It is very obvious that the development of every nation largely depends on availability of power supply. Users of electricity desire to have full confidence in the system for domestic and industrial activities to thrive. System Average Interruption Duration Index, System Average Interruption Frequency Index and Customer Average Interruption Duration Index were chosen to assess power system reliability in attempt to build greater customer confidence. In doing this, Greater Port Harcourt 33kV feeder at Rumuosi Transmission Station feeding Port Harcourt International Airport was considered for the reliability assessment. The results of reliability assessment on System average interruption duration index for the months of January, February and March, 2023 are 73.47hrs, 65.71hrs and 67.59hrs. Results of reliability assessment on System average interruption frequency index for the months of January, February and March, 2023 are 23.88, 21.24 and 21.94 interruptions per customer respectively while results on customer average interruption duration index for the months of January, February and March, 2023 are 3.08hrs, 3.09hrs and 3.08hrs. Each customer on the average lost power supply for about 3.08hrs in the month of January, 2023 representing 0.41% but having power supply for about 23.59hrs per day representing 99.59%. In February, customers were denied power supply for about 3.09hrs representing 0.46% but having power supply for about 23.54hrs per day representing 99.54% while for March, customers were denied power supply for about 3.08hrs representing 0.41% but having power supply for about 23.59hrs per day representing 99.59%. The values realized for the customer average interruption duration index for the various months under study point to minimal system failure, minimal fault occurrence in the different electricity distribution networks and quick response to clearing of fault(s). This indicates sufficiency in the power system with respect to demand and therefore, validates the reliability of the system because consistency test was sustained.