Reserve Margin
supply reserve margin · installed reserve margin · operating reserve · 예비율
The reserve margin is the spare supply (reserve) secured above electricity demand, expressed as a ratio to demand. It shows the safety buffer against generator failures or sudden jumps in demand.
The rules define 'reserve' as spare capacity that can raise or lower supply or demand to keep the system balanced. Within it, supply reserve is supply capability secured above demand. The reserve margin is this buffer expressed as a ratio to demand.
Two kinds of reserve margin are used in Korea. One is the installed reserve margin, which compares the whole fleet with peak demand and is used in long-term planning and in capacity payment calculations (the rules' 'market reference reserve margin'). The other is the supply reserve and supply reserve margin, which look at the supply capability actually available on the day. KPX sets operating reserve standards, manages them in real time, and takes staged measures when a shortfall is expected.
News-reading tip: when a summer or winter story says the 'reserve margin is falling', first check whether it is on an installed basis or a same-day supply basis. Also note that reserve is stated in MW and the reserve margin as a ratio.