Reliability evaluation of power supply system for power utilities' communication system in Japan

This paper presents an unavilability evaluation method of power supply systems for power utility telecommunications and evaluation results using field data. Telecommunication systems in a power utility system have a numerical target of unavailability to be satisfied because they play an important role in power system protection relaying. Recently, switching-type equipment and VRLA batteries have been widely used in Japanese telecommunication power supply systems. To evaluate the unavailability of these systems, the authors developed an evaluation method for a typical configuration of power supply systems and evaluated their unavailability using field data obtained from a questionnaire to 10 power utility companies. As a result of this evaluation, they found that several configurations of the system did not satisfy the unavailability target and changing configuration or parameters are needed. This method can be used not only to confirm the configuration is proper or not but also the case the value of parameters change such as time capacity of engine generators and batteries, inspection intervals etc.