ABSTRACT
This work presents the reliability assessment of the Power sub-system of the North West Region of Airtel network for a period of one year. The Power model was found to be an integrated setup of major Power subcomponents such as transformer, automatic voltage regulator, generators, rectifier system, battery bank, and Power control systems such as automatic transfer switch and automatic main failure, which are all interfaced in a definite topological structure, with unique redundancy model at each network site.The impact of critical power failure event at different hierarchical stations on the subscribers was also assessed. The reliability data for power sub-system was collected to determine the reliability indices of the power equipment. The data were analysed using the MATLAB version 7.4 software. The two-generator system at the integrated switch sites, integrated hub sites, terminal end sites and independent of PHCN powe supply on the network exhibited relatively high reliability with fault tolerance by the prevalence of duty cycle availability indices of 51.83%, 56.00% and 56.5% respectively under a standard configuration of 50.00% duty cycle absolute availability index for a generator unit. The rectifier system with modules of failure rate of 0.040/103h installed on the network was deduced to possess a high reliability index close to unity within a unit hour interval. Empirical findings show that the use of battery units with voltage rating of 3V, 6V and 12V on the network of -48V combinatorial battery bank system would yield relatively high reliability close to unity. The study result showed that the efficiency of the network power system model depends on the degree of automation of the subcomponents and the degree of ambient condition changes. It was concluded that the reliability standards of the GSM power sub-system are dynamic and depends on the redundancy mode of each subcomponents, the degree of redundancy, the failure ratings or lifecycle and scalability of the subcomponents unit used in the system under optimal working conditions of all the subsystems and ideal maintenance practice.