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Now showing items 1 - 16 of 69

  • Reliability Assessment of Protective Relays in Harmonic-Polluted Power Systems

    Jedrzejczak, J.   Anders, G. J.   Fotuhi-Firuzabad, M.   Farzin, H.   Aminifar, F.  

    Proliferation of distributed generations (DGs) and power-electronics-based loads is bringing about more harmonic-polluted power signals. While some failures may occur as a consequence of nonsinusoidal current or voltage waveforms, existing reliability models of protection relays have not taken the harmonic-related failures into consideration. This paper develops a comprehensive Markov reliability model to categorize the possible functional states of a component, say a transmission line, protected by a relay, operating in a harmonic-polluted environment. In order to make the proposed model practically tractable, it is further simplified in two ways, through merging the states of the same consequence. The first simplified model focuses on the power component reliability assessment; while the other is built for reliability analysis of a protection system. Calculation of transition rates and how the resultant model is mathematically evaluated are then discussed. Numerical analyses and outcomes are based on the real-world data taken from Canadian substations. Accordingly, the results and conclusions drawn in this paper would be interesting to both academia and industry. Moreover, the proposed reliability assessment methodology is readily applicable in scrutinizing the impacts of harmonic pollution on the protection devices of other power components.
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  • Impacts of Fault Diagnosis Schemes on Distribution System Reliability

    Kazemi, S.   Lehtonen, M.   Fotuhi-Firuzabad, M.  

    Design and development of fault diagnosis schemes (FDS) for electric power distribution systems are major steps in realizing the self-healing function of a smart distribution grid. The application of the FDS in the electric power distribution systems is mainly aimed at precise detecting and locating of the deteriorated components, thereby enhancing the quality and reliability of the electric power delivered to the customers. The impacts of two types of the FDS on distribution system reliability are compared and presented in this paper. The first type is a representative of the FDS which diagnoses the deteriorated components after their failing. However, the second type is a representative of the FDS which can diagnose the failing components prior to a complete breakdown and while still in the incipient failure condition. To provide quantitative measures of the reliability impacts of these FDS, the comparative and sensitivity case studies are conducted on a typical Finnish urban distribution network.
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  • Fuzzy Dynamic Thermal Rating of Transmission Lines

    Shaker, H.   Fotuhi-Firuzabad, M.   Aminifar, F.  

    Dynamic thermal rating (DTR) of transmission system facilities is a way to maximally realize the equipment capacities while not threatening their health. With regards to transmission lines, the allowable current of conductors is forecasted based on the environmental situations expected in some forthcoming time periods. Due to the fact that weather conditions continuously vary, sampling points are very limited against many line spans, and the measurements have an inherent error, uncertainties must be appropriately included in the DTR determination. This paper adopts the fuzzy theory as a strong and simple tool to model uncertainties in the DTR calculation. Since DTR intends to determine the line capacity for some periods ahead, the capability of fuzzy computation in predicting future phenomena is very fruitful here. In the proposed model, variables, such as ambient temperature, wind speed, wind direction, and solar hour angle are assumed to be fuzzy numbers. Numerical simulations are provided based on inputs taken from real databases and reasonable assumptions as well. The results obtained support the validation and efficiency of the proposed model.
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  • Guest Editorial Special Section on Microgrids

    Fotuhi-Firuzabad, M.   Iravani, R.   Aminifar, F.   Hatziargyriou, N.   Lehtonen, M.  

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  • Reliability Study of HV Substations Equipped With the Fault Current Limiter

    Fotuhi-Firuzabad, M.   Aminifar, F.   Rahmati, I.  

    Of particular interest to restrict the short-circuit level of interconnected power systems is to exploit fault current limiter (FCL) technologies. FCLs let the system planners devise new reliable and rather economical substation configurations and provide the possibility of proposing a promising cost-effective and prompt solution to the fault current over duty problem in the existing substations. This paper attempts to assess reliability of substation architectures accommodating the FCL operation and, besides, numerically investigates the FCL's impacts on the substation reliability indices. In order to clarify the proposed approach, two case studies with and without FCL are analyzed and compared. Although the discussions raised here are applicable for reliability modeling of all structures, five common substation configurations, namely: (1) single-bus single-breaker; (2) double-bus single-breaker; (3) ring bus; (4) one breaker and a half; and (5) double-bus double-breaker are considered in this paper. Numerical studies reveal that FCL deployment, while keeping the maximal flexibility of substation, may deteriorate the reliability indices of the substation due to the possible failures of FCLs.
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  • ATC enhancement using TCSC via artificial intelligent techniques

    Rashidinejad, M.   Farahmand, H.   Fotuhi-Firuzabad, M.   Gharaveisi, A. A.  

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  • Distribution system, reliability enhancement using optimal capacitor placement

    Etemadi, A. H.   Fotuhi-Firuzabad, M.  

    Failure statistics of most utilities indicate that distribution systems make the greatest individual contribution to the unavailability of supply to customers. Optimal capacitor placement in distribution systems has a number of advantages such as reducing losses, improving voltage profile, improving power factor and so on. The conventional objective function of the optimal capacitor placement consists of the total cost of losses and investments. Since capacitors supply reactive loads locally, they improve the load-carrying capability of the lines and therefore play the same role as redundant lines. Thus, optimal capacitor placement can also improve the reliability indices of a distribution system. Therefore two new objective functions are defined here. The first one is defined as the sum of reliability cost and investment cost. The second is defined by adding the reliability cost, cost of losses and investment cost. The latter is a comprehensive objective function which is the resultant of the conventional and reliability-based objective functions. This problem is solved using a particle swarm optimisation-based algorithm. The effectiveness and applicability of the proposed approach are examined using a distribution network.
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  • Bidding strategy in pay-as-bid markets based on supplier-market interaction analysis

    Bigdeli, N.   Afshar, K.   Fotuhi-Firuzabad, M.  

    In this paper, a new bidding strategy for pay-as-bid market suppliers is introduced. This method is based on a systematic analysis of interactions of market with the suppliers via several market indices as well as forecasting important indices by artificial neural networks. Besides, the proposed method considers the practical limitations in the system and deals with incomplete information handling, closely. Next, a strategic bidding approach is proposed for optimal bidding by the suppliers. In these investigations, the paper focus is on the experimental situation of Iran electricity market as a pay-as-bid market and a sample generating company with several generating units from this market is considered as the benchmark. The results of applying this approach to this generating company are representative of good performance of the proposed method. (C) 2010 Elsevier Ltd. All rights reserved.
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  • Reliability assessment of an automated distribution system

    Kazemi, S.   Fotuhi-Firuzabad, M.   Billinton, R.  

    Automation can greatly enhance distribution-network reliability by speeding up service restoration and thus significantly reduce customer-outage time. The paper presents an approach to assess quantitatively the adequacy of a particular automated distribution scheme designated as the `low interruption system' (LIS). Owing to the use of a high-speed communication system and line sensors, this automated scheme can reduce drastically the number of interruptions, the service interruption time and also the area affected by the fault. This scheme provides a simple and cost-effective way to automate distribution systems in which the remotely controlled switches speed up isolation of faulted sections and the restoration of healthy sections through alternative routes. The step-by-step calculation procedure is presented using a typical small automated distribution system. The proposed technique is then applied to a larger distribution system to examine the effectiveness of the technique and also to examine the level of reliability improvement achieved by automation
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  • Modeling of unified power quality conditioner (UPQC) in distribution systems load flow

    Hosseini, M.   Shayanfar, H. A.   Fotuhi-Firuzabad, M.  

    This paper presents modeling of unified power quality conditioner (UPQC) in load flow calculations for steady-state voltage compensation. An accurate model for this device is derived to use in load flow calculations. The rating of this device as well as direction of reactive power injection required to compensate voltage to the desired value (1 p.u.) is derived and discussed analytically and mathematically using phasor diagram method. Since performance of the compensator varies when it reaches to its maximum capacity. modeling of UPQC in its maximum rating of reactive power injection is derived. The validity of the proposed model is examined using two standard distribution systems consisting of 33 and 69 nodes, respectively. The best location of UPQC for under voltage problem mitigation in the distribution network is determined. The results show the validity of the proposed model for UPQC in large distribution systems. (C) 2009 Elsevier Ltd. All rights reserved.
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  • Reliability evaluation of transmission network including effect of protection systems

    Alesaadi, A. -R.   Haghifam, M. -R.   Fotuhi-Firuzabad, M.  

    Transmission network reliability evaluation considering effects of protective systems is investigated in this paper. Protective system faults are one of the main Sources of cascading outages and may lead to vast blackouts. Desired performance of the protection system has a significant role in the improvement of network reliability. The proposed method is based on minimal cutset approach. In the proposed method, all elements of the transmission and subtransmission substations can be considered in which subtransmission substations are taken as output nodes. A sensitivity analysis of network reliability to component reliability parameters is performed. Finally the effectiveness of the method was tested in a real network with satisfactory results. Copyright (C) 2007 John Wiley & Sons, Ltd.
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  • A method for reserve clearing in disaggregated model considering lost opportunity cost

    Afshar, K.   Ehsan, M.   Fotuhi-Firuzabad, M.   Amjady, N.  

    In this paper, a new formulation for clearing reserve market in a deregulated environment with separated energy and reserve market is introduced. In the proposed method, reserve market is cleared such that the costs associated with capacity reservation, producing energy in real-time, opportunity cost of those units which are accepted in the energy market and backed down from the accepted values to participate in the reserve market are minimized. This optimization problem is formulated and solved using linear programming method. Finally, the proposed method is applied to a six units test system to examine the applicability and effectiveness of the proposed method. (C) 2007 Elsevier B.V. All rights reserved.
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  • Composite system reliability assessment incorporating an interline power-flow controller

    Moghadasi, S.-M.   Kazemi, A.   Fotuhi-Firuzabad, M.   Edris, A.-A.  

    The impact of an interline power-flow controller (IPFC) on composite system delivery point and overall system reliability indices is examined in this paper. In this application, the IPFC with dc transmission lines is employed in a system for coordinated control of line impedances of two, distance away, transmission lines with the objective of managing power flows on the two lines. It is also used to balance the real power being transferred between the compensated lines. For this purpose, the reliability model associated with a converter station has been developed and incorporated in an IPFC reliability model. A number of reliability indices are calculated at both the loadpoint and system levels to illustrate the impact of employing IPFC and examine the effects of different failure modes on the system performance. The technique is applied to the IEEE reliability test system and the results are presented. The results indicate that IPFC improves system reliability.
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  • Cost-benefit analysis and MILP for optimal reserve capacity determination in power system

    Afshar, K.   Ehsan, M.   Fotuhi-Firuzabad, M.   Amjady, N.  

    In this paper, an approach for optimal determining reserve capacity in the electricity market is presented. This paper describes a method for setting the optimum value of reserve capacity based on the cost of its provision and the benefit derived from its availability. Reduction of customer outage cost is interpreted as the benefit of reserve capacity. In the proposed method, reserve is procured up to the point where the marginal cost of procuring reserve is equal to the marginal value of this reserve capacity. The proposed method can be formulated as a mixed-integer linear program (MILP) and solved with large-scale commercial solvers. The proposed method is applied to the IEEE reliability test system (IEEE-RTS) in order to examine the effectiveness of the proposed method. (C) 2007 Elsevier Inc. All rights reserved.
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  • A novel approach to determine minimal tie-sets of complex network

    Fotuhi-Firuzabad, M.   Billinton, R.   Munian, T.S.   Vinayagam, B.  

    Network reliability analysis is usually based on minimal path or cut enumeration from which the associated reliability expressions are deduced. The cut-set method is a popular approach in the reliability analysis of many systems from simple to complex configurations. The computational requirements necessary to determine the minimal cut-sets of a network depend mainly on the number of minimal paths between the source and the sink. A technique designated as the "Path Tracing Algorithm" is presented in this paper, which can handle both simple and complex networks, and considers both unidirectional and bi-directional branches. A step by step procedure is explained using a bridge-network. The algorithm is easy to program, and does not require limits on the size of the network. The applicability of the proposed technique is illustrated by application to a more complicated system
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  • Adequacy Assessment of Small Isolated Power Systems Using a Well-Being Approach

    Fotuhi-Firuzabad, M.   Rashidinejad, M.   Billinton, R.  

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