Since the detailed variable condition calculating method of steam turbine is very difficult to be used in the actual calculation process

a simple method to construct variable condition model according to heat balance diagram of the unit was proposed. By employing this method

calculation model of constant flow and constant power variable condition for steam turbines were developed. Moreover

by taking a supercritical 660 MW unit as an example

this model was applied to calculate the values of typical parameters under different typical conditions

and comparison between the calculated values and designed valves indicates the deviation was small. Furthermore

the correcting curves of main steam pressure

main steam temperature

reheat steam temperature

reheater pressure drop and exhaust steam pressure on heat rate and power under VWO condition were also obtained. The difference between the calculated correcting curves and that provided by the manufacturer was small. It demonstrates that the accuracy of the above variable condition model is high and can meet requirements of engineering calculations.