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DISTRIBUTION SYSTEM RELIABILITY ENHANCEMENT BY ASSET MANAGEMENT STRATEGIES FOR NETWORK RECONFIGURATION (ACASE STUDY OF NEKEMTE CITY DISTRIBUTION NETWORK
(Hawassa University, 2020-10-19) TADESSE GAROMA JAWI
Assets aging, corrosion, deterioration and slow replacement rate causes derating of the distribution
system reliability and frequently damage and burn for the assets. They cause system power outage in
radial distribution system in which a single power supplies the whole system. Thus, the objective of the
study is to enhance the distribution system reliability by asset management strategies for network
reconfiguration.
Nekemte city is located in western Ethiopia, Oromia Region, East Wollaga Zone at latitude 9°5′N, and
longitude of 36°33′E . Nekemte city distribution network is selected as a case study area in order to
collect and analysis asset management strategy (in appendix (A) and reliability data (Appendix (B). The
study is limited to circuit breakers (15Kv), transformers (15/0.4Kv) and OH lines (15Kv) assets. Age
and health condition data’s of assets are collected to evaluate each asset’s health index. Health index is
used to decide the proper maintenance and replacement strategy for present and future. As the result of
asset management strategy, two (2)circuit breakers, seventy seven(77) transformers and forty point one
(40.1) km of distribution overhead line requires replacement strategy and five (5) transformers and point
seven(0.7) Km of distribution overhead line requires preventive maintenances.
The placement and populations of automatic reclosers, sectionalizing switches and automation switches
are optimized using Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) for network
reconfiguration. Since, GA is better for local optima solution and PSO is better for Global Optima
solution, it is better if the results of both compared. In this thesis using PSO is better result than GA
result. GA and (PSO) are developed in MATLAB R2016a software as shown in Appendix (C) and
Appendix (D) respectively. PSO results five (5) sectionalizing switches, seven (7) Automations switches
and eighteen (18) reclosers and their respective position in distribution line. DIgSILENT Power Factory
15.1.7 software is used to demonstrate and simulate distribution system to assess reliability Index.
Using Asset management strategy for network reconfiguration the distribution system, SAIFI is improve
by 84.56 percentage from 87.2 to 13.461 per customer year, SAIDI is improved by 98.27 percentages
from 5889.86 to 101.565 hours per customer year. ENS improved by 98.24 percentages from 119.407
to 3.913MWh per year, and EIC improved by 98.24 percentages from 11.942 to 0.21 and save 11.732
M$ in a year. These work have Payback period of 1.742, therefore it is economically feasible if
implemented
POWER DISTRIBUTION SYSTEM LOSS MINIMIZATION AND VOLTAGE PROFILE IMPROVEMENT USING HARRIS HAWKS OPTIMIZATION TECHNIQUES (CASE STUDY: DEBRE BERHAN POWER DISTRIBUTION SYSTEM
(Hawassa University, 2021-10-12) SEID AHMED MUHYE
Growing concerns over environmental impacts, conditions for improvement of the whole
distribution network, shortage and expensiveness of fossil fuel, the deficiency in generating
capacities, and ever-increasing demand for electricity have set the way towards distributed
generation (DG) units in commercial and domestic electrical power systems. The major
problems of distribution systems, such as load growth, power outage, overloaded lines,
quality of supply, and reliability can be solved by optimally placing distributed gener ation near to the customer side. However, the non-optimal placement and size of DG
units may lead to high power losses and bad voltage profiles on the power network. This
thesis paper aims to minimize system real and reactive power losses, cost and improve the
voltage profile of the system by determining the optimal size and penetration of wind based distributed generation using Harris hawks optimization. The results of base case
load flow analysis showed that the case study distribution network feeder has a base case
active and reactive power loss of 1629.04KW and 609.513KVAr respectively. The feeder
minimum bus voltage and total voltage drop index at the base case is 0.8497V and 0.4407
respectively. The propossed HHO determines the optimal location and size of DG based
on minimum loss reduction index, voltage deviation index, and the cost of DG at the
same time to use the existing distribution network in an optimal manner. The optimal
location of DG is determined to be 33 and 38 with a size of 2.4997MW and 2.4896MW
respectively. The active and reactive power loss reduced to 290.097KW and 254KVAr
after the DG integration. The method is implemented and tested on the Sheno feeder of
the Debre Berhan power distribution system
A MICROGRID ENERGY MANAGEMENT SYSTEM IMPLEMENTSTION USING MIXED-INTEGER LINEAR PROGRAMMING
(Hawassa University, 2020-04-27) SINTAYEHU TERBUSH
The ever continued growth and development of distributed generation (DG) in the electrical grid
system led to the increasing expansion of microgrids across the world. Microgrid is distributed
power generation units, energy storage devices, and controllable loads with the capability to
operate in both grid-connected and island modes. Microgrid's economic operation is achieved
through an energy management system that optimally schedules distributed generations and
storage devices and continuously balances supply and demand. In this paper, a formulation of
optimal unit commitment and dispatch scheduling of DGs in a grid-connected microgrid is
presented. Mixed-integer linear programming (MILP) is used to carry out the optimal resource
scheduling model. The goal is to reduce the overall operating cost of the system by optimally
utilizing an energy storage device and a diesel generator unit by using load and renewable energy
generation prediction. Operational constraints such as generation limits of DGs, battery
charging/discharging limits, and state of charge (SOC) limits to be satisfied during all intervals
of operation. Simulation results indicate that the operational cost of the system is effectively
reduced through optimal scheduling of an energy storage system and a diesel Genset unit using
the proposed strategy
FEEDBACK LINEARIZED INDUCTION MOTOR CONTROL USING FOSMC AND SLIDING MODE-MRAS ESTIMATOR
(Hawassa University, 2020-10-13) YESHIWAS FETENE MENGESHA
The Model of induction motor indicates that it is nonlinear, MIMO and strongly
coupled system. To control this nonlinear motor as a nonlinear system, application
of IOFL and sliding mode controllers are promising. Application of sliding mode
controllers results the problem of chattering which is undesirable for electrical drive
system. Here, this problem is tackled by using sigmoid function instead of signum.
On the other hand, all states of squirrel cage induction motor are not easily accessible
and use of mechanical speed sensor increases cost of the drive system. The proposed
system eliminates the need of mechanical speed senor by employing combined Model
reference adaptive system (MRAS) and sliding mode estimation technique which is
known for robustness to model uncertainties and load disturbances. From simulation
results carried out it is also observed that by using proportional integral derivative,
sliding mode controller and fractional order sliding mode controller an overshoot of
9.5211%, 0.4753% and 0.3674% are found respectively for 120 rad/sec speed reference.
FOSMC shows best robustness for load torque disturbance having a minimum speed
drop of 1.1757% while PID and conventional integer order SMC have higher speed
drop of 5.5982% and 1.388% respectively at the instant 10 Nm is applied. Applica tion of sliding mode- model reference adaptive speed estimator gives good estimate
of rotor flux with mean absolute percentage error of 0.2584% and speed with mean
absolute percentage error of 0.1767%
INTERFERENCE ANALYSIS AND OPTIMIZATION ON 3G WCDMA NETWORK CASE OF HAWASSA CITY
(Hawassa University, 2021-01-12) Rahel Fekadu Zergawe
Hawassa is a city of tourism and education therefore city should have reliable and fast network
access. Currently Ethiotelecom’s serves as a service provider in the city with CDMA2000, 2G
GSM and 3G WCDMA wireless mobile network. 2G GSM and CDMA 2000 were the existing
wireless service networks, in the last five years, 3G WCDMA wireless service is added. As an
issue, there is still a lot of complain considering 3G WCDMA performance of network. We
consider the high interference value taken from the ethiotelecom network management system and
analyze problems, and solution for the problems is found by tuning Two main parameter of the
network CPICH power and Antenna electrical tilt using a heuristic algorithm to define the
optimum value for this specific case, The task is performed by measuring received total wideband
power (RTWP), Radio access bearer (RAB) and radio resource controller (RRC) key performance
indicator (KPI) values from the operation and maintenance center client system, then analysis is
done using WINPROP simulating tool, to compare the real network current configuration
parameter value with the parameter configuration that we suggested, using Ethiotelecom’s
suggested KPI value as a base line. From the analysis we concluded that using the two parameters
in combination enabled more improvements in both reductions of interference and network
capacity gain comparing with the tuning parameter individually. Accordingly, interference could
be minimized from −94.9𝑑𝐵𝑚 to −101.7𝑑𝐵𝑚 with network capacity gain of 4.04% fulfilling the
required Eb/No and received power threshold and using common pilot indicator channel(CPICH)
signal power of 7.5% of the total base transceiver station(BTS) power and electrical antenna down
tilt by 2 degrees. Using common pilot indicator channel (CPICH) power and antenna tilt setups,
the heuristic algorithm we use optimizes RTWP (uplink interference). The parameters chosen have
a considerable impact on network capacity. We use WINPROP, a static universal mobile
telecommunication system (UMTS) frequency division duplex (FDD) network simulator, to
evaluate the network settings