This paper proposes a novel scheme to detect the
saturation of current transformers (CTs) for protection blocking.
The scheme modifies the morphological skeleton method and
applies it to analyze the shape information of CT secondary
current. Afterwards, two indices are introduced to determine
the existence of saturation. Simulation studies under a variety of
fault conditions have been conducted using PSCAD/EMTDC to
evaluate the performance of the proposed scheme. The results
have shown that the proposed scheme is able to detect CT
saturation accurately, and is robust to noise and sensitive to mild
saturation.