An algorithm for longitudinal differential protection of transmission lines

- Algorithm is completely insensitive to current transformer saturation.
- Prompt response during faults within the protected zone.
- Minimal amount of mathematical operations.

This paper describes a new algorithm for longitudinal differential protection of transmission lines. Classic stabilization is an unreliable method for avoiding unnecessary relay tripping in case of current transformer saturation during faults outside the protected zone. There are various methods for detecting current transformer saturation. The paper's thesis is that rather than the stabilization current, the direction of the currents introduced into the relay should be monitored. The proposed algorithm has been compared to the algorithms used by renowned relay producers. Different types of faults have been simulated, both within and outside of the protected zone, and the paper demonstrates how the relay trips when the algorithm in question is used. The results have proven that current transformer saturation does not affect protection operation, and that a prompt relay response is obtained for faults occurring within the protected zone.