Removal of decaying dc in fault current signal

Hello everybody,

How can I remove the decaying dc from fault current signal? When any fault occurs on transmission line, the fault current contain decaying dc along with harmonics. But for the exact phasor estimation, the decaying dc must be removed from the fault current signal. I also tried 'DC blocker' from DSP system toolbox, but in that, I am not familiar with normalized frequency, type of FIR, IIR or mean subtranction algorithm, so what should be their exact values that I can't decide.

I have attached its waveform and its magnitude. Due to decaying dc, the magnitude of fault current stops fluctuating after 3 or 4 cycles of fault initiation. I want to remove this fluctuation just after the fault initiation by removing decaying dc from the fault current signal.

Please, suggest any matlab code or any simulink model for that.