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Abstract：When measuring the grounding impedance of grounding grid with sine wave current as excitation signal, due to the inevitable parallel co-linearity between voltage lines and current lines, the resulting mutual inductance will lead to the high measurement result of grounding impedance, and affect the safety performance evaluation of grounding grid. In order to solve this problem, a grounding impedance measurement method based on combined wave measurement to eliminate lead mutual inductance is proposed. The grounding impedance resistance component is measured with square wave current and the grounding impedance modulus is measured with sine wave current. The measured values of different mutual inductance coupling strength are obtained by changing the parallel col-linear distance at the measurement site. After the mutual inductance coupling component is analytically eliminated, accurate grounding impedance measurements can be obtained. Comparing the grounding grid measurement results at the 110kV substation site by angle method and reverse method with the simulation results based on layered soil model, the the error between the combined wave method measurement results and the simulation value of grounding impedance is only 1%.