Abstract: To address the issue of confusion between CT open-circuit faults and ground faults under low-current conditions, this study proposes a dual dynamic lockout method for low-current CT open-circuit detection based on temporal entropy and energy ratio: temporal entropy is used to quantify time-domain disorder, while the energy ratio distinguishes differences in spectral attenuation, and these are combined with the zero-sequence rms value to construct a collaborative lockout logic. Experiments show that, at currents ranging from 1% to 5% of the rated current, the discrimination success rate exceeds 90% and the response time is less than 100 ms, effectively improving the reliability and noise immunity of CT open-circuit detection in low-current scenarios.