Fig. 1. Configuration of direct-current fiber-optic current transformer (DC FOCT)

Fig. 2. Dynamic model of DC FOCT

Fig. 3. Frequency response characteristics of closed-loop signal-processing system. (a) Amplitude-frequency characteristic; (b) phase-frequency characteristic

Fig. 4. Frequency response characteristics of digital output filter. (a) Amplitude-frequency characteristic; (b) phase-frequency characteristic

Fig. 5. Frequency response characteristics of DC FOCT. (a) Amplitude-frequency characteristic; (b) phase-frequency characteristic

Fig. 6. Test platform for harmonic current measurement accuracy of DC FOCT

Fig. 7. Measurement results of harmonic current measurement error of DC FOCT (insert: local amplification of error curves)