Through the development of phasor measurement units (PMU), various aspects of power system dynamic behavior could be monitored and diagnosed. Monitoring dynamic voltage stability becomes one of achievements we can obtain from PMUs. It is very important to select the method appropriate to the KEPCO system since there are many voltage stability indices. In the paper, we propose an advanced WAVI (Wide Area Voltage Stability) for monitoring dynamic voltage stability. It reflects the PMU installation plan of KEPCO, thus it is suitable for KEPCO system specially. The salient features of the proposed index are; i) it uses only PMU measurements without coupling with EMS data, ii) it is computationally unburden so that it can be applied to real-time situation. The proposed index is applied to the KEPCO test system and the result shows that it successfully predicts voltage instability through the comparative studies.