Abstract: It is essential to alleviate the conflict between heating and electricity supply, and improve the flexibility of thermal power units. A heating supply retrofit by cutting off the lowpressure cylinder steam admission was made on a 200MW unit in a domestic power generation company.In order to avoid the blade flutter under low flow conditions,guided by the test data in the literature about cutting off the lowpressure cylinder steam admission, the cooling steam flow running into the lowpressure cylinder was limited to 1.0%~1.5% of the rated exhaust gas flow. After replacing the connecting pipe butterfly valve, installing measuring points on the last two stages and adding a cooling steam bypass system with desuperheating and decompression functions, heating supply and peaking load regulating capacities of the unit were calculated.Proven by data in two heating seasons,the retrofit scheme is feasible.The scheme decouples the heating and electricity capacities, lowers the condensation loss, and improves the economy of the unit.

Key words: thermal power units, cutting off the lowpressure cylinder steam admission, heat supply retrofit, cooling stream, blade flutter, peak regulation