Some Insights Into the Effect of Maintenance Quality for a Protection System

This paper considers an inspection and preventive replacement policy for a one-component protection or cold standby system. Inspection is imperfect, and subject to false positives and negatives; preventive replacement may also be of poor quality. We determine conditions relating to the quality of the inspection and preventive replacement under which a maintained system would not benefit from the execution of inspections and preventive maintenance. We present examples with decreasing failure rate component lifetimes in which preventive replacement is cost-optimal, contrary to the classic policy. Such cases arise when inspections do not necessarily detect the failed state.