Bonfring International Journal of Power Systems and Integrated Circuits, Vol. 7, No. 2, June 2017 19 Feeder Automation and its Reliability Assessment on the Basis of Cost Analysis for the Distribution of Feeders in Power System Planning Jonh Smith and John Sebastian Abstract--- At present, automating a distributing system is an efficient means of providing a trustworthy system. There is a rising attention in the quantitative assessment of power system reliability worth and its application to cost-benefit evaluation in power system planning. Therefore, this paper takes care of automating a system using two stage restorations (partial automation). It formulates a feeder automation system using the idea of optimal placement of switches that can be applied to electrical distribution systems for high economictechnical efficiency. Reliability is effectively analyzed and evaluated when feeder automation is applied to distribution and its worth is subsequently assessed. Moreover, it looks into a case study involving reliability and economic evaluation of Urban, Rural and Industrial Feeders and illustrates a most feasible conclusion. Keywords--- Reliability Evaluation, Distribution Automation, Partial Automation or Two Stage Restoration, Optimum Placement of Switches, Feeder Automation, Reliability Evaluation. E I. INTRODUCTION LECTRICAL energy plays a vital role in the economic and social development of any country. This requires electric power utilities to provide uninterrupted power supply to their customers. Hence the basic aim of every electric power utility is to meet its energy and load demand at the lowest possible cost to the customers while maintaining acceptable levels of quality and continuity of supply. The two important aspects of continuity and quality of supply, together with proper planning, design, control, operation and maintenance of an electric power network, usually gives us the reliability assessment of the system. The worth of reliability refers to the value of continuous electrical service. It is more easily estimated and expressed, however, as a function of the costs resulting from the lack of such service. This implies that the losses and damages resulting from interruptions in electrical supply might represent the amount customers and utility management would be willing to pay to prevent such power outages. The worth of reliability can therefore be expressed in terms of customer outage costs. II. CONCEPTS INVOLVED Distribution Automation is basically about automating a distribution system and providing a reliable, efficient supply to meet the increasing demand. It refers to automation of repetitive tasks on the electric utility s distribution system. In DA system, normally closed sectionalizing switches (SS) and normally open route switches (RS) are used to automate the distribution feeder function. These switches restrict the extent of distribution caused by long power interruption when properly positioned. [15] Any system is basically judged based on its Reliability. The reliability of an electrical power distribution system can be increased by automation of its feeder and associated parts. Automated and remotely controlled service restoration can eliminate the need to perform switching operations manually and can have a significant effect on the system reliability. Partial Automation is a viable switching/restoration strategy when a feeder contains automated devices. Most distribution systems either have no automated devices or are partially automated with a combination of manual and automated devices. In this strategy, a first stage quickly restores a limited set of customers using automated switches. A later stage restores additional customers using manual switches. Hence this is also known as Two Stage Restoration. [3] Optimum Placement Of Switches Any successful system is meant to be both reliable and cost effective. More usage of automated switches will increase the cost tremendously. Hence usage of optimum number of switches placed at most logical and probable areas of the feeder could give us a more reliable and economical distribution system. Placement of switches on a lateral can be decided based on the average number of load points distributed for each switch. This provides minimum loss and fast restoration of power supply to remaining parts of the system. We can look into the application and its respective effect and the advantages in getting a more reliable n cost effective system in the case study done below. Reliability Concepts Any system is basically assessed on its reliability. Reliability can be evaluated and analyzed using Reliability Indices. Load point indices and overall system indices together are classified as reliability indices. [2] Jonh Smith, York University, Canada. John Sebastian, University of Jaén, Spain. DOI:10.9756/BIJPSIC.8336
Bonfring International Journal of Power Systems and Integrated Circuits, Vol. 7, No. 2, June 2017 20 III. COST CONCEPTS Any System is said to be successful only when its reliable and is provided to the customers with reasonable cost benefits. Hence economic evaluation of a system helps for a better functioning of a system. Economic evaluation or reliability worth of a system can be estimated and studied with the following concepts. [5] Customer Damage Functions (CDF) customer interruption costs can be found using customer damage functions. The CDF can be determined for a given customer type and aggregated to produce sector customer damage functions for the various classes of customers in the system. The sector CDF (SCDF) can be aggregated at any particular load point in the system to produce a composite customer damage function (CCDF) at that load point. The reliability worth can be analyzed using Expected Interruption Cost (ECOST) which helps in assessing its worth and decide on the most optimal feeder. [5] IV. STEPS FOLLOWED TO CALCULATE THE RELIABILITY & ITS WORTH Figure 1: Flowchart Explaining the Reliability Assessment and Evaluating Its Worth
Bonfring International Journal of Power Systems and Integrated Circuits, Vol. 7, No. 2, June 2017 21 V. CASE STUDY ON DIFFERENT TYPES OF DISTRIBUTION SYSTEMS A. Reliability Assessment & Economic Evaluation of Urban Feeder Taking a 33/11 KV Urban radial distribution system from Moulali Substation, Hyderabad, Andhra Pradesh, into consideration, reliability of this system is assessed and a most feasible system is proposed. This basically consists of circuit breakers, feeders, sectionalizing switches, load points and a tie line switch. The system consists of 19 distribution transformers with 550 customers with an overall average load consumption of 313.173 MW. This Urban feeder consists of customers related to Figure 2: 33/11 KV Urban Distribution Feeder domestic loads, commercial loads and industrial loads and the customer data and network data of each different load can be studied at [10]. Feeder Modeling and Reliability Evaluation The feeder is configured and its reliability is assessed following the steps involved in the flow chart discussed before. The reliability of the feeder can be studied using the reliability indices obtained. Table 1: Reliability Assessment of Urban Feeder for the Following Configurations Combination of Switches SAIFI SAIDI CAIDI ASAI ENS AENS Switches 12345678 in AAAMMMMM Configuration 0.4852 10.0867 20.7887 0.99885 3093.63 1213.19 Switches 12568 in AAAMM Configuration 0.4852 13.1872 27.1789 0.99849 4063.9 1593.68 Switches 12358 in AAAMM Configuration 0.4852 15.8894 32.7482 0.99819 4789.77 1878.34 Switches 13568 in MMAAA Configuration 0.4852 13.4261 27.6712 0.99847 4313.39 1691.53 Switches 12568 in MMAAA Configuration 0.4852 10.8137 22.2871 0.99877 3472.87 1361.91 Analyzing the Reliability Worth Following the steps involved in the flow chart, the feeder is analyzed to see whether it is cost benefited. The reliability worth is estimated with the help of ECOST value obtained. The economic evaluation can be studied with the help of following data provided at the tables.
Bonfring International Journal of Power Systems and Integrated Circuits, Vol. 7, No. 2, June 2017 22 Table 2: Estimated ECOST & Analyzing Feeder s Worth Load Point ENS (MWh/yr) ECOST (Rs/yr) LP1 78.053516 0.7066333 LP2 318.7241 0.7729563 LP3 266.97608 0.0971189 LP4 248.81027 0.6034042 LP5 69.214203 0.1057489 LP6 256.35391 0.7625772 LP7 155.5728 0.7345765 LP8 30.069273 0.095414 LP9 13.703999 0.0167653 LP10 215.58506 0.4186413 LP11 462.05776 0.5652756 LP12 305.53479 0.5933133 LP13 241.64411 0.469245 LP14 21.163277 0.0167885 LP15 24.762047 0.0495013 LP16 288.51713 0.6914939 LP17 375.91525 2.252406 LP18 26.11653 0.0156485 LP19 74.099329 0.1775951 3472.8734 9.145103 B. Reliability Assessment & Economical Evaluation of Rural Feeder System Description Figure 3: 33/11 KV Rural Distribution Feeder
Bonfring International Journal of Power Systems and Integrated Circuits, Vol. 7, No. 2, June 2017 23 Taking a 33/11 KV Rural radial distribution system from Ghatkesar Substation, Hyderabad, Andhra Pradesh, into consideration, reliability of this system is assessed and a most feasible system is proposed. This basically consists of circuit breakers, feeders, sectionalizing switches, distribution transformers, load points and normally open tie-switch. The system consists of 21 distribution transformers with 422 customers with an overall average load consumption of 72.304 MW. This Rural feeder consists of customers related to domestic loads, commercial loads and small scale industrial loads and the customer data and network data of each different load can be studied at [9]. Feeder Modeling and Reliability Evaluation The feeder is configured and its reliability is assessed following the steps involved in the flow chart discussed before. The reliability of the feeder can be studied using the reliability indices obtained. Table 3: Reliability Assessment of Rural Feeder for the Following Configurations Combination of Switches SAIFI SAIDI CAIDI ASAI ENS AENS Switches 123456 in AAMMMA Configuration 0.6712 11.514863 17.155635 0.9986855 793.87081 1881.2104 Switches 13456 in AMMAA Configuration 0.6712 17.951454 26.745313 0.9979507 1171.109 2775.1399 Switches 12456 in AAMMA Configuration 0.6712 16.259851 24.225046 0.9981439 1071.1684 2538.3137 Switches 12356 in AAMMA Configuration 0.6712 14.293271 21.295099 0.9983683 957.76952 2269.596 Switches 12346 in AAMMA Configuration 0.6712 15.728719 23.433729 0.9982045 1196.9865 2836.4608 Switches 12345 in AAMMA Configuration 0.6712 13.066602 19.467524 0.9985084 1060.8146 2513.7786 Analyzing the Reliability Worth Following the steps involved in the flow chart, the feeder is analyzed to see whether it is cost benefited. The reliability Table 4: Estimated ECOST & Analyzing Feeder s Worth Load Point ENS(MWh/yr) ECOST(Rs/yr) worth is estimated with the help of ECOST value obtained. The economic evaluation can be studied with the help of following data provided at the tables. P1 11.394058 0.0274335 LP2 16.746971 0.0403217 LP3 33.634137 0.0809809 LP4 81.721139 0.0780794 LP5 121.41065 0.294649 LP6 74.614067 0.1810793 LP7 122.39634 0.0813185 LP8 11.2719 0.0074889 LP9 21.297477 0.056599 LP10 43.38307 0.0726343 LP11 20.655987 0.0548942 LP12 113.91034 0.3027219 LP13 32.167122 0.0780657 LP14 17.853764 0.0433289 LP15 14.08724 0.0460293 LP16 77.799131 0.2542046 LP17 81.837474 0.6791102 LP18 9.0181576 0.0087797 LP19 16.03506 0.015611 LP20 25.465976 0.0624771 LP21 11.069444 0.0431068 957.76952 2.5089139
Bonfring International Journal of Power Systems and Integrated Circuits, Vol. 7, No. 2, June 2017 24 C. Reliability Assessment & Economic Evaluation of Industrial Feeder System Description Taking a 33/11 KV Industrial radial distribution system from Nacharam Substation, Hyderabad, Andhra Pradesh, into consideration, reliability of this system is assessed and a most feasible system is proposed. This basically consists of circuit breakers, feeders, sectionalizing switches, distribution transformers, load points and normally open tie-switch. The system consists of 32 distribution transformers with 42 customers with an overall average load consumption of 460.207 MW. This Industrial feeder consists of customers related to Figure 4: 33/11 KV Industrial Distribution Feeder industrial loads only. The loads comprise of both small scale & large scale industries and the customer data and network data of each different loads can be studied at [9] Feeder Modeling and Reliability Evaluation The feeder is configured and its reliability is assessed following the steps involved in the flow chart discussed before. The reliability of the feeder can be studied using the reliability indices obtained. Table 5: Reliability Assessment of Industrial Feeder for the Following Configurations Combination of Switches SAIFI SAIDI CAIDI ASAI ENS AENS Switches 12345678 in AAMMMAMM Configuration 0.11285 0.9026887 7.9990134 0.999897 403975.64 8416.1592 Switches 12568 in AAMAM Configuration 0.11285 1.6762887 14.854131 0.9998086 750170.31 15628.548 Switches 12358 in AAAMM Configuration 0.11285 1.9126678 16.948762 0.9997817 844395.09 17591.564 Switches 13568 in AAMAM Configuration 0.11285 1.496908 13.264581 0.9998291 704760.61 14682.513 Switches 12568 in AAMMA Configuration 0.11285 1.5666664 13.882733 0.9998288 632322.29 13173.381 Analyzing the Reliability Worth Following the steps involved in the flow chart, the feeder is analyzed to see whether it is cost benefited. The reliability worth is estimated with the help of ECOST value obtained. The economic evaluation can be studied with the help of following data provided at the tables.
Bonfring International Journal of Power Systems and Integrated Circuits, Vol. 7, No. 2, June 2017 25 Table 6: Estimated ECOST & analyzing feeder s worth Load Point ENS(MWh/yr) ECOST(Rs/yr) LP1 19.000681 0.0655205 LP2 1.4600509 0.001982426 LP3 39.416542 0.2123767 LP4 5.2270413 0.0249728 LP5 46.232145 0.0706814 LP6 10.967912 0.0104801 LP7 4.21184 0.004024512 LP8 9.0651876 0.0054571 LP9 1.0596399 0.00052396 LP10 1.1373595 0.00056239 LP11 5.7417697 0.004506561 LP12 106.78289 0.4190551 LP13 29.643379 0.0372261 LP14 3.9219945 0.003078268 LP15 1.4861497 0.000734857 LP16 2.5192512 0.00494323 LP17 56.974126 0.0715479 LP18 9.5447612 0.0912024 LP19 41.794532 0.2995174 LP20 5.0779256 0.0085891 LP21 62.080345 0.7875472 LP22 11.109337 0.0469774 LP23 17.847945 0.0483025 LP24 5.7822755 0.004436634 LP25 12.772585 0.0156803 LP26 70.360714 0.1349662 LP27 6.7324146 0.0051657 LP28 7.7077616 0.005914 LP29 1.1459842 0.000879293 LP30 6.1681483 0.0075723 LP31 28.88617 0.0554096 LP32 0.4634352 0.001777927 632.32229 2.451612 VI. RESULTS & CONCLUSION compared under different system controls such as manual control, under fully automated control and under partially The Reliability of all the three feeders are analyzed and automated control, as shown below. Table 7: Reliability Assessment & Economic Evaluation of Urban, Rural, Industrial Feeders Feeders ENS % ENS Total Ecost per Under Manual Control With Full Automation With Partial Automation Ecost MW Industrial 632.32229 4.7768 0.1866 0.1908 2.451612 0.5327 Urban 3472.87344 37.7564 1.5232 1.5401 9.145 2.9201 Rural 957.7695161 45.2349 1.8181 1.8397 2.5089139 3.4699
Bonfring International Journal of Power Systems and Integrated Circuits, Vol. 7, No. 2, June 2017 26 Figure 5: % ENS Assessment of Industrial, Urban & Rural Feeder Figure 6: Evaluation of Reliability Worth of Industrial, Urban & Rural Feeder By studying the above results, we can say that a system s reliability increases as we automate some of its functions and maintaining the system becomes much easier when compared to systems operated manually. Partial automation gives us a better distribution system which is both reliable and cost effective. Here Reliability Indices help us in gauging the reliability of a system and help us in improving the system s reliability for a better economical purpose where as Cost analysis gives us a precise idea on interruption costs and its effect on customers and utility. This also looks into how and on what factors the reliability of a system depends as we compare three different feeders such as Industrial, Urban and Rural distribution feeders. It also looks into how the interruption affects the reliability and its worth and how could we improve the reliability by decreasing the interruptions occurring at the feeder. These case studies conclude that two way restoration technique and optimal placement of switches concept helps in getting a more reliable and cost effective distribution system. [3] R.E. Brown and A.P. Hanson, Impact of two-stage service restoration on distribution reliability, IEEE trans. on power systems, Vol. 16, No. 4, Pp. 624-629, 2001. [4] R. Billinton and J.E. Billinton, Distribution System Reliability Indices, IEEE Transaction on Power Delivery, Vol. 4, No. 1, 1989. [5] Roy Billinton and R.N. Allan, Reliability Evaluation of Power Systems, IEEE Tutorial Course-Distribution Automation. [6] A. Chowdhury and D. Koval, Power Distribution system Reliability- Practical Methods and Applications, John Wiley & Sons, 2011 [7] R. Billinton and L. Goel, Overall adequacy assessment of an electric power system, IEEE Proc C (Generation, Transmission and Distribution), 1992. [8] R. Billinton, Evaluation of Reliability Worth in an electric power system, Reliability Engineering and System Safety, Vol. 46, 1994. [9] Richard E. Brown, Electric Power Distribution Reliability, CRC Press, 2008. [10] R.K. Subramaniam, G. Wacker and R. Billinton, Understanding commercial losses resulting from electric service interruptions, IEEE transactions on industry applications, Vol. 29, No. 1, Pp. 233-237, 1993. REFERENCES [1] R.N. Allan, R. Billinton, I. Sjarief, L. Goel and K.S. So, A reliability test system for educational purposes-basic distribution system data and results, IEEE Transactions on Power systems, Vol. 6, No. 2, Pp. 813-820, 1991. [2] F.T. Asr and A. Kazemi, Modeling the impact of an automated and control on the reliability distribution system, IEEE Electric Power Conference, 2008.