Abstract: In this paper, a novel algorithm for protection of series compensated transmission line has been presented. Sending and receiving active power are calculated and used in the algorithm. There are many problems in protection of series compensated line such as voltage and current inversions. Therefore, in order to overcome the difficulties in protection of series compensated transmission line, in this paper a power differential protection algorithm has been proposed. Two restraint indices have been applied, if operating index be larger than each one the relay will issue the interrupt command. Each of the two criteria is not able to protect the line alone, but the combination of these criteria can protect the line properly. In some conditions, both criteria will issue trip command. The relay responses to the earlier command and this fact results in the hybrid algorithm becomes faster. All simulation results indicate correct operation in different fault and operation conditions. The proposed algorithm operates on each phase independently, thus the benefit of the single phase tripping is achievable.

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