-Korea has introduced power trading system since 2001 but long-term Generation system planning has been executed by government for cost minimization every 2 years. Until currently the model which is used for generation system planning and best-mix only considers cost minimization and total yearly or quarterly electricity demand every year. In a view point of one day power supply operation, the ramp up/down rate of total generation system, minimum up/down time and GFRQ(Governor Free Response Quantity) are very important. This paper analyzes optimal fuel-mix for 2022 Korea generation system satisfying these constraints of each fuel type and considering pump storage plants, construction cost and CO 2 Charge Using MILP(Mixed Integer Linear Programming) method. Also the sensitivity analysis which follows in future power industry environmental change accomplished.

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-As the increasing HIF(High Impedance Fault) with the arc cannot be easily detected for the low fault current magnitude compared to actual load in distribution line. However, the arcing current shows that the magnitude varies with time and the signal is asymmetric. In addition, discontinuous changes occur at starting point of arc. Considering these characteristics, wavelet transformation of actual current data shows difference between before and after the fault. Althogh raw data(detail coefficient) of wavelet transform may not be directly applied to HIF detection logic in a device, there are several developing methods of HIF monitoring data using the original wavelet coefficients.In this paper, a simple and effective developing methods of HIF monitoring data were analized by using the signal data through an actual HIF experiment to apply them to economic devices. The methods using the sumation of the wavelet coefficient squares in one cycle of the fundamental frequency as the energies of the wavelet coefficeits and the sumation of the absolute values were compared. Besides, the improved method which less occupies H/W resouces and can be applied to field detection devices was proposed. and also Verification of this HIF detection method through field test on distribution system in KEPCO power testing center was performed.

-This paper presents the result of the estimation of the power interruption costs of Korean commercial customers. Commercial customers are usually located in urban areas and considered very important because a power interruption on them can expand to additional damage to related users. Their power interruption costs were calculated through a survey with the process of data selection. Also, the power interruption cost for each customer's business type was calculated and compared with that of foreign cases.

KEPCO has adopted radial system at low voltage distribution. Recently KEPCO began to have the problems. As low voltage customer's limit was changed from 499 kW to 999 kW, the uses of large capacity transformer are increased. Installation space of TR & CB are insufficient at downtown area. Utility rate of transformer is low. When transformer is replaced, LV system experiences interruption. So we developed the underground low voltage loop system. KEPCO's LV loop system is consisted of HV CB, TR, LV loop IED, LV CB, operation system (server). To develop the low voltage loop system, we simulated the load flow and fault analysis by EMTDC program, made a simulator for lab test, developed the protection coordination and established test bed at 22.9kV network. And field test was done.