DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING
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Item Reliability and quality assurance of electronic component(Duncan Science Company, 2010) Ajenikoko, G. A.||||Raji, T. I.; Fakolujo, O. A.; Raji, T. I.An electronic component is an entity in a system which can not be further sub divided in the course of a given relability. However a component can make up parts which is regarded as self-contained unit. Thus while thereliability of a system can be influenced by altering its structure, the reliability of what is considered a component cannot be changed in such a manner, and if different characteristics are desired, the component must be replaced by another with different reliability parameters. Electronic components can be classified into two groups. The first group are those that are observed only until they fail, because either they cannot repaired, or the repair is uneconomical, or the problem is such that only the life history up to the first failure is of interest. These called non-reparable (or non-repaired) and their failures are catastrophic. The second group are those components that are repaired upon failure, hence their life histories consist of alternating operating and repair periods. They are called repairable components. This paper presents the basic concept of electronic component reliability and quality assurance. A brief historical perspective is presented along with operational definitions. The factors affecting reliability as well as the costs to provide reliability re also described. Failure modes are depicted as well as the environmental effects that affects reliability.Item A generalized model for quantitative evaluation of reliability indices of the national grid system(2010) Ajenikoko, G. A.; Fakolujo, O. A.|; Raji, T. I.Reliability indices are considered to be reasonable and logic ways to judge the performance of an electric power system. Reliability indices which are proposed by the IEEE are used to evaluate the performance of selected distribution systems on the national grid. Ten years of outage data (1998 - 2007) from seven selected distribution systems on the national grid were used as case studies in this research work. A generalized model is developed for a quantitative evaluation of relative indices of the national grid system. The development of the model stated with identification of the system reliability indices and estimating the contributions of system indices to the failure rate of the selected distribution system on the national grid. The computed system reliability indices are used as input parameters for the generalized model. Relative CAIDI index is computed by simulation using MATLAB 7.7 which automatically generates the graph of the relative CAIDl against names of feeders. The percentage average relative CAIDls for Ibadan, Port-Harcourt and Benin distribution systems are 71.86%, 52.79% and 75.79% respectively, thus, average reliability levels. Ilorin, Ikeja, Kaduna and Kano distribution systems have percentage average relative CAIDls of 11.95%, 39.76%, 40.17% and 41.08% respectively with poor reliability levels. With the aid of curve fitting (cf) tools, two distinct model equations were developed from which a generalized model is formulated for a quantitative evaluation of reliability indices of the national grid. The generalized model is a polynomial function whose order depends majorly on the level of industrialization of the distribution systems and the number of distribution feeders.Item A modified linear contribution factor model for improvement of relability indices of electrical distribution systems.(2009) Ajenikoko, G. A.; Fakolujo, O. A.; Raji, T. I.In Nigeria, satisfactory degree of reliability has not been attained in our power systems in recent times. The average duration of interruptions that customers experience is quite high and the degree varies from place to place. This is evident all around the nation, most especially in urban commercial cities. Previous researchers have focused on assessment of power system reliability indices using different models. In this work, a computationally efficient 'modified linear contribution factor model (LCFM) is developed. The model can be used for appreciable improvement of all the major system reliability indices of practical distribution systems unlike the conventional LCF model which can only improve some of the system reliability indices of practical distribution systems. Data collection and data analysis were carried out to develop the LCF model used on the three selected distribution systems on the Nigerian National Grid. The results 'of this work indicates that part of the reliability indices computed for the distribution systems SAIFI is more sensitive to the LCF model than SAIDI and CAIDI but that the sensitivity is low for SAIDI index compared to CAIDI. This is due to the quantization of the annual number of customer interruptions caused by the type and placement of protective devices on the distribution systems of the National Grid. With the use of the modified LCF model, the average percentage improvement in the system reliability indices become 97.72%. 98.55% and 98.63% for Ibadan, Ilorin and Ikeja distribution systems respectively as against an average percentage improvement of 36.08%. 11.36% and 24.36% in the system reliability indices for Ibadan, Ilorin and Ikeja distribution systems respectively with the use of conventional LCF model. The result of this research work confirms the efficiency of the modified LCF model.Item A generalized model for quantitative evaluation of reliability indices, of the national grid system(2010) Ajenikoko, G. A.; Fakolujo, O. A.; Raji, T. I.Reliability indices are considered to be reasonable and logic ways to judge the performance of an electric power system. Reliability indices which are proposed by the IEEE are used to evaluate the performance of selected distribution systems on the national grid. Ten years of outage data (1998 - 2007) from seven selected distribution systems on the national grid were used as case studies in this research work. A generalized model is developed for a quantitative evaluation of relative indices of the national grid system. The development of the model stated with identification of the system reliability indices and estimating the contributions of system indices to the failure rate of the selected distribution system on the national grid. The computed system reliability indices are used as input parameters for the generalized model. Relative CAIDI index is computed by simulation using MATLAB 7.7 which automatically generates the graph of the relative CAIDl against names of feeders. The percentage average relative CAIDls for Ibadan, Port-Harcourt and Benin distribution systems are 71.86%, 52.79% and 75.79% respectively, thus, average reliability levels. Ilorin, Ikeja, Kaduna and Kano distribution systems have percentage average relative CAIDls of 11.95%, 39.76%, 40.17% and 41.08% respectively with poor reliability levels. With the aid of curve fitting (cf) tools, two distinct model equations were developed from which a generalized model is formulated for a quantitative evaluation of reliability indices of the national grid. The generalized model is a polynomial function whose order depends majorly on the level of industrialization of the distribution systems and the number of distribution feeders.