For transmission and distribution lines, cross-linked polyethylene (XLPE) cable plays an important role in distributing the stable power to customers. Electric failure for the XLPE cable decreases year by year because of progress of manufacturing. However, at joint and terminal sections of the XLPE cable, partial discharges (PDs) occur in defects of insulating materials. The PD is a precursor to dielectric breakdown. Once PD occurs, it continuously erodes insulation material. The demand of reliable power systems is quite crucial for all of power companies, and then it is demanded to develop an on-line PD measurement technique and a monitoring system. In this study, we propose a PD locating system for XLPE cables in operation, in which the propagation velocity of PD current is not required for locating a PD. We first show how the locating system works on a XLPE cable network with time synchronization between two points. Additionally, the locating accuracy of the system is investigated.