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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.
ANALYSIS AND PRIDICTION OF METEOROLOGICAL DROUGHT USING STANDARDIZED PRECIPITATION INDEX: CASE STUDY OF EASTERN OROMIA
(Hawassa University, 2019-02-14)
Ethiopia is one of the most drought affected country in Africa and suffered from acute
drought many time in recent years. The objective of this study is to understand the
rainfall variation and conduct an in-depth analysis and prediction of drought for to
Eastern Oromia. Standardized precipitation index (SPI) was selected to characterize
drought condition in the region.
Drought characteristics at a time scale of 2-month, 3-month, 6month and 12-month were
computed separately for 22 selected rain gauge station. The most maximum drought
characteristics at 2-month, 3-month, 6-month and 12-month time scales have been found
in Hararegie over last 36 years (1979-2015). The spacial extent of drought and rainfall
variation were determined from SPI and CV values computed separately for each rainfall
have been interpolated between station in Arc view GIS environment. The rainfall
variation shows that the rainfall over the study area is highly variable and increases from
Arsi to East Harargie and in the recent last decade (2005-2015) the map of SIP-3 (Belg)
shows that a spacial extent drought over study area was irregular and there were no
period in recent decades (2005-2015) without drought at least mild drought and this
shows that the area is vulnerable to drought. The maximum intensity of (5.33) was
recorded at Fedis Station for SPI-3 (kiremt season) in a year 1996, maximum intensity of
(4.04) was recorded at Kobo Station in a year 1985 for SPI-3 (Belg season), maximum
intensity of (4.77 and 4.5) were recorded at Ticho Station for SPI-6 (both seasons) and
SPI-12 (annual) respectively.
The drought prediction was made until 2043, using the Representative Concentration Path
way (RCP) 8.5 Scenario.on the basis of the drought index measured by SPI. From the
analysis of the drought index through the RCP 8.5 Scenario, extreme drought intensity will
be more likely to occur. The long-term forecast (12-month period unit) showed that
extreme drought would occur severely at station Diksis Sude, Hirna and Adelle from 2035
to 2040 and need more attention for this area
INFESTATION AND EFFECTS OF ANISAKID NEMATODE PARASITES ON THE NILE TILAPIA (Oreochromis niloticus LINNAEUS, 1758) IN LAKE HAWASSA, ETHIOPIA
(HAWASSA UNIVERSITY, 2024-10) RIBKA MENTA BALCHA
Contraceacum species that is genus of Anisakid parasites is the most economically important internal fish parasite,that poses serious problem in culture and capture fisheries globally, as well as consumers. This investigation aimed to evaluate the infestations and certain effects of Contraceacum spp. on O. niloticus L. 1758) in Lake Hawassa. The study used a cross-sectional design from December 2023 to May 2024. A total of 180 O. niloticus were taken from the landing site. To assess the water quality, samples of water were taken fro amora gedel. Infestation peaked in February and April each with 56.6% and lowest in December (40.0%). However, highest intensity of Contracaecum spp. was in May (9.66%) and lowest in January with (4.20%). Prevalence of Contracaecum with sex of O. niloticus were statistically not significant.The size of O. niloticus and the presence of Contracaecum were positively correlated. Hematological effects of Contracaecum on O .niloticus between infested and non-infested group were significant (p<0.05) except for neutrophil count sand basophil (p>0.05). The results of the physicochemical parameters showed statistically significant difference with all parameters except ammonia that showed variation, but not statistically significant (p value=0.294). There were positive correlation between physicochemical parameters and the prevalence of Contracaecum, however, negative correlation with dissolved oxygen (r=-0.002). In conclusion, the temperature of the water influences whether the Contracaecum infestation is high or low, depending on the sampled months. Contracaecum parasite prevalence is also influenced by variations in physicochemical parameters. The high prevalence (37.3%) of Contraceacum spp. in muscles of O. niloticus as compared to varied various body organs indicates that consuming raw fish poses a significant health risk to humans. Therefore,it is crucial to eat the fish only well coocked form, at the encysted larvae present in fish muscle can be transmitted to human hosts.
EVALUATION OF THE EXISTING URBAN WATER SUPPLY SYSTEM: A CASE OF HARGEISA CITY, SOMALILAND
(Hawassa University, 2020-12-17) MOHAMOUD MOHAMED ISMAIL
Urban water supply and demand challenges are widespread problems in most of the developing countries such as Somaliland. This thesis paper focuses on the evaluation of the existing urban water supply system of Hargeisa, capital city of Somaliland. The main objectives of this study is to spot the issues of Hargeisa water system by assessing the current status of the water supply system in the town, evaluating the Hydraulic performance of the WSS and eventually propose remedial measures. The current status was evaluated rely on the difference in the supply and demand of the town by forecasting its population while the water losses was used the difference between the production and consumption data. Moreover, to investigate the existing water supply and distribution system, an EPANET software was used to develop the model. The model can be used to customize the high pressure and low pressure zones in junctions and the level of velocity through pipe. The model run was performed for average, maximum, peak and low demand situations to investigate the system model. The analysis result shows that the supplied water in the town is only covering 13.5% of the demand. Hence, this result indicates that there’s a high gap between the demand & supply. In Addition, from three years obtain data of production and consumption the average loss became 9.75%. Moreover, the result and discussion shows that there are totally different issues of the system like high pressures and low pressure whereas, the utmost pressure occurred at gravity main pipe line in night demand was 85.92m which is above the suggested value and also in the low hour demand (LHD), 100% of the velocity in the pipes is less than 0.5m/s. To handle the problems, it needs providing extra pumps to increase the production, rehabilitate the prevailing well sources, maximizing the capacity of distribution pipe line by putting new pipes
REPRODUCTIVE BIOLOGY AND FEEDINDG HABITS OF THE NILE TILAPIA OREOCHROMIS NILOTICUS (L. 1758) (PISCES: CICHLIDAE) IN DAMTE DAM, WOLAITA ZONE SOUTHERN ETHIOPIA
(HAWASSA UNIVERSITY, 2024-10) ERMIAS SHIRKO BIRBIRE
Reproduction, feeding and condition factor of O. niloticus were investigated in Damte Dam based on the samples collected from February, 2024 to September, 2024. A total of 584 fish samples were caught ranging from 10 cm to 33.9 cm TL and 32 g to 750 g TW for males and 9.7 cm to 33.9 cm TL and 32.1 g to 421 g TW for females. The aim of this study was to investigate reproduction and feeding habits of O. niloticus in Damte Dam, Ethiopia. The overall male to female sex ratio was significantly different from 1:1 (ꭓ2=4.281, p<0.05). Lm50 for males and females were 14.7 cm TL and 13.9 TL cm, respectively. GSI values ranged from 0.26 to 1.59 for males and 0.25 to 1.8 for females. The fish bred throughout the sampling period with intensive breeding months in May, June and July. The length weight relationship was found to be curvilinear (TW = 0.0105TL3.1988). ACF value of male was minimum values of 0.40 to maximum value of 2.99 with a mean of 0.933 ± 0.013 and females O. niloticus ACF was ranged from 0.75 to 2.77 with mean value of 1.39 ± 0.016. Detritus (94.61%, 34.53%), macrophytes (88.41%, 29.59%), phytoplankton (85.18%, 31.36%), insects (18.33%, 2.61%) and zooplankton (11.59%, 1.90%) were using frequency of occurrence and volumetric analyses respectively. In general, ACF and ripe gonad were inversely proportional, and compared to other studies. The fecundity of O. niloticus in Damte Dam was relatively low. There was no observable variation in the food items between dry and wet months, but notable ontogenetic variation was seen in the diet. O. niloticus under 15 cm TL should be protected to save the breeding fish from the risky fishing of locals. The study emphasizes the importance of raising public awareness about the value of using fisheries resources to improve local communities' living standards and research on Damte Dam conservation