Mohammad Tavakkoli Bina; Mehdi Sirjani; Danyal Ahmadi
Abstract
Upgrading the voltage level of a transmission line is named as one solution to increase the transmitted power. This paper introduces the results of a research project in which the upgrade of Saravan-Sooran double circuit transmission system from 63 kV to 230 kV is studied. In this context, the towers ...
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Upgrading the voltage level of a transmission line is named as one solution to increase the transmitted power. This paper introduces the results of a research project in which the upgrade of Saravan-Sooran double circuit transmission system from 63 kV to 230 kV is studied. In this context, the towers remain in their current locations, where the new structure of towers and insulators as well as the conductors are presented using the weather condition in Sistan-Baloochestan province. Four designs are presented as alternatives of the available design, considering the economical analysis of the transmission system. The finalized chosen design satisfies significant savings for the system, while providing both right-of-way and required standards.
Arash Tavighi; Saeed Afsharnia; Hassan Monsef
Abstract
Today, with attention to increase in sensitive electrical equipments application in distribution networks and their susceptibility to the power quality deficiencies, the protection necessity of sensitive loads against undesirable effects of these disturbances are in focus. So, in this paper voltage sag ...
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Today, with attention to increase in sensitive electrical equipments application in distribution networks and their susceptibility to the power quality deficiencies, the protection necessity of sensitive loads against undesirable effects of these disturbances are in focus. So, in this paper voltage sag deficiency and Dynamic Voltage Restorer (DVR) would be introduced as the most prevalent power quality problems and most effective voltage sag’s compensators, respectively. Continuously, different parts of DVR structure would be discussed in which control system would be taken into account as the most important part. In this part, after different compensation strategies analysis and with attention to great importance of compensator response in sensitive load protection against the duration of voltage sag, various voltage estimation algorithms would be introduced. Afterwards a novel estimation algorithm would be proposed which has the desirable accuracy and less delay among the mentioned ones. Then a proposed control system based on the proposed algorithm in the fault detection system and pre-fault based symmetrical component strategy would be introduced. Finally the effects of the novel system on asymmetrical voltage sag and swell of the distribution system improvement would be simulated in Matlab/Simulink.
Amir Pirouz Ghale; Majid Sanaye Pasand; Hamed Asadi
Abstract
Power system blackouts have become a serious problem for electric utilities especially in recent years. Different forms of system instability have emerged in recent blackouts, such as voltage instability and frequency instability. To counteract each form of system instability, special algorithms have ...
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Power system blackouts have become a serious problem for electric utilities especially in recent years. Different forms of system instability have emerged in recent blackouts, such as voltage instability and frequency instability. To counteract each form of system instability, special algorithms have been designed in the protection system, e.g. Under Frequency Load Shedding (UFLS) and Under Voltage Load Shedding (UVLS) schemes. One of the major weaknesses of these algorithms is that combination of different forms of instability is not considered in their design, while any one form of instability may not occur in its pure form. This is particularly true in highly stressed systems and for cascading events. This paper presents an adaptive algorithm to combine UVLS and UFLS schemes. The purpose of this method is to enhance the flexibility of under frequency relays and increase the security of power system during large disturbances by improving system voltage stability margins. In the proposed algorithm, loads with greater voltage decay are shed sooner. In this way, locations of load shedding become dependent to the location of disturbance and voltage stability margins of the system are enhanced. Indeed, load shedding is performed faster for severe events accompanying large voltage or frequency declines. Using this load shedding method, faster reactions could be obtained for major system failures. This way, system blackouts could be better controlled. Performance of the proposed method is compared with the conventional UFLS method. In this paper, dynamic model of the Khorasan HV network of Iran national grid is used for simulation. This network includes 75 high voltage 400 kV and 132 kV buses with about 2700 MW of generation. Performance of the schemes has been evaluated using dynamic simulations as well as the P-V curves, and reactive power margins for a number of events. Simulation results show that conventional UFLS algorithm will not necessarily result in acceptable voltage stability margins for the system following a disturbance. Meanwhile, the proposed algorithm improves voltage stability margins. The proposed algorithm is suitable for saving system stability after occurrence of major system disturbances.
Ahmad Saghafi; Seyyed Mehdi Fakhraee; Manoochehr Manteghi
Abstract
Ultra-wideband (UWB) radio is a promising technology for low-cost, high-rate communications at short ranges. However, high bandwidth and low power of the UWB signals impose some difficult challenges in signal processing and implementation of the receiver. Acquisition of the signal timing is the first ...
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Ultra-wideband (UWB) radio is a promising technology for low-cost, high-rate communications at short ranges. However, high bandwidth and low power of the UWB signals impose some difficult challenges in signal processing and implementation of the receiver. Acquisition of the signal timing is the first task to be performed in a coherent receiver. The high bandwidth of UWB signals demand for fine time resolution search of the uncertainty region. Thus, for an accurate acquisition, the uncertainty region must be searched in small step sizes, imposing a large search space. Moreover, the low transmission power of UWB systems requires the receiver to observe the received signal for a long time in order to make a reliable decision. These are the two reasons that cause the receiver to spend a long time for acquisition of the signal timing. The fine time resolution, on the other hand, results in a large number of resolvable multipath components which locking to many of them might be treated as a good estimate of the timing information of the received signal. Hence, in a multipath channel there may be more than one phase that could be considered a reliable estimate of the true signal timing.
In this paper, we propose a new two-stage search space reduction technique which speeds up the acquisition process without adding additional complexity to the conventional serial acquisition method. Specifically, we divide the search space into some groups of consecutive phases and the first stage tries to find a set of possible positions of the true phase relative to the positions of the groups using a special template signal. When a set of phases?one from each group?is declared to include the true phase, the second stage tries to find the absolute position of the true phase by searching the relative positions in each group using a simple template signal. The performance of the proposed method is analytically evaluated in terms of mean acquisition time and the results are validated through computer simulations. For the simulations we performed in this paper, a complete fully parameterized model of the system is designed using MATLAB/Simulink software. The results show a significant improvement in acquisition time with no additional complexity.
Javad Rasti; Seyyed Amir Monajjemi; Abbas Vafaei
Abstract
Reducing the number of colors in an image while preserving its quality, is of importance in many applications such as image analysis and compression. It also decreases memory and transmission bandwidth requirements. Moreover, classification of image colors is applicable in image segmentation and object ...
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Reducing the number of colors in an image while preserving its quality, is of importance in many applications such as image analysis and compression. It also decreases memory and transmission bandwidth requirements. Moreover, classification of image colors is applicable in image segmentation and object detection and separation, as well as producing pseudo-color images. In this paper, the Kohenen Self-Organizing Map Neural Network is employed to form an adaptive color reduction method. To enhance the performance of this method, we have used redundant features obtained by one-to-one functions from three main components of the color image (e.g. Red, Green and Blue channels). Exploiting these features will increase the color discrimination and details illustration ability of the network compared to the conventional approaches. This method leads to satisfactory results in image segmentation and especially in small object detection problems. It is also investigated that if the number of features in Kohenen network grows even by using non-deterministic one-to-one functions, the network revenue considerably improves. Moreover, we will study the effect of various adaptation algorithms in Kohenen network training stage. Again using a multi-stage color reduction procedure which employs both Kohenen neural networks and conventional vector quantization schemes improves the performance. Several experimental results are represented to simplify the comparison of different approaches.
Parna Shabestari; Mohammad Hossein Kahaei
Abstract
Determination of mobile localization with time of arrival (TOA) signal is a requirement in cellular mobile communication. In some of the previous methods, localization with non-line-of-sight (NLOS) paths can lead to large position error. Also for simplicity, in most simulations suppose non stationary ...
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Determination of mobile localization with time of arrival (TOA) signal is a requirement in cellular mobile communication. In some of the previous methods, localization with non-line-of-sight (NLOS) paths can lead to large position error. Also for simplicity, in most simulations suppose non stationary actual environments as stationary. This paper proposes (residual test + recursive least square) ((RT+RLS)) that has a good application in non stationary environments. In this algorithm, residual test (RT) that can simultaneously determine the number of line- of-sight (LOS) base stations (BSs) and identify them. In simulation studies, the RT can determine the correct number of LOS-BS over 90% of the time. Then using TOA signals obtain these BSs as input of RLS algorithms and estimate mobile position in high attention and low calculation.
Karim Abbaszadeh; Mohammad Ardebili; Esmaeel Sarani
Abstract
Induction Motor especially the squirrel cage type of this motor plays important role in industry. According to the application type, this motor place against various stresses that are caused failure in the motor. The most common failure is related to the Stator winding. Among these failures are turn-to-turn, ...
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Induction Motor especially the squirrel cage type of this motor plays important role in industry. According to the application type, this motor place against various stresses that are caused failure in the motor. The most common failure is related to the Stator winding. Among these failures are turn-to-turn, coil-to-coil and phase to phase faults. Flow the high current do to the induction results in phase-to-phase failures cause the very high heat production and ultimately lead to phase to body faults. In order to extract diagnosis patterns to identify the healthy machine from Faulty machine, it needs to exact modeling of that failure type. Among of the modeling methods, the methods based on the analysis of magnetic field and geometric situation and consider the construction machines, have a high accuracy. Magnetic equivalent circuit methods in addition to the above features have the ability to model spatiotemporal Harmonics. For this reason, this method gets the more accurate modeling results inspect to other methods. In this paper, first presents a 3 hp machine modeling using magnetic equivalent circuit in different working conditions including healthy, the turn-to-turn, coil-to-coil and phase to phase, Then the models are simulated. Comparison with results obtained from the proposed models and experimental results verified and approved the accuracy of proposed methods.
Faramarz Faghihi; Hossein Heydari; Vahid Abbasi
Abstract
The higher frequency transient signals generated as a result of a power system fault or disturbance provide the basis for an alternative approach to power system containing connectors and cables result in unsuitable operation of the system. However one major challenge is the need to ensure that the transients ...
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The higher frequency transient signals generated as a result of a power system fault or disturbance provide the basis for an alternative approach to power system containing connectors and cables result in unsuitable operation of the system. However one major challenge is the need to ensure that the transients to be neutralized by electromagnetic compatibility (EMC) issues and cabling routes.
This paper proposes novel method for optimal cable routings and connectors; a combinatorial design Algorithm, to choose the best path when two or more physical paths are available. The best path from EMC point of view can be chosen based upon various criteria such as monetary cost minimization, voltage drop and quality (electromagnetic compatibility) parameters. This paper initially provides a numerical 2D and 3D resolution of the problems of radiation generated by current sources. The approach is based on the finite element method (FEM) associated with absorbing boundary conditions. The presented model makes it possible to consider wave propagation and their effects in heterogeneous mediums in transient which can be applied in EMC for the simulation of radiation. First, the formulations of the electromagnetic problem are detailed. The simulation results are used for the cabling routes with respect to undesirable field distribution in the specified regions. Finally by the use of Multi Criteria Decision Making (MCDM) optimal routes for cabling based upon the above mentioned criteria are chosen. The proposed method is successfully implemented on 25kA current injection transformer system".
