Three types of voltage source are used in the measurement. The underground cable as rated 3.6/6 (7.2) kV with simulated defect was investigated. The inception voltage, electric charge, PD pattern, and PD location were investigated by using HFCT sensor and oscilloscope. The measurements results show the severities of termination defect. The TDR technique was applied to localize the PD location in simulated cable. In the conclusion, the defects during cable installation can cause the fast degradation of cable termination because of high electric stress and partial discharge initiation. Therefore, the life extension of underground cable system can be achieved by the good understanding and awareness of the problem.