When the AC system occurs breaker failure fault or dead zone fault in Ultra high voltage AC/DC hybrid system, the fault will be isolated after a long time, it can lead to commutation failures and blocking in DC transmission systems. In order to solve this problem, the fault isolating time components as well as the optimized links of breaker failure and dead zone protection in AC system by 3/2 connection are analyzed, and optimization techniques of breaker failure and dead zone protection is researched. It presents one kind of distributed fast failure and dead zone protection system by string integrated. By optimizing the logic of circuit breaker failure and dead zone protection, simplifying the circuit, shortening the transmission time of remote trip command and improving the logic of remote trip protection, reducing the redundant delay of multi-link, it can reduce the breaker failure and dead zone fault isolating time to less than 200 ms. Results of simulation and prototype experiment verify the effectiveness of the proposed theory and control strategy.