Discrete Fréchet distance algorithm based criterion of transformer differential protection with the immunity to saturation of current transformer

Abstract The saturation of current transformers (CTs) has adverse impact on the reliability of the transformer differential protection. However, the overall phase information of currents are less affected by CT saturations. The Frechet distance algorithm, which is provided with the superiorities in the similarity identification, is utilized to acquire the phase information difference between the currents on both sides of the transformer. On this basis, the discrete Frechet distance algorithm based criterion of transformer differential protection is put forward. It can identify the differences of phase characteristics of currents on transformer both sides under various conditions including faults accompanied with CT saturations, transformer ultra-saturation and abnormal samplings. The effectiveness of the proposed criterion were validated respectively with simulation and experiment tests.