At some 300 MW steam turbine generator,vacuum sealing oil tank magnetism vane liquid meter fixed a level,and it is not changed as oil tank's actual level.In order to resolve this problem magnetism vane liquid meter,floater and related components are checked.Finally it is the level switch which has big magnetic force with the floater.

The turbine has the problem that the upper and lower casing temperature difference is too big during hot start process.The paper point out that there is design defect in the drainage system and proposes the modification suggestions.After modification,the temperature difference is about 20℃ during hot start.