Connecting with actual example of the heat-supply transformation of 4X210 MW unit in a certain power plant of Shanxi Province, this paper introduces the key technical points of the transformation of 200 MW straight condensing unit into heat-supply unit, providing the reference for similar transformation.

The discussion of the alteration from condensing power plant to cogeneration unit;

Transforming pure condensing steam unit into central heating one at low vacuum with circulating water can increase greatly the utilization ratio of thermal energy and reduce the lose of cold resources,producing obvious economic and social benefits.

The two calculation methods,such as simplified variable condition method and thermodynamics method,are introduced chiefly in the paper,and used to analyze energy-loss of main steam parameter for condensing steam turbine.