Interruptions which are largely unavoidable contribute to the unavailability of power and the inability of the power system meeting the electricity demands of the consumers. The incessant interruptions and unstable power supply from the grid could be as a result of unreliable nature of the distribution system, which is unhealthy to the consumers, power system equipment and the utility company. Therefore, to minimize this unreliability issues, the power system planners need comes up with an upgrading approach with a view of improving the reliability of the distribution system. In this paper, reliability assessment of Okwuzi, Omoku 11kV distribution system was carried out using one year (January to December,2023) outage frequency and duration data gotten from the utility, in order to ascertain the reliability performance of the system by determining key reliability indices, and proposes penetration of distributed generation if the indices fail the set standard. Electrical Transient Analyzer Program (ETAP) software was used for the simulation. This was done by carrying out reliability study of the existing 11kV distribution network using embedded analytical equations in ETAP; reliability indices were determined, and improved upon by the penetration of PSO optimized distributed generation (1.63MVA) in bus 9 and reliability study was performed with DG. The results obtained indicate that when DG was injected into the system, average failure rate and average outage duration at load point 6, reduces by 34.2% and 23.8% respectively, then, so on up to load point 14. Similarly, at the penetration of DG, there were significant improvement in the customer’s-oriented reliability indices; SAIFI, 0.4747 to 0.2535f/yr, SAIDI, 13.56 to 8.2585hr/yr, CAIDI, 32.577 to 28. 581hr.intr and EENS, 56.216 to 43.376MWhr/yr. The availability index ASAI improved from 86.8 % to 99.85% which is close to the 99.9989% IEEE benchmark