Abstract: The condensate boost pump had been reformed by using of variable frequency speed control technology. After the reformation, the automatic control of the level of oxygen extractor was realized on DCS system. The difference between its reformed automatic adjustment circuit and original one was analyzed. Based on strict discussion of scheme design, the technical safety measures had been compiled, and the measures were implemented when the unit was overhaul or current repair, and the later debug was carried out, then the variable frequency automation had been put operation successfully. The results show that adopting the variable frequency controlled devices in the main auxiliaries of power plant with rational designed adjustment automatic circuit could ensure the reliability and safety of the unit operation to be not reduced, and this reformation has advantage of less input and quick results, and has active effects for energysaving and reducing the house service consumption rate.

Key words: variable frequency speed control of condensate boost pump, level of oxygen extractor, automatic control, interlock switching