Line commutated converter based high voltage transmission line suffers from converter faults where the converter experiences commutation failure of the device. This fault occurs when the ac voltage drops or the short circuit occurs and is more frequent in the inverter. The fast detection of a fault is essential because improper transferring of current from one device to another can cause stress on the device and interruption of transmitted power. In this paper, a fast scheme for protection against commutation failure due to decrease or faults in ac voltage is implemented using a fuzzy logic controller. The rectifier end data voltage and current signals are chosen as an input to detect the faults. This scheme has good selectivity, reliability, accuracy and robustness.