The ground system is vital in high-voltage substations and power plants to protect humans and equipment against lightning strikes and transient faults. Existing commercial devices cannot measure the earth system’s impedance at high frequencies with appropriate accuracy. Consequently, it is essential to have a tool that can measure the ground system’s impedance over a broad frequency range. In the implemented devices, an arrangement based on power electronics converters has been constructed to inject high-frequency voltage and current waveforms and measuring circuits to determine the harmonics of such waveforms. This device can generate a broad range of voltage and current, ranging from 0 to 300 volts and 0 to 5 amps, proportionate to the system impedance. Additionally, the impedance of the ground system is measured using a comprehensive control algorithm in two general steps. In the first step, the impedance value of the earth system is estimated. Then the reference voltage value is determined. The second step involves injecting high-frequency pulses into the ground system that are proportionate to the reference voltage value and the harmonics measured with high accuracy. Furthermore, differential probe circuits have been made separately to measure high-frequency voltage and current to enhance the accuracy of measurements.