Power Systems & Energy Engineering

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    DISTRIBUTION SYSTEM RELIABLITY IMPROVEMENT USING DISTRIBUTED GENERATION AND NETWORK RECONFIGURATION Case study: Arbaminch Distribution system
    (Hawassa University, 2021-10-22) MEKLIT GIRMA
    Power supply reliability is the basic issue for economic and technology development of the country. The sufficient or adequate and secure supply of power will assure the reliability of the system. Unreliability of the system occur due to high outage frequency and duration, system overload and unsecure system or protection system. When the distribution system is reliable, it has capacity to meet the demand of customer and operate under adverse condition. Arbaminch distribution system has encountered frequent power interruption and power quality problem. The interruptions are mainly caused by system overload and short circuit fault. The reliability of the distribution system is assessed based on the data from Ethiopian Electric Power Corporation. Arbaminich substation of feeder -05 is selected as case study, which has high rate of interruption. Feeder -05 has SAIDI value of 236.8386 Hr./cust. /yr. and SAIFI of 221.6338 f/cust. /yr. The reliability indexes values of feeder -05 are not within the ranges of bench marks of reliability requirement. This thesis focused on reliability improvement of distribution system with better placement of distributed generation and network reconfiguration. Particle swarm optimization algorithm is used for placement of DG, size and network reconfiguration. The algorithm is done using MATLAB 2016 software. Based on the availability in the area, efficiency, cost and emission level, Solar and Microturbine sources are used as distributed generation. The suitable site and size of DG are found at bus 10 with suitable size 4.5 MW. For network reconfiguration sectionalizing switch is used. Before reconfiguration the switch was placed at bus 20, 21, 22,23 and 24. During network reconfiguration switch changed to bus 3, 4,12,24 and 31. The reliability indices SAFI, SAIDI and EENS value improved by 82.81%,78.89% and 78.10% respectively after DG with reconfiguration used. Expected interruption cost before applying the proposed method is 9,758,852$ /year. After the proposed method used expected interruption cost reduced to 2,995,270$ /year. This indicates that, 6,763,582 $/year is saved after using the proposed techniques
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    IDENTIFICATION, CLASSIFICATION AND MITIGATION OF POWER QUALITY ISSUES IN DISTRIBUTION NETWORK USING STOCKWELL TRANSFORM AND DISTRIBUTION STATIC COMPENSATOR (A CASE STUDY OF YIRGALEM SUBSTATION)
    (Hawassa University, 2022-12-23) Epaphros Mengistu
    Power quality has become a crucial concern recently due to the increase of the consumption of electrical load and the increment in the use of sensitive devices connected to power systems. In spite of that, complexity in modern daily life and the increased usage of semiconductors make non linear load a real threat to power quality level. In order that maintain power quality and to ensure its reliability, power quality disturbances must be identified and classified correctly and precisely. Thus, identification algorithms support decision makers to identified and mitigate the disturbance, and protect the power network from a high level of financial loss. In this thesis study identification, classification and mitigation of power quality issues in Awada industry zone. The measured voltage and current harmonic distortion levels are compared with the IEEE 519-2014 and IEC 61000-2-2 / -3-4 standards. The harmonic voltage distortion level in the factory has found to be well under the limits set by these standards while the current harmonic distortion levels on one of the transformer among four transform exceeds the limits with a maximum percentage total harmonic distortion current value of up to 23.09%. First, an identification process covering the most important and common power quality issues for further analyzed and discussed. Then after, most of the powerful processing algorithms in addition to support vector machine technique was investigated and their results are discussed. SVM then classify complex data and enhancing the evaluation process. This method achieved a sufficient detection algorithm, which overcame the Wavelet, Fourier and Hilbert limitations and resulted in an overall accuracy of 91.08%, 88.91% and 86.8% respectively. This resulted in a substantial improvement in terms of overall accuracy, with more than 97.1% when using Stockwell transform. In addition to the average classification accuracy, other common performance measures computed from the confusion matrix also presented and highest average accuracy of SVM is 98.3%. For mitigating, the current harmonic distortion level in the industry a D-STATCOM in current control mode is designed. The performance of the D-STATCOM is evaluated by simulating the distribution network with and without D-STATCOM. The simulation results show that the source current becomes pure sinusoidal and in-phase with the source voltage within 0.02 second and THDI reduced to 4.36% after the enabled of the D-STATCOM in the system
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    REACTIVE POWER COMPENSATION AND LOAD FREQUENCY CONTROL OF GRID CONNECTED MICRO GRID SYSTEM USING STATIC VAR COMPENSATOR (CASE STUDY: DILLA SUBSTATION)
    (Hawassa University, 2021-10-28) KUMILACHEW CHANE
    In the modern power system, reactive power compensation and load frequency control are two of the main issues. The aim of this thesis is to study reactive power compensation and load frequency control of the grid-connected micro grid system (GCMG) under variable load .In this work, an Artificial Neural Network based Static VAR compensator (ANN-SVC) and Load Frequency Controller (LFC) will be proposed for reactive power compensation and load frequency control of the grid-connected micro grid system, The artificial neural network (ANN) is used to control the the SVC gete signal for proper controlling of the thyristor valve in the circulated system current management. Power system Planning and management provide the strategy for reactive power compensation and load frequency disturbance control. The ANN-controlled SVC is used for managing and compensating of reactive power in the system and LFCis control the system load frequency disturbance and the LFC controlling loop component is control and managed by ANN signal for proper controlling of the load frequency error. The real and reactive powers before applying the SVC at the peak load conditions are 40.56MW and 27.16MVAr, respectively, before reactive power compensation. During contingency conditions, the real and reactive powers are 36.03MW and 30.42MVAr, respectively, and the frequency is highly disturbed for a fraction of a second, but after compensation, the real power is improved to 50.54MW, while the reactive power is reduced to 17.34MVAr. Therefore, real power is improved by 52.18% while reactive power is compensated by 87.02%. The steady-state load frequency error is reduced by 95%, while the system power factor is improved by 94%. A detailed comparative analysis of the proposed ANN-based SVC with the fuzzy-based and multi-objective fire fly (MOFA) algorithm SVC is presented, which shows that the ANN-based SVC has better performance, fast and accuracy, in case of the above justification ANN is more prifereble than MOFA and FUZZY algorithem. The general GCMG structure with the compensation and controlling process was designed by ETAP and MATLAB/Simulink
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    OPTIMAL PLACEMENT AND SIZING OF UNIFIED POWER FLOW CONTROLLER (UPFC) FOR VOLTAGE STABILITY ENHANCEMENT (CASE STUDY: GERD TO HOLETA 500/400 KV TRANSMISSION LINE NETWORK)
    (Hawassa University, 2025-10-26) GETAHUN SISAY
    The GERD to HOLETA 500/400 KV transmission line network was assessed to determine the optimal location and size for a Unified Power Flow Controller (UPFC) to enhance voltage stability. Due to the long transmission path and rising load demand, system components have become overloaded, causing power outages. To evaluate the current power system conditions, the Newton-Raphson load flow technique was used in the power flow model. The voltage stability index shows signs of instability, and load flow analysis reveals that all bus voltages, except for the slack bus, fall outside the acceptable range. Active and reactive power losses on the transmission line are 0.491 MW and 0.4689 MVAR, respectively; while the systems rated capacity is 2591 MW and 1255 MVAR. The minimum required voltage is 0.95 pu, but the actual minimum voltage magnitude and stability are 0.872 pu and 0.5262 pu, respectively. UPFCs, as reactive power compensation devices, are proven to enhance voltage stability, power losses, and voltage profiles. The UPFC was sized and placed using Grey Wolf Optimization (GWO) to minimize power losses, improve voltage stability, and optimize the voltage profile. The optimal UPFC size is 757.5 KVAR, and the best location is bus 3. With UPFC compensation, the bus’s minimum voltage magnitude and stability improve to 0.9668 pu and 0.83477 pu, respectively, while active and reactive power losses decrease to 0.1655 MW and 0.03302 MVAR. After implementing UPFC compensation, the annual energy loss cost is reduced from 10.343 million Birr to3 .486million Birr, and the total cost of a 757.5 KVAR, UPFC is 5.708 million birr including installation cost for resulting in a savings of 1.142 million Birr and a payback period of 12 months. The economic analysis confirms the solution is both effective and cost-efficient
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    ENHANCING THE RELIABILITY OF DISTRIBUTION SYSTEM THROUGH RENEWABLE ENERGY RESOURCES (CASE STUDY: GUDER TOWN DISTRIBUTION SYSTEM
    (Hawassa University, 2024-10-25) FIRAOL KASAHUN MENGESHA
    The distribution system connects high-voltage transmission networks with end-users. Most of the time, power plants are situated distant from the consumer's location, resulting in large power losses in both the distribution and transmission systems, However, distribution system losses are typically greater than transmission line side losses. The main objective of this study is to reduce power losses and enhance system reliability using Distributed Generation (DG) in the case of the Guder Substation. The Guder Substation has three feeder lines that provide energy for different customers. From these feeders, the Guder town feeder has been chosen since it is frequently interrupted. The chosen feeder has been modeled in ETAP software, and simulation results have been obtained with both ETAP and MATLAB software. The results show that the feeder has a power loss of 611.9843 KW and 323.8237 kVar active and reactive, respectively. Additionally, the study investigates the existing reliability indices of SAIFI, SAIDI, and EENS, which have values of 303.7458 f/cust.yr, 306.4240 hr/cust.yr, and 2368.307 MWhr/yr, respectively. Particle Swarm Optimization algorithm has been suggested to decide the best size and position of DG. After renewable Distributed Generation penetrated the network, the real and reactive power loss reduced from 611.9843 KW and 323.8237 kVar to 302.75 KW and 132.34 kVar, respectively. Additionally, the SAIFI, SAIDI, and EENS system reliability indices were enhanced from 303.7458 f/cust.yr, 306.4240 hr/cust.yr, and 2368.307 MWhr/yr to 27.4968 f/cust.yr, 13.650 hr/cust.yr, and 111.758 MWh/yr, respectively. Finally, reliability indices and line losses before and after Distributed Generations penetrated the network are compared. In general, the simulation results indicate that the suggested method is efficient in maintaining system reliability and minimizing power losses
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    DISTRIBUTION SYSTEM RELIABILITY ASSESSMENT AND ENHANCEMENT BY USING TIE SWITCHES AND SECTIONALIZER’S (CASE STUDY: BULE HORA DISTRIBUTION SYSTEM)
    (Hawassa University, 2022-10-22) ABABO BIKILA
    The majority of outage events experienced by customers are due to electrical distribution failures. Increasing distribution network reliability is a necessity in order to reduce interruption events Unreliable electric power distribution affects daily activity and drags the modern lifestyle. Basically, Power Distribution Reliability has been a major challenge in Bule hora city. The interruptions are caused mainly by the short circuit (SC) and earth fault (EF). Bule hora substation’s System Average Interruption Frequency Index (SAIFI) and System Average Interruption Duration Index (SAIDI) are 341.46 interruptions per customer per year and 666.82 hours per customer per year, respectively. Bule hora substation is not reliable by the standard of Ethiopian Electric Agency (EEA) which has set SAIFI as equal to 20 interruptions per customer per year and SAIDI which is around 25 hours per customer per year. Thus, the objective of the study is to assess the reliability of the existing distribution system and suggest solutions for reliability improvement in heuristic techniques. To limit the scope of the study, 15 kV Bule hora city feeder of the substation has been chosen for reliability enhancement measures. The historical outage interruption data of years 2009-2011 E.C has been used as a base year. The study has evaluated four different mitigation cases to improve the system reliability. From the mitigation cases with the lowest SAIDI, SAIFI and Expected Energy Not Supplied (EENS) at a reasonable cost has been selected. The simulation results have been done with the help of Electrical Transient Analysis Program (ETAP 16.0) software. The result of this thesis work reveals that the reliability of the system has been improved significantly by assessing reliability enhancement solutions that are justified economically and technically. Hence, the overall reliability of Bule hora city feeder indices SAIFI by 83.23%, SAIDI by 89.48% and EENS by 97.51%, have been improved as compared with the existing system for the simulated best option. The economic analysis shows that the selected solution results in a cost saving of 2,105,530.3 ETB per year from the unsold energy of one feeder only with 1.48 payback period investment. Satisfaction of the society has been considered as a priceless benefit as well
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    RELIABILITY ASSESSMENT AND ENHANCEMENT OF POWER DISTRIBUTION NETWORK BY OPTIMAL PLACEMENT OF SECTIONALIZERS (CASE:-STUDY ON ALABA DISTRIBUTION SUBSTATION
    (Hawassa University, 2023-04-18) YESHIWAS ALEMU
    Electrical power distribution unreliability reduces user power consumption and seriously affects day today activities. This thesis tries to assess reliability and mitigation strategy of the Alaba distribution substation which has faced frequent power interruption problem. 15kv Durame distribution feeder, according to the last three years consecutive data, has high interruption problem among the four feeders of Alaba distribution substation. The interruptions mainly caused by the earth fault and short circuit. There are also planned outages for operation and maintenance purpose. The feeder‟s System Average Interruption Frequency Index (SAIFI) and System Average Interruption Duration Index (SAIDI) are 167.79 interruptions per customer per year and 218.93 hours per customer per year, respectively calculated by Monte Carlo simulation. The Feeder is not reliable compared with Ethiopia Electric Agency (EEA) standard which has set SAIFI as equal to 20 interruptions per customer per year and SAIDI which is around 25 hours per customer per year. It is required to find best solution for enhancement of reliability. Therefore, the objective of the study is to enhancement the reliability of the distribution system by determination and optimal placement of sectionalizer switches by using whale optimization algorithm techniques and compared with particle swarm optimization. The historical outage interruption data of years 2019 to 2021G.C has been used as a base year. The reliability indices calculated by Monte Carlo simulation Algorithm techniques have been done with the help of Matlab 2016a software. Electrical Transient Analysis programs (ETAPS 16.0.0) software has been used for modeling existing system. The reliability of distribution system has improved by optimal placement sectionalizer switches. Therefore, the overall reliability of Durame city feeder indices SAIFI by 85.98% (Decrease from 167.79 to 23.52 interruption per customer per year), SAIDI by 80.93% (Decrease from 218.93 to 41.73 hours per customers per year) EENS by 67 % (Decrease from 2,224.79 to 734.199 Megawatt hours per year), and Cost of EENS by 66.44% (Decrease From 4,449,590.4 to 1,468,398 Birr per year) has been improved as compared with the existing system. The economic analysis indicates that the selected solution results in a cost saving of 2,981,192.4 ETB per year from the unsold energy of one feeder only with 0.79 year payback period investment.
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    Assessment & Allocation of Transmission Losses & Costs under N-1 Contingency Condition
    (Hawassa University, 2016-08-17) Rahel Dawit
    Traditionally electricity supply industry (ESI) was monopolistic in nature with generation; transmission and distribution owned by government. Now in all over the world electricity market is restructured. All the three major areas i.e. generation, transmission and distribution are now working as separate companies namely Generating Companies (GENCO), Transmission Companies (TRANSCO) and Distribution Companies (DISCOMs). Under this environment the question of loss allocation is also very much important because no one want to bear this loss. Contingency conditions are normal practices in real power system and this brings transmission reliability margin into the picture. Further under contingency the value of losses in certain lines is increased due to extra flows in these lines. Hence transmission loss assessments, allocation and pricing with consideration of contingency are significant issues in restructured electricity market. Due to this reason a methodology for transmission loss assessment, allocation and pricing with consideration of N-1 contingent maximum flow condition has been developed. For finding contingent loss novel reliability factors is introduced. By using this factor optimal losses are calculated. After calculating these losses by using Bialek’s tracing these losses are allocated to generators and loads. After that by using MW-cost methodology transmission loss cost is allocated to the generators and demands. Sample 6 bus and IEEE 14 bus system are used for showing the feasibility of this method
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    DISTRIBUTION NETWORK OPTIMIZATION BY OPTIMAL SIZING AND PLACEMENT OF D-STATCOM USING TEACHING AND LEARNING BASED OPTIMIZATION ALGORITHM (CASE STUDY: YIRGALEM SUBSTATION)
    (Hawassa University, 2021-10-18) AZMERAW ARGAW
    Distribution system is part of an electric power system which links the high voltage transmission networks with the end consumers. This work offers the way of improving the performance of the distribution network by improving voltage profile and reduction of power loss via injecting reactive power through the network. Optimal siting and sizing of custom power devices in power distribution networks maximizes voltage profile, compensates reactive power, minimizes power loss and enhances voltage profile. The search for optimal size and locations of these devices in radial distribution networks is challenging and requiring robust scheduling. This study is conducted with a focus on Aposto feeder of Yirgalem distribution network. The voltage profiles of most buses are not in an acceptable range, and the voltage stability index of the buses shows that network is prone to voltage stability problem. In this study, it is aimed to find the best optimal D-STATCOM sizing and placement by using Teaching and Learning Based Optimization (TLBO). Results obtained have been compared with those of the conventional optimization techniques reported in literature. For the Aposto feeder 62-bus network, the optimal location and size of D-STATCOM were determined at bus 38 with 1019.18 𝑘𝑉𝑎𝑟, at bus 28 with 942.96 𝑘𝑉𝑎𝑟, at bus 39 with 1074 𝑘𝑉𝑎𝑟 and at bus 25 with 1184 𝑘𝑉𝑎𝑟 by the GA, PSO, GREY WOLF and WHALE OPTIMIZATION method respectively. While the TLBO approach obtained the optimal site and size of the D-STATCOM in the network to be bus 51 and 871.4 𝐾𝑉𝑎𝑟 at normal load condition. As stated, the TLBO method performs better in terms of reducing both real and reactive power losses. The real power loss percentage reduction of the test system is 27.09%, 69.19% and 70.24% whereas the reactive power loss percentage reduction is 30.97%, 68.85% and 69.85% for light load, normal load, and heavy load respectively. Also, the minimum voltage level in the worst case is significantly enhanced from 0.93pu to 0.988pu. The model has been formulated to minimize the total cost of the network by determining the optima of the substation locations and power, the load transfers between the demand centers, the feeder routes and the load flow in the network subject to a set of constraints. As per the economic evaluations, the proposed solution is cost-effective. In this research D-STATCOM control is developed based on artificial intelligent (AI) using artificial neural network (ANN), which depends on optimum values obtained by TLBO. Generally, the simulation results show that the proposed technique is effective to maintain all buses voltage magnitude within the IEEE acceptable limit and to reduce power losses significantly
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    CUSTOMIZED INTERLINE POWER FLOW CONTROLLER FOR VOLTAGE PROFILE IMPROVEMENT AND POWER LOSS MINIMIZATION OF TRANSMISSION LINE (CASE STUDY: SOUTHERN REGION FROM SHASHEMENE TO BUKULUGUMA TRANSMISSION SYSTEM)
    (Hawassa University, 2024-10-22) ASRAT LEMMA
    An electrical system is a collection of components that are used to supply, transmit, and consume electricity. Transmission lines effectively transfer the electricity produced by different power plants. Nevertheless, the generated electricity is not entirely supplied to customers because of voltage drop and power loss. Uncontrolled bus voltage profile caused problems for industries that were developing quickly. Interline power flow controller (IPFC) is a type of flexible AC transmission system (FACTs) devices applicable to reduce power loss and enhance voltage profiles of the transmission networks from Shashemene to Bukuluguma transmission system. Load flow analysis on nine buses were performed by Newton Raphson load flow analysis technique using MATLAB R2016a. The analysis showed that out of nine buses four buses are out of voltage limit. On the system as a whole, there has been a loss of 8% real power and 10.42% MVAr reactive power, or 7.322MW and 4.530 MVAr, respectively. To minimize the loss problems, grey wolf optimization (GWO) techniques were proposed to search optimal place and size of interline power flow controller (IPFC), placed on bus 5, and sized 27MVAr. GWO techniques are compared with Antlion optimization, but GWO gives a good performance. After analysis data 4 buses bus number 4, 7, 8, and 9 are out of permissible values, the remaining buses are within acceptable limits. GWO techniques suggest implementing the lowest voltage stability index bus. After installing IPFC in optimal power flow place the network problem is improved by GWO 6.1% and ALO 3.9%, the lowest case voltage profile improved from 0.937pu to 0.978pu and 59.7% of active power and 40% of reactive power are saved. Finally, the reduction result suggest that the recommended approach is operative to regulate all buses voltage magnitudes within the NEC and IEEE permissible boundary and to minimize power loss considerably