Korean wide-area monitoring system for maintaining real time voltage stability of metropolitan region in Korea using PMU measurements

The Korean power grid can be characterized as follows: First, the metropolitan region which has more than 40% of total load demand and only 20% of total generation capability inherently requires a large volume of power transfer from other regions. And most generating units with low generation cost are in non-metropolitan areas. With the aim of economic operation, generators in the non-metropolitan region mainly take charge of the base load and then generators in the metropolitan region is operated to meet the demand increase in peak time. This also makes power transfer increase toward the metropolitan region. Therefore, these interface lines, six routs (765 kV and 345 kV), from the non-metropolitan regions to the metropolitan region are heavily loaded. Moreover, transfer limit needs to be constrained by voltage stability limit to operate the system in a secured manner considering severe outages. However, the trend of heavy power transfer will continue and become more and more profound because the construction of new facilities is difficult due to environment and the strong public opposition in the metropolitan region In this paper, a preliminary work of installing Korean Wide Area Monitoring System (K-WAMS) is introduced. The architecture of developed K-WAMS comprises of the following hardware components: • i-PIU(Intelligent Power system Information Unit) and Simulator • CSU&FEP Communication links • i-PIC(Intelligent Power system Information Concentrator) • i-PIS(Intelligent Power system Information System) The eight i-PIUs will be placed at major substations and generating units to allow observation of the Korean Power Grid transmission system under any operational conditions. The measured data will be transferred via dedicated communication channels, CSU and FEP, to a K-WAMS Monitoring and Assessment Centre of NCC level through open platform i-PIC, Data Management Centre of RCC level. A main purpose of this installation is to monitor dynamic voltage stability in metropolitan region. A real time index named WAVI (Wide Area Voltage stability Index) is used for the dynamic voltage stability indices to give an indication of how far away the system in from voltage instability. The preliminary study shows that it successfully predicts voltage instability through the comparative study using the conventional PV margins. In order to do time-domain simulation and voltage stability assess, off-line stability assessment tools are used.