Study And Characterization Of Power Distribution Network Reconfiguration

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Study and Characterization of Power Distribution Network Reconfiguration T. Thakur and Jaswanti status of switches and the normally open tie switches, requires to satisfy the system requirement [1 8],[5 1]. From optimization point of view, the reconfiguration method have been used loss for reduction using different techniques on the other hand from service restoration point of view, the reconfiguration allows to relocate loads by using an appropriate sequence of switching operations with operating constraints taken into account. Index Terms--Combinatorial optimization, Distribution In order to deal with these problems, several evolutionautomation, Distribution systems reconfiguration (DSR). based heuristic algorithms such as Genetic Algorithm (GA), Simulation Annealing (SA) and Tabu Search (TS) have been I. INTRODUCTION used for various combinatorial optimization problems. T 1 HE electric power distribution systems consist of However, Tabu Search (TS), metaheuristic-based strategy for groups of interconnected radial circuits and have a solving combinatorial optimization problem applied in various number of constraints like radial configuration, all loads fields, has the capacity to obtain high quality solution within served, co-ordinated operation of over current protective reasonable computing time [67]. devices, and voltage drop within limits etc. Each feeder in the This paper proposes a study and characterization of distribution system has a different mixture of commercial, distribution system network reconfiguration. The effect of residential and industrial type loads, with daily load each heuristic method is observed and examined. This variations. approach provides the power distribution engineer, researcher The process of reconfiguration, by operating switches to and other with several alternatives, where qualitative, change the circuit topology of the network to reduce the application - dependent criteria can be applied following operating costs and meeting the constraints listed above is his/her experience. Our attempt is not directed at evaluating now the demand of the era for quality power supply to the and comparing relative performance of the existing algorithms consumers [1]-[3]. More-over, with increasing use of the but at presenting a clear picture of what is available so that a Supervisory Control and Data Acquisition System (SCADA) researcher in the area of power distribution network and Distribution Automation Control (DAC) equipped with reconfiguration can identify problems and seek their solutions. automated switches and remote monitoring facilities; thus, the distribution system reconfiguration has become a more viable II. PROBLEM FORMULATION IN THE GROWING DEMAND alternative for loss reduction resulting the distribution feeder OF POWER WITH CONSTRAINTS reconfiguration as a planning tool as well as a real time In order to obtain problem formulation for Distribution control tool. System Reconfiguration (DSR) problems, all the constraint Generally, power distribution network reconfiguration should be considered together. Very often, it is observed that provides services to as many customers as possible following electrical power utilities distribution system lacks in meeting fault coding and during planned outage for maintenance the quality and reliability [1], firstly due to the technological purposes with system loss minimization and load balancing of factors and secondly due to the operating factors concerning the network [4]-[5]. It allows the transfer of loads from deployment of electrical power distribution equipments and heavily loaded feeders or transformers to relatively less their loads. The other major problems are: heavily loaded feeders or transformers. Such transfers are 1. Average power transmission loss of power utilities figures effective in terms of altering the level of loads on the feeders around 5-6% of total power demand where as 60-70% of the being switched as well as in improving the voltage profile loss is estimated to be lost in distribution system. along the feeders and have affecting reduction in the overall 2. Real time information communication and co-ordination of system power losses. the protection scheme for the power distribution network The network reconfiguration problem being a complex configuration. non-linear combinational problem due to non-differential 3. Electrical power distribution system suffers unbalanced feeder structure and unbalanced loading which affects system power quality and electricity prices. T.Thakur and Jaswanti are with the Department of Electrical Engineering, Punjab Engineering College (Deemed University), Chandigarh, India-160012 4. Distribution feeder having mixture of commercial (e-mail: tilak2OO42005kyahoo.co.in; jaswanti98g yahoo.co.in) residential and industrial type loads with daily dissimilar 1-4244-0288-3/06/$20.00 (©2006 IEEE

Abstract- This paper proposes a study and characterization of distribution system network reconfiguration. This analysis of the various characteristics of the radial distribution network may help to study on a particular area of research of power distribution system. This approach provides the power distribution engineer, researcher and other with several alternatives, where qualitative, application dependent criteria can be applied following his/ her experience.

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load variations causes the peak loads at different times (non and distribution losses are as high as 20 to 30 percent of total coincidence of peaks). power generation. Distribution losses occur for the following 5. Requirement of efficient tools and techniques for multi- reasons: objective and non-differential optimization problem of * Line losses on the phase conductors. * Line losses on ground wires and ground. electrical distribution system. * Transfer core and leakages losses. * Excess losses due to lack of co-ordination of VAR III. CHARACTERIZATION OF POWER DISTRIBUTION RECONFIGURATION: VIS-A-VIS: SOLUTION elements. As reported about 30-40% of total investment is for * Excess losses due to load characteristics. distribution system in an electric power sector. Therefore, loss * Excess losses due to load impedance on the phase. So the loss estimation of distribution system is an reduction in distribution system can be efficient to reduce important task for the system operation and future planning. in transmission loss the whole power system. With this view, The of the loss estimation are composed of: purpose power utilities are especially concentrating on a loss * Conductor size design; minimization; power quality and reliability problem using * Substation expansion; network reconfiguration, as it does not require new equipment. Moreover, the network reconfiguration problem is a * Rate analysis; complex non-linear combinational problem due to non- * Loss allocation to customer; differential status of switches and the normally open tie * Energy conversion analysis; switches, determined to satisfy system requirement. From * Energy conservation promotion; optimization point of view, the reconfiguration method have * Service cost calculation; been used for loss reduction using different techniques on the * Control strategy development. Therefore, exploration about distribution losses is very other hand from service restoration point of view, the to power engineers. These losses directly effect to important reconfiguration allows to relocate loads by using an the power system losses. The distribution losses can be appropriate sequence of switching operations with operating in reduced two ways: constraints taken into account. * Installation of shunt capacitor; DSR can be seen as a combinatorial optimization problem * Network that is the selection of the proper reconfiguration for multi-objective purposes with following characteristics structure of the network for minimum losses. topological during the normal operating conditions: Power utilities are especially concentrating on a loss A. Losses reduction to reduce overall system power loss. minimization network problem using reconfiguration because B. Load balancing to relieve network overloads. In recent years, it does not new require equipment. C. Co-ordination of the protection scheme of the new considerable research has been conducted for loss configuration. D. The final network configuration is independent on the minimization. initial states of network switches. Merlin and Back [1] first time proposed the concept of E. Maximum reliability. power distribution system reconfiguration with a heuristic F. For to overcome the size of network reconfiguration. method to determine the network configuration with minimum G. Addition of automatic switches to offer flexibility in or near-minimum line losses based on a special variation of configuration. the branch-and-bound technique. D.I..H.Sun et al. [2], S. H. Don't demand continuous maintenance. Civanlar et al. [3] and M.E. Baran et al. [5] have presented I. Reduce reconfiguration cost so that it will not burden over different power flow methods for loss reduction in network planner. reconfiguration problem using branch exchange approach. J. On line reconfiguration. Dariush Shirmohammadi et al. [6] have developed a heuristic K. Minimize number of switching operation method on Merlin and Back ideas for reconfiguration network L. Easy fast solution to the problem (Algorithms). to reduce their resistive line losses. H.D. Chiang et al. [9], T.P. Therefore, network reconfiguration of distribution system Wagner [13], Koichi Nara et al. [15], S.K.Goswami et al. [16], is required for multi-objective and non-differential Robert P.Broad Water et al. [17], G.J.Peponics et al. [21] have optimization problems in the light of above considerations. also presented network reconfiguration methods for the optimization of distribution networks operation, so that IV. DETAILED ANALYSIS The detailed analysis of each characteristics of the RDN is variable loads are fed under minimum energy losses. R.J.Sarfi et al. [25] have proposed a novel method and analyzed and supported by the respective researcher in the field following the techniques applied. This approach helps Ji.Yuan Fan et al. [27] have proposed Single Loop the researcher to find a new problem in the area of interest for Optimization technique using qualitative analysis for network reconfiguration for minimum loss as an integer optimization RDN and reconfiguration. problem with a quadratic objective function. Rubin Taleski et A. Losses Reduction to Reduce Overall System Power Loss al. [29] have proposed a new method to determine the Loss minimization in power distribution system is one of configuration with minimum energy losses for a given period. the biggest challenges before power engineers. Transmission Basically, the method belongs to the methods known as

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"branch exchange technique". L.Nepomuceno et al. [30] have proposed an equivalent optimal power flow (EOPF) model of both internal and external network. Hugh Rudnick et al. [31] have reported a heuristic solution algorithm to reconfigure an electric power distribution network under normal operating conditions. A.Moussa et al. [37] have reported Genetic based algorithm to determine the states of switches for minimum loss configuration. Ying-Yi Hong et al. [41] have proposed a new method based on fuzzy C- number (FCN) and ClusterWise fuzzy regression (CWFR) analysis for developing loss formula to estimate losses in distribution system. Young Jao Eon et al. [44] have presented an improved Simulating Annealing Algorithm for network reconfiguration in large scale distribution system. Antonino Augugliaro et al. [47] have proposed a control strategy of the open-closed status of the tie switches in MV distribution network. S.F.Mekhamer et al. [48] have presented a fuzzy-heuristic method for reactive power compensation of radial distribution system. Yasuhiro Hayashi et al. [56] have proposed an algorithm to determine loss minimum configuration considering N-1 security of Dispersed Generators (DGs) for a distribution system based on Tabu Search, and strategic oscillation is introduced to search various solutions. Antonino Augugliaro et al. [62] have presented a heuristic based fuzzy sets theory for optimal operation of automated distribution network with the aims of minimizing power losses and flattering the voltage profile. Carlos A.Dortolina et al. [63] have proposed a top-down / bottom-up approach for accuracy estimating technical losses in power distribution system where a complete set of modeling data is not available. The main feature of the approach is that it can handle varying degrees of data availability. Flavio Vanderson Gomes et al. [64] have presented a new heuristic methodology using branch exchange technique. Euther Romero Ramos et al. [65] have presented a new approach based on path to node concept for power loss minimization of distribution system. Dulce Ferano et al. [67] have presented a Tabu Search (TS) based approach for reconfigure distribution networks. Ji- Pyng Chiou et al. [68] have presented variable scaling hybrid differential evolution (VSHDE). Hernan Prieto Schmidt et al. [70], Alexandre C.B. Delves, [71] and Debapriya Das [72] have proposed a methodology based on the heuristic rules and fuzzy multiobjective approach for reconfiguring distribution networks loss minimization. B. Load Balancing to Relieve Network Overloads In a distribution system, feeder reconfiguration can change the system topology under both normal and abnormal operating conditions to solve the overloading. Load imbalanced and uneven load distributions among feeder are important causes of increased system loss. Planning feeder reconfiguration by switching operations to achieve load balance among distribution feeders will reduce system losses and increase the operational flexibility by evenly distributing the capacity reserve among the main transformers. Many approaches have been proposed to solve the load-balancing problem from different prospective. Large numbers of work

have been reported in this area [4]-[5],[9]-[10],[14],[19]-[20], [22]-[23],[30],[32],[35]-[36],[43],[45],[47],[49],[51],[54],[58]. C. Co-ordination of the Protection Scheme of the New Configuration In order to ensure that the protective devices are properly coordinated in the process of new configuration, a set of rules are implemented for co-ordination, placement and selection of protective devices.. The coordination and selection rules have been developed from common practice. Some of the placement rules have been developed from common practice, where's other have been developed time-to-time future requirement basis. Robert P. Broadwater [11] has presented the computeraided protection system design algorithm. Yuan Yih Hsu et al. [18] have presented a heuristic algorithm for distribution feeder reconfiguration with protective devices. In order to ensure that the protective devices are properly co-ordinate in the process of feeder reconfiguration, the locations of the fuses for the distribution systems under study are determined by using the proposed algorithm. Takanabu Asakura, et al. [51] have proposed a methods that evaluate various item including new equipment installation cost, equipment utilization rate, reliability of the target distribution system by contingency analysis, and loss minimization. D. The Final Network Configuration is Independent on the Initial States of Network Switches Dariush Shirmohammadi, et al. [6] have developed a heuristic method based on branch-and-bound technique and Flavio Vanderson Gomes, et al. [64] have presented a new heuristic methodology based on branch exchange technique, which have the advantage that the final network configuration is independent on the initial states of network switches.

E. Maximum Reliability It has been reported that 80% of the customer service interruption are due to failures in the distribution network. In order to improve service reliability, in many countries, automation by reconfiguration are applied to the distribution network to achieve significant and immediate improvement in reliability and hence to the electricity customers. A. Makinen [8] have described a computer-aided method for the reliability analysis of a distribution system. Satish Jannavithula, et al. [24] have presented a combinatorial optimization technique based on simulated annealing. Jen-Hao Teng, et al. [43] have presented a Value based method to relocate existing feeder sectionalized that lead to a reduction in the customer interruption cost (CIC) for reliability purpose. Teng- Fa Tsao, et al. [50] have developed an reliability Assessment Model and Yiming Mao, et al. [52] have proposed a graph-based algorithm for switch placement to improve system reliability for radial distribution systems with distributed Generation. Fangxing Li [66] have presented reliability index assessment (RIA) and reliability based network reconfiguration for distribution system.

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F. For to Overcome the Size ofNetwork Reconfiguration The most common issue in distribution system deals with reforcement of an existing system for growing load demand. A good system management requires the operator to find network configurations that lead to minimum distribution cost under secure operation standards. In normal state operation, configuration management deals with controlled switches to reduce system losses and relieve network overloads. Reported paper are [26]-[27],[40],[44].

reliability purpose. Flavio Vanderson Gomes et al. [64] have presented a heuristic methodology for determine the minimum loss and minimum cost configuration of a radial distribution system.

On Line Reconfiguration The main objective is to account how load varies in distribution systems, depending on the season, on the day, and on the hour. The switching actions to reduce losses take into account the time varying nature of loads. The load profiles are G. Addition ofAutomatic Switches to Offer Flexibility in a function of customer types and they vary from one Configuration connection point to another one all over the network. The Automatic switches placed in distribution systems are online minimum loss calculation requires an accurate effectively used during emergency conditions to improve representation of the external or unobservable parts of the reliability and flexibility. New functions are needed to copy network. With reduced computational requirement and with increased power quality requirements and to fully exploit accuracy. So online reconfiguration by minimum loss the introduction of automation, power electronic devices and reconfiguration has been on demand in industrial and electric distribution generation. These new function needs addition of utility applications. Several papers have been written on this automatic switches to offer flexibility in configuration [17], subject in distribution networks [4], [5],[19],[26],[66]. [20]. K. Minimize Number ofSwitching Operation H. Don 't Demand Continuous Maintenance The minimum number of switching operations is a mixed integer nonlinear programming problem. Several papers have It is important for optimal operation that best been written on this subject in distribution networks reconfiguration distribution system doesn't demand continuous maintenance. Satish Jannavithula et al. [24] have [14],[20],[25],[38],[51],[52],[58]. All these papers present presented a new approach for optimal network routing in methodologies for the reconfiguration of distribution networks distribution planning. The main objective is to minimize the in order alleviate network overloads. The objective of these total cost which is the summation of reliability costs, feeder methodologies is either to minimize line losses with network operating limits considered as the constraints or to minimize a resistive loss, investment and maintenance costs. function of network line loading. I. Reduce Reconfiguration Cost so that It will not Burden L. Easy Fast Solution to the Problem (Algorithms) Over Planner Heuristic methods, which are used for reconfiguration In distribution system, one of the major concerns is to increase the market value of the services they provide with purpose, are fast and near to optimal solution. These are also of to understand. Numbers papers adequate quality and reliability and to lower its costs of easy operation, maintenance and construction in order to provide [29],[30],[45],[49],[56],[70] proved its validity this is reason that these are mostly used by researcher. The details of the lower rates for the customer. A. Makinen [8] has described a computer-aided method for various types of algorithm used by researchers are discussed the reliability analysis of a distribution system. The optimum below. Considerable research has been in distribution system reliability level can be reached by minimizing the total costs, including the costs of investments, losses and outages. Satish reconfiguration. Many papers have been written on this area. Jannavithula et al. [24] have presented a simulating annealing Their approach can be classified into three main categories. technique for optimal network routing in distribution 1) Classical methods combined with heuristic approach where we find branch and bound and feeder pair (loop) planning. The main objective is to minimize the total cost quadratic programming decomposition methods [1 ]-[4], which is the summation of reliability costs, feeder resistive [6],[13],[35],[40],[46],[49-50],[52]-[54],[56],[63]. loss, investment and maintenance costs. Roy Billinton et al. [25] have also presented a simulating annealing formulation 2) Heuristic based methods, where we can find paper in branch-exchange applications of these compensationfor sectionalizing device placement taking into consideration based power flow technique to Merlin and Back central outage, maintenance and investment costs. Ignacio J. Ramirej idea and more recently, heuristic methods that account for Rosado et al. [39] have presented a multi objective other practical operational constraint, like protection for optimization methodology, using evolutionary algorithms, and limited number of switching operations requirements out the best distribution network while finding reliability [5],[8],[1 1-14],[16]-[18],[22]-[23],[26],[31],[33]-[34], the costs. simultaneously minimizing system expansion [43], [45],[59]-[61],[64],[66],[70],[72]. Alberto Varges et al. [42] have proposed a reconfiguration Modern heuristic artificial intelligent based methods: 3) method, based on energy cost minimization, to MV * Genetic algorithm [7],[15],[37]-[38],[65], distribution networks. Jen-Hao Teng et al. [43] have presented * Simulating annealing [9],[24]-[25],[44], a noval method to relocate existing feeder sectionalized that * Expert systems [53],[55], lead to a reduction in the customer interruption cost (CIC) for J

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* Artificial neural networks [1O],[20],[47], * Fuzzy logic [38],[41]-[42],[48],[58],[69], * Tabu Search [32],[37],[51],[56]-[57],[62],[67], and * Evolutionary Programming [41],[53],[68],[71]. Heuristic rule produce fast and practical strategies, which reduce the computer burden associated with an exhaustive search of the solution space and can lead to a solution that is near optimal. After comparing and analyzing the above heuristic methods, it is found in [56]-[57],[67] that the computational results of the Tabu Search is better than other modern heuristic methods. V.

CONCLUSIONS

The study and characterization of distribution system network reconfiguration along with algorithms used for fast and easy operations provide the power distribution engineer several alternatives, where qualitative, application dependent criteria can be applied following his experience. The general philosophy behind the development work has been to find out efficient and flexible tool for power engineers to be used in network reconfiguration. Recently combined modem heuristic artificial intelligent based methods are used to solve multiobjective reconfiguration problem. These methodologies lead the search towards a region of potentially nondominated solutions with good characteristics, allowing the decision maker to choose the best solution that achieves a compromise among the objective functions, taking into account his or her preferences. VI. REFERENCES

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VII. BIOGRAPHIES

Dr. Tilak Thakur is born in 1963. He graduated in Electrical engineering in 1987.and MSc Engg in Power System from B.IT. Sindri and achieved his Ph.D in Electronic Instrumentation from Indian School of Mines, Dhanbad in the area of SCADA in 1999. Presently, he is Assistant Professor in the Department of Electrical

Engineering, Punjab Engineering College (PEC), Chandigarh, India.. He has a teaching

experience of more than 15 years. He is involved in active Research in Power System Automation and Control. Mrs.

Jaswanti graduated in Electrical

Engineering and post graduate from Punjab

Engineering College, Chandigarh, India. She is currently doing her Ph.D in power system.

She is also a associate member of IEI and ISTE. Her main research interests are power distribution system operation, analysis and control.