I have year by year data of number of faults in 330 kV power transformers. Faults are of various kinds and there is no additional information about how many of those faults led to power outage. I am mathematician and just have basic knowledge in power engineering. I understand that not all faults in the transformer will lead to power outage in lines connected to those transformers. But is there a conservative bound for power outage probability? For example, approximately 16 % of all faults leads to power outage. I assume it is a very long shot, but maybe someone might have some suggestions

No power outage, will be with, any opened circuit fault, generally, from short circuit fault(fault with power outage), fault is made open circuit by auto re closing the circuit(fault current (burn) clear fault), and will be removed, if exist, generally more than 80% fault can be made open circuit by auto re closing. Some times, the transients (like inrush) in system may gives falls tripping, and the needed auto re closing can be avoided by fast acting computer based relaying(wave form approached). Auto re closing can also minimized (life consuming cost can be minimized of power equiepments) for transients and temparory faults, by micro controller based relay design for specific function....can refer my papers(web B.T.Desai).

May be any frictional or rotating fault in tapchangers or any stray magnetic field loss will contribute very little or have no significant effect on power outage.