Power cable is an important component of urban transmission and distribution systems, and its insulation status is related to the reliability of urban power supply. Partial discharge detection is an effective method to identify potential insulation faults and can be used for insulation diagnosis of power cables. Transient earth voltage (TEV) is a non-electrical contact and flexible application of partial discharge charging detection, which can effectively detect partial discharge of cable terminals or joints. However, due to the wide distribution of cable attachment monitoring points, strong timeliness requirements and large electromagnetic environment differences, the current TEV live detection application methods have certain limitations. In this paper, the time-frequency characteristics of the internal discharge signals at the cable terminations and joints are analyzed. The capacitive TEV sensing unit and signal pre-processing circuit capable of effectively coupling the transient-to-ground voltage are designed and based on the TEV wireless sensing unit. A distributed TEV wireless sensor network was established. In this paper, the coupling principle, signal conditioning and acquisition, and data processing methods of transient ground signal are studied. Through the sensing quantity, trend and pattern recognition of each sensor node, the associated fault early warning is realized.