High speed protection scheme for EHV transmission lines

A new high speed distance protection scheme for single line to ground faults and multi phase faults for EHV (extra high voltage) transmission lines is described in this paper. This scheme also performs well on series compensated lines. The new complementary fast tripping algorithms together with the earlier experienced algorithm and multi-processor based distance algorithm, have led to the development to an adaptive hybrid scheme. This scheme is implemented into a well-proven hardware platform with moderate requirements on the communication. The protection scheme provides high speed tripping (less than one cycle) and high speed signalling. Extensive testing by using EMTP simulations as well as real time simulation with a power system simulator have confirmed the validity of this hybrid concept as a fast, secure and dependable protection scheme. The scheme is in operation in some 20 countries around the world.