Power System Availability Performance vs Overall Cost

The power systems in a time division telecommunication network fall into two categories. The great number of small power equipment feeding concentrators constitute the mainn bulk of maintenance cost and should therefore be optimized for a minimum life cycle cost. The power systems of central switching stations should be designed for maximum availability performance because of the extremely severe effects of power outage. To satisfy the need of quantitative availability performance data, an analysis method is presented, which gives the mean time between system failures and mean down time as a function of the reliability and maintainability performances of power system components and the maintenance support performance. The analysis reveals that the dominant path to system failure will be via dormant faults in batteries, stand-by units or alarm and signalling circuits. This result is confirmed by field data, almost every system failure was an outcome of lacking alarm information. The most dominant rectifier failure cause in rural areas was the lightning originated surge voltage, which also influences the choice of system configuration.