Which term refers to the probability of a system or component performing required tasks?

The term that refers to the probability of a system or component performing required tasks is reliability. Reliability specifically focuses on the consistent performance of a system over time under specified conditions. It is a measure of how likely it is that a system will function correctly without failure during its intended operation.

In the context of power substations, reliability is crucial as it impacts the continuity and stability of power supply. If a substation or its components are deemed reliable, it means they can be expected to perform their intended functions effectively over their operational lifespan, which is vital for maintaining service quality and safety.

While efficiency refers to the optimal use of resources to achieve a task, and effectiveness is about achieving desired outcomes or objectives, these concepts do not specifically measure the likelihood of consistent performance over time. Durability speaks to the endurance or lifespan of a component under stress but does not directly address the probability of performance. Thus, reliability is the most appropriate term in this context.