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For many measurement cases of ground impedance of substation, the inductive coupling between the measuring lead wires is inevitable, which will greatly increase the measurement errors. There is no effective method to solve this problem till now. A new method to accurately measure the ground impedance in strong inductive coupling conditions is proposed. The proposed method can measure the ground impedance and the mutual impedance between the measuring lead wires by solving a set of equations composed by the measured voltages and currents. A measuring instrument based on industrial computer is developed. Digital simulation experiments are carried out on real-time digital simulator (RTDS). A field measurement case of 500-kV Yanshan substation is given. Both the RTDS simulation and the field measurement validate that the proposed method and the developed measuring instrument can measure the ground impedance and the mutual impedance precisely. [ABSTRACT FROM AUTHOR]