So, decreasing the failure probability of the distribution lines alongside the optimal placement of remote-controlled switches (RCSs) to increase the maneuvering capability of the system, the system operator would be able to strengthen... 

In this paper, a two-stage charging management framework is proposed to exploit the potential flexibility of Electric Vehicles (EVs). The aim is to reduce drastic variations in distribution system net load caused by integration of intermittent renewable distributed generation (DG) units. In the first stage, a home-based charging method is formulated in which the desired charging schedule of EVs is obtained by minimizing the cost of energy taking into account owners' preferences. The attained charging schedules are then announced to EVs Coordinator Agent (ECA) which, as the second stage, applies an LP optimization to reduce the cost of ramp provision. Moreover, an incentive scheme is... 

Power Distribution Unit (PDU) is a power supply unit that supplies various DC voltage levels for electric equipment. Reliability of PDU is very important in electrical systems. Buck converter is frequently used in PDU to provide the lower voltage levels than the source voltage level. The output capacitor of the buck converter is the main factor of failure. In this paper, we present a method to design a buck converter with almost no inductor current ripple. If the inductor current ripple is eliminated, the output capacitor can be removed from the converter. By removing the capacitor, the reliability and transient response of the converter can be improved considerably. The proposed method is... 

In this paper, the intra-cell link adaptation problem is formulated as a constrained nonconvex nondifferentiable optimization problem to maximize the average link throughput while guaranteeing the best possible coverage reliability. We proceed to solve the resulted nonsmooth optimization problem using proximal point bundle method known in nondifferentiable optimization context. For this purpose, we first exploit the problem structure and reduce the original large scale optimization problem to a sequence of one-dimensional problems coordinated by a master program using direct primal decomposition technique. Proximal bundle method with aggregation policy is then adopted in master program to... 

Recently there has been a growing interest in using infrared light for broadband indoor wireless communications. There are two major limitations for establishing a wideband infrared communications link. The first and most important limit is the power requirements of such a link. The second important impairment is the intersymbol interference caused by multipath dispersion. In this paper we address the issue of designing an optimized transmission system to provide the best power efficiency for an infrared link. Important parameters that should be considered for this design and some examples of efficient link designs are discussed. The suggested designs can improve the power efficiency of an... 

In restructured and de-regulated power systems, generating companies (Gencos) are responsible for supplying electricity for both energy and reserve markets, which usually operate simultaneously. In this condition, the question is how much and for what price must each Genco generate for each market to maximize its profit, so this paper intends to answer to this question. In this paper, first, the combined energy and reserve markets are considered, and the Nash equilibrium points are determined. Then, the bidding strategies for each Genco at these points will be presented. The bids for the energy and 10 min spinning reserve (TMSR) markets are separated in the second stage, and again, the... 

Currently, some coarse measures like global network latency are used to compare routing protocols. These measures do not provide enough insight of traffic distribution among network nodes in presence of different fault regions. This paper presents a detailed traffic analysis of f-cube routing algorithm achieved by a especially developed tool. Per-node traffic analysis illustrates the traffic hotspots caused by fault regions and provides a great assistance in developing fault tolerant routing algorithms. Based on such detailed information, a simple yet effective improvement of f-cube is suggested. Moreover, the effect of a traffic hotspot on the traffic of neighboring nodes and global... 

This paper presents a new algorithm based on integrating the use of genetic algorithms and simulated annealing methods to optimal allocation of distributed generation resources in distribution networks. Through this algorithm a significant improvement in the optimization goal is achieved. With a numerical example the superiority of the proposed algorithm is demonstrated in comparison with the simple genetic algorithm. © 2005 IEEE