The ground wire is usually eliminated to reduce the order of the parameter matrix because of its direct connection to towers. However, the tower must be insulated from ground wires in the process of de-icing. In this paper, on the basis of analysis of multi-conductor system electromagnetic transient coupling in the case of insulated ground wires, the decoupling method of double-circuit electromagnetic coupling with asymmetric phases is deduced. A phase-mode transform matrix for an insulated ground wire is obtained. In addition, the insulated ground wire causing ‘speed increase in zero mode’ with the traditional decoupling matrix is pointed out. Based on the analysis, in consideration of the transient frequency response of capacitive voltage transformers, an indirect fault location scheme using fault locators in three-phase transmission lines to locate ground wire faults is proposed for a double-terminal fault location without synchronization. The progressive kurtosis curve is applied to remove the electromagnetic noise of real measured signals and the wavefronts are identified accurately. A large quantity of simulations is carried out to verify the effectiveness of the proposed fault location scheme.