Power Systems & Energy Engineering

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/72

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Start date: 2022End date: 2022

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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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    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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    TRANSMISSION LINE VOLTAGE PROFILE IMPROVEMENT AND POWER LOSS REDUCTION BY OPTIMAL PLACEMENT OF STATIC SYNCHRONOUS COMPENSATOR USING TEACHING LEARNING BASED ALGORITHMS
    (Hawassa University, 2022-03-18) Mulye Getu
    The power transmission system transports electric power generated at generation plant to distribution system. The increasing power demand of customers causes the power transmission system to become stressed when connected to distribution system. This leads to voltage instability and, further to, transmission power loss, which can lead to power system malfunction and system collapse. Most bus voltages are not within acceptable limits, and the voltage index of the buses indicates that the network is prone to voltage instability issues. The objective of this thesis is to determine the best placement for a static synchronous compensator (STATCOM), which is one of the Flexible AC Transmission Systems (FACTS) devices, on the Alaba to Bukuluguma Transmission System network to minimize transmission line loss, improve voltage profile, and enhance power transfer capacity. The power flow analysis by Newton Raphson algorithm in MATLAB environment is used and Teaching Learning-based optimization techniques (TLBO) are adopted for optimal sizing and location of the device. The obtained results were compared to those reported in the literature for conventional optimization techniques. The optimal location and size of STATCOM for the Alaba to Bukuluguma transmission network were identified using the genetic algorithm (GA) and particle swarm optimization (PSO) methods accordingly, 25.8MVar at bus 6 and 25.5 MVar, at bus 5 respectively. According to the TLBO technique, bus 4 with 25MVar is the best placement and size of STATCOM in the network. The TLBO approach, as previously indicated, performs better in terms of reducing real and reactive power losses. The test system's real power loss reduction is 39.8 percent, while the reactive power loss reduction is 49.3 percent. In addition, the worst-case minimum voltage level has been enhanced from 0.878pu to 0.953pu. STATCOM control is established in this study utilizing artificial intelligence (AI) and an artificial neural network (ANN), which is based on TLBO's optimal values. In general, simulation results demonstrate that the suggested approach is effective in keeping all bus voltage magnitudes within the IEEE permissible limit while also drastically reducing power losses.
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    Impact of Distributed Generation on Distribution Network Protection scheme and Adaptive Protection Coordination using Harris’ Hawks Optimization
    (Hawassa University, 2022-12-27) ABENEZER KASSA USAMO
    The Modern Power System which has grown both in size and complexity, that means requires fast, accurate and reliable Protective schemes for protecting major equipment’s and to maintain system stability and reliability. Distribution networks are evolving into active meshed networks with bidirectional power flow as the penetration of distributed generation (DG) sources is increasing. Interconnecting DG to an existing distribution system provides various benefits to several entities as for example the owner, utility, and the final user. DG provides an enhanced power quality, higher reliability of the distribution system and can peak shaves and fill valleys. Penetration of a DG into an existing distribution system has many impacts on the system, with the power system protection being one of the major issues. This necessitates the use of directional relaying schemes in these emerging active distribution networks. However, conventional directional overcurrent (OC) protection will not be adequate to protect these networks against the stochastic nature of DGs and the changing network architectures. Hence, this study proposes an adaptive directional overcurrent relay algorithm that determines optimal protection settings according to varying fault currents and paths induced by the DGs in active meshed distribution networks. Location and technology of the DG sources are changed to study the effect that these changes may have on the coordination of protective directional over-current relays (DOCR). Results are compared to that of the normal case to investigate the impact of the DG on the short circuit currents flowing through different branches of the network to deduce the effect on protective devices. This study presents an adaptive protection coordination scheme for optimal coordination of DOCRs in interconnected power networks with the impact of DG. The used coordination technique is the Harris Hawks Optimization (HHO), selected due to adaptive & time-varying parameters allows HHO to handle difficulties of search including local optimal solution, multi modality & deceptive optima. Adaptive relaying describes protection schemes that adjust settings and/or logic of operations based on the prevailing conditions of the system. These adjustments can help to avoid relay miss-operation. Adjustments could include, but are not limited to, the logging of data for post-mortem analysis, communication throughout the system, as well changing relay parameters. Several concepts will be discussed, one of which will be implemented to prove the value of the new tools available. The optimal coordination of DOCR is find by with MATLAB code using HHO technique and the adaptive protection scheme model will develop in DIgSILENT/Power Factory. The results validate the ability of the proposed protection scheme to capture the uncertainties of the DGs and determine optimal protection settings, while ensuring minimal operating time
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    IDENTIFICATION, CLASSIFICATION AND MITIGATION OF POWER QUALITY ISSUES IN DISTRIBUTION NETWORK USING STOCKWELL TRANSFORM AND DISTRIBUTION STATIC COMPENSATOR
    (Hawassa University, 2022-10-16) 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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    IMPACT OF DISTRIBUTED GENERATION ON DISTRIBUTION NETWORK PROTECTION SCHEME AND ADAPTIVE PROTECTION COORDINATION USING HARRIS’ HAWKS OPTIMIZATION
    (Hawassa University, 2022-07-26) ABENEZER KASSA USAMO
    The Modern Power System which has grown both in size and complexity, that means requires fast, accurate and reliable Protective schemes for protecting major equipment’s and to maintain system stability and reliability. Distribution networks are evolving into active meshed networks with bidirectional power flow as the penetration of distributed generation (DG) sources is increasing. Interconnecting DG to an existing distribution system provides various benefits to several entities as for example the owner, utility, and the final user. DG provides an enhanced power quality, higher reliability of the distribution system and can peak shaves and fill valleys. Penetration of a DG into an existing distribution system has many impacts on the system, with the power system protection being one of the major issues. This necessitates the use of directional relaying schemes in these emerging active distribution networks. However, conventional directional overcurrent (OC) protection will not be adequate to protect these networks against the stochastic nature of DGs and the changing network architectures. Hence, this study proposes an adaptive directional overcurrent relay algorithm that determines optimal protection settings according to varying fault currents and paths induced by the DGs in active meshed distribution networks. Location and technology of the DG sources are changed to study the effect that these changes may have on the coordination of protective directional over-current relays (DOCR). Results are compared to that of the normal case to investigate the impact of the DG on the short circuit currents flowing through different branches of the network to deduce the effect on protective devices. This study presents an adaptive protection coordination scheme for optimal coordination of DOCRs in interconnected power networks with the impact of DG. The used coordination technique is the Harris Hawks Optimization (HHO), selected due to adaptive & time-varying parameters allows HHO to handle difficulties of search including local optimal solution, multi modality & deceptive optima. Adaptive relaying describes protection schemes that adjust settings and/or logic of operations based on the prevailing conditions of the system. These adjustments can help to avoid relay miss-operation. Adjustments could include, but are not limited to, the logging of data for post-mortem analysis, communication throughout the system, as well changing relay parameters. Several concepts will be discussed, one of which will be implemented to prove the value of the new tools available. The optimal coordination of DOCR is find by with MATLAB code using HHO technique and the adaptive protection scheme model will develop in DIgSILENT/Power Factory. The results validate the ability of the proposed protection scheme to capture the uncertainties of the DGs and determine optimal protection settings, while ensuring minimal operating time