Abstract: In energyloss analysis of thermal power units, the vacuum base value usually obtained by fitting the curve of condenser characteristics provided by the condenser manufacturer, and this is suitable for special condition only, in which the cooling water flow, the condenser steam flow, the cooling water flow velocity, the cooling water temperature at the inlet and other parameters are all in the range of designed value. Taking the 150MW unit of Inner Mongolia Huadian Wuda Thermal Power Company Limited as example, the vacuum base values obtained by three calculation methods were analyzed and compared. The result shows that according to the base value obtained by fitting the manufacturerprovided condenser characteristics curve, it is can not calculate the condenser pressure base value, and the calculated value obtained under variable working condition of the condenser should be taken as the vacuum base value.

Key words: energy-loss analysis, base value, variable working condition of condenser, vacuum degree