Directing against problems existing in the control system of air-cooled island

which had been discovered in the debugging process of 600 MW direct air-cooled unit in Huaneng Tongchuan Power Plant

including oscillation of set value for the steam turbine backpressure resulting in frequently switching over of step sequence in the programme

the response of said backpressure to the switching over of step sequence having delay

without interlock for misoperation

and various complicated controls etc.

some improvement measures

such as setting delay time and time intervals

adding interlock for selection of operating condition

and simplifying control logic etc.

have been put forward.Through start-up and 168 h trial operation of the complete unit no.1

it shows that the control system after improvement is simple and reliable in structure

and flexible in regulation of the steam turbine backpressure

satisfying the requirements in operation of unit.