IMPLEMENTATION OF NETWORK RECONFIGURATION TECHNIQUE FOR LOSS MINIMIZATION ON A 11KV DISTRIBUTION SYSTEM OF MRS SHIMOGA-A CASE STUDY

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1 IMPLEMENTATION OF NETWORK RECONFIGURATION TECHNIQUE FOR LOSS MINIMIZATION ON A 11KV DISTRIBUTION SYSTEM OF MRS SHIMOGA-A CASE STUDY PROJECT REFERENCE NO. : 37S0848 COLLEGE : PES INSTITUTE OF TECHNOLOGY AND MANAGEMENT, SHIVAMOGGA BRANCH : ELECTRICAL AND ELECTRONICS ENGINEERING GUIDE : SHIVAKUMAR L.N STUDENTS : ABDUL KAREEM S.J AKSHATHA D.S BHUVANESHWARI.S SEETHARAMA Keywords: Distribution system, Reconfiguration, Switching indices, weighing factor Introduction: The demand for electricity is continuously increasing while the generation of electricity is limited by many constraints. Therefore both utility and the consumer have to mutually interact to utilize optimally the available electrical energy for the mutual benefits. Because of the rapid industrial growth, there is a considerable rise in demand for electrical energy from various categories of consumers. In the current scenario, we are facing a difficult task of matching the availability with the ever increasing demand. Nowadays because of increasing demand for electrical energy two problems exists. 1) Maintaining the uniform distribution of loads. 2) Reducing the losses in the power system to improve the end-use electrical demand. The different types of distribution system configuration are: 1) Radial configuration. 2) Loop configuration. 1

2 The Radial distribution system is the cheapest to build, and is widely used in sparsely populated areas. A radial system has only one power source for a group of customers. A power failure, short-circuit, or a downed power line would interrupt power in the entire line which must be fixed before power can be restored. A loop system, as the name implies, loops through the service area and returns to the original point. The loop is usually tied into an alternate power source. By placing switches in strategic locations, the utility can supply power to the customer from either direction. If one source of power fails, switches are thrown (automatically or manually), and power can be fed to customers from the other source. The loop system provides better continuity of service than the radial system, with only short interruptions for switching. In the event of power failures due to faults on the line, the utility has only to find the fault and switch around it to restore service. The fault itself can then be repaired with a minimum of customer interruptions. The loop system is more expensive than the radial because more switches and conductors are required, but the resultant improved system reliability is often worth the price. Even though loop configuration has better advantages, we go for radial configuration because, 1. Simplest as fed at only end. 2. The initial cost is low. 3. Useful when the generating is at low voltage. 4. Preferred when the station is located at the centre of the load. The performance of distribution system becomes inefficient due to the reduction in voltage magnitude and increase in distribution losses. Since the distribution power system is the final stage of the distribution process from the source to the individual customer, it has seemed to contribute the greatest amount of power loss in which finally resulted the instability in the system. Thus, many researchers have been focusing on power loss minimization in the distribution system by using various methods. Among the various methods of loss minimization, the recent method used is reconfiguration. Distribution feeder reconfiguration can be used as a planning toll as well as a real time control tool in demand side management. Feeder reconfiguration means altering the topology structure of distribution feeders by changing open/close status of the sectionalizing and tie switches. 2

3 Feeder reconfiguration allows the transfer of loads form heavily loaded feeders (or transformers) to relatively less heavily loaded feeders (or transformers). Such transfers are effective not only in terms of altering the level of loads on the feeders being switched, but also in improving the voltage profile along the feeders and effecting reductions in the overall system power losses. Meanwhile, the installation of reconfiguration network is much simpler and cost efficient compared to other techniques. In general, reconfiguration have two primary objectives which are to provide the maximum amount of electrical supply to the end customers and reconfigure the network system automatically as soon as the problems arise. Thus, various reconfiguration methods have been proposed to solve the power loss problem and each method has the respective advantages and disadvantages. Objectives: In the present work, a simple approach for distribution reconfiguration was proposed standard switching indices are used for network reconfiguration and the algorithm is tested on a standard 32-bus system which has been taken as the benchmark problem for network reconfiguration in many IEEE papers. Also the algorithm is implemented on a typical 11kv distribution system which is radiating from main receiving station shivamogga.. Methodology: All the tie switches are closed in the network to form as many loops as the number of tie switches. In the meshed network each loop has a best opening point for minimum loss. By opening that switch, radial topology in that loop is regained. The procedure is repeated for all other loops. The switching indices are obtained for all the branches in the looped state. The node voltages and line parameters were used to define the indices. The voltage index: µ v: Minimizing R ij ( V i -V j Y ij ) 2,it can be seen that low voltage drop yields low loss. A voltage index µv can be defined for a particular branch N (from i to j) by µ v (n) = exp- ω (ΔVV nn ) 2 where Vn: the voltage drop between two terminals of branch N, (ΔV 2 av ) V 2 av : the mean square voltage drop of all branches for chosen loop ω : Weighing Factor The ohmic index µ L : Line constants R and Y can also be used to minimize Equation (1). Low current flow is expected for high R Y 2 value. The ohmic index µ L can be defined as µ L 3

4 (n) = exp- ω Where R av : The average branch resistance for a chosen loop, Y av : The average branch admittance for a chosen loop, ω:weighing Factor The decision index µ D: The decision index µ D can now be defined by using the product operation of indices µ v and µ L. Under normal operational state, the optimal decision can be obtained by: Max µ D (n) = Max { µ v (n) * µ L (n)} Weighing Factor w : weighing factor w is such that the weightage to open a branch decreases as we move away from the highest priority branch in either direction of the loop starting from the highest priority branch. The branch in the critical region, which has lower active losses, is considered as the highest priority branch to be opened. The developed algorithm and flow chart are shown below Algorithm Read the network data, dg data and nodes of DG injection At the nodes of DG injection, modify the load data with DGs as power sinks i.e., negative load. Close all the switches to form meshed network and run AC load flow. From the load flow data, for all the loops identify the highest priority branches and assign weighing factors to all the branches. Compute the switching indices for all the branches of each loop; arrange them in the descending order. Starting from the loop near the source, open the branch with highest switching index and run the AC load flow. Check for constraint violation. If any constraint is violated, ignore that branch for opening and go to step 6. Retain the radial topology of the loop and repeat steps 6, 7 and 8 for all the loops in the network. Obtain the final reconfiguration report. 4

5 Flowchart 5

6 Results and conclusions: The proposed algorithm has been implemented to the 11kV distribution system which is radiating from Main Receiving Station Shivamogga. It is shown in fig1. It has two closed loops and the 119 & 120 are the tie switches. Fig 1 The results obtained using load flow analysis is shown in table1. Table 1 LOOP 1 LOOP- 2 Critical node Voltage at critical node Critical Branches 58,60 74,79 MW loss in Critical Branches Minimum loss branch

7 From the above table 58 and 74 are the minimum loss branches in the critical region and they are given the highest value of weighing factor. Switching indices for 11kV MRS system are shown in table 2 and 3 Table 2 Branch Voltage index Ohmic index Decision index

8 8 Table 3 Branches Voltage index Ohmic index Decision index

9 Analyzing the switching indices, it can be seen that branches 60 and 74 are the branches having highest decision index. By opening these branches, losses are reduced from MW to MW and the loss reduction is %. Discussion The initial losses without reconfiguration were MW. After reconfiguration the losses were reduced to MW and the loss reduction is %.The results are compared with results of many IEEE papers, and it has been found that the developed algorithm gives satisfactory results. The results are tabulated in table4 Table 4 Case Open switch Loss(MW) Loss reduction Initial network 120, Reconfiguration network 60, Conclusions: There are several operational schemes in power distribution systems and one of these is network reconfiguration. Feeder reconfiguration for loss reduction is a very important function of automated distribution system to reduce distribution feeder losses and improve system security. A new algorithm has been proposed in this work for network reconfiguration. In some existing algorithms, the solution is largely dependent upon selection of tie branches and if the tie branches are not at appropriate locations, the results could be far away from optimal solution. The new algorithm proposed in this work is independent of specifying the tie branches in the data. The proposed algorithm has been applied to standard a 32 bus system which has been considered as a benchmark problem in many IEEE papers. It is interesting to note that there is a reduction of 31.11% of technical losses in the reconfigured network. 9

10 The proposed algorithm has been implemented on a 11 KV distribution system which is radiating from a Main Receiving Station Shivamogga and it was found that the technical losses were reduced by 33.12% in the reconfigured network. Scope for future work: The implementation of this project assures loss minimization and thus maintaining balance in changing load. Accounting to its flexibility in implementation various improvisations can be adapted in its applications. MATLAB programming gives flexibility with changing load data. Considering the huge number of advantages that will be caused due to improved load factor as well as utility is benefited by saved energy ensures ample amount of scope and technological advancement for this project. The cost for generating units is considerably reduced. 10