Power grid main characteristics
In South Korea, power transmission voltages are 765kV, 345kV on major network and 154kV in local systems. As of 2012, the total length of transmission lines was 31,662 Circuit-km (C-km) and the total capacity of substation facilities has been expanded to 27,1247MVA. There are three main characteristic in Korean grid as follows:
The power system in Korea consisted of the independent system like island. Furthermore, the metropolitan areas in central parts of Korea have consumed nearly 42 percentages of the total electricity generated. Multiple connections were established to supply a relatively large quantity of power flows northward for the metropolitan areas.
Korea’s transmission lines have been expended and improved rapidly, complying with the requests of customers to follow the improvements in the level of life style and industrial development. Therefore, 765kV facilities are now being constructed, to be operated, to transmit electricity stably between east and west large power generation plants and consumption areas.
There is two submarine transmission lines of HVDC (High Voltage Direct Current) cable between jeju island, which is located 100km apart, and main grid.
Major incidents & preventive measures
9.15 Rolling Black-out
On September 15th 2011, the last step (Emergency rolling outage) was implemented to prevent whole system black-out because of power shortage. It last about 4 hour 45minute, 15:11~19:56 and the amount of cut off load was 4,008MW. The cause of emergency was analyzed followings. The first reason was considered a failure of demand forecasting. It was 3,280MW the error between expectation and real from 64,000MW to 67,280MW. It is very difficult due to the extreme weather change and considering special holiday load pattern. Secondly, the available supply capacity was underestimated. There was miscalculation due to output decrease from temperature effects and water shortage in upper reservoir.
Since that incident, KPX holds the 7.50 meeting at 7:50 A.M daily to make system plan adequate and power system operational issue. To improve the accuracy of demand forecasting, though new load forecasting program development which minimizes the forecasting error was launched and the expert of meteorology was recruited. The standard of reserve power was also reinforced; national holidays could secure additional operating reserve. The communication strategy in emergency situation was reviewed coordinated with new emergency action plan. The calculation of available power considering the external parameter was tuned by improvement of EMS system.