Extra high speed hybrid protection scheme for high voltage transmission line

To improve the reliability of traveling wave protection, this paper proposes a hybrid protection scheme based on the traveling wave polarity comparison principle and current differential principle. In this scheme, the traveling wave relay is primary and the current differential relay is supplementary. Two complementary relays simultaneously operate to ensure that the hybrid protection has a good performance. For the general faults, the traveling wave relay can fast discriminate internal faults from external faults using the polarity characteristics of initial current traveling wave. For some special fault conditions, the identification result for fault is determined by the current differential relay. Therefore, the sensitivity and reliability of traditional traveling wave protection may be greatly improved. Using the same hardware platform and only requiring current signal, the hybrid scheme is easily achieved. Simulation results verify that the hybrid protection has fast speed and high reliability level.