This thesis presents a general-purpose power quality assessment at selected industries inrnthe city of Addis Ababa. From the point of view of its academia purpose, the assessmentrninvestigates all the major transient and steady state electrical phenomena that disturb thernpower quality of a conventional power system. As such, the seven major categories ofrnpower quality phenomena listed by the IEEE Standard 1159-1995 are assessed in thisrnthesis work.rnThe necessary data are collected from recorded data of the Ethiopian Electric PowerrnCorporation and plants of study, from phenomena record of utility eqiupments, andrnthrough direct measurement using harmonic analyzer. The time schedule of datarncollection and measurements, as to meet the IEEE requirements, varies from a singlernpower-period to 11- years depending on the power quality event to be studied. From thernground of the objective of the assessment, the monitoring locations on the other hand arernchosen to be the service entrances of the corresponding industries.rnThe collected data are analyzed and the results are then compared with the IEEErnrequirements. In that case, voltage variations reaching 21% and frequency deviations ofrn1% to 4% are discovered. Current distortions of THD value that reach 33.5% are alsorndiscovered at Wubcon plc. Harmonic filters, that have an added feature of power factorrncorrection, are therefore designed for Wubcon plc.rnSoftware simulations are run using SimPowerSystems, Simulink to show the level ofrnmitigation of the proposed solutions for capacitor-switching transients. The designedrnfilters for Wubcon plc are also run on SimPowerSystems.rnKey words: Power quality, Power quality phenomena, IEEE standards, Reliabilityrnindices, Benchmarking metrics