Abstract: When a short circuit fault occurs in the substation grounding grid,the current on the conductor and the leakage current in the soil will generate a strong spatial magnetic field,which may affect the normal operation of the equipment in the station and endanger the safe operation of the substation. The existing method cannot detect the leakage in the soil. The effect of current on the magnetic field. In this paper,a flexible broadband antenna with ultra-thin liquid crystal polymer LCP as the dielectric substrate is designed to accurately detect the spatial magnetic field of the substation grounding grid. The basic radiating element of the antenna is a broadband monopole antenna,which adopts micro Feeding mode with feed. The software simulation results show that the antenna covers the working frequency range of 0.5 KHz -22 KHz,which has met the requirements of broadband antenna.