Abstract: A method for inter-turn fault detection in a current transformer (CT). The method includes obtaining a first inter-turn fault index of the CT, obtaining a second inter-turn fault index of the CT, and detecting an inter-turn fault in the CT based on the first inter-turn fault index and the second inter-turn fault index. Obtaining the first inter-turn fault index includes coupling an AC power supply to a secondary winding of the CT, measuring an electric current passing through the AC power supply, obtaining a hysteresis curve of the CT from the electric current, and calculating the first inter-turn fault index according to the hysteresis curve. Obtaining the second inter-turn fault index includes injecting an AC current to a primary winding of the CT, measuring an open-circuit voltage waveform of the secondary winding, and calculating the second inter-turn fault index according to the open-circuit voltage waveform.