SURVEY OF SOURCES AND ANALYSIS OF REASONS OF THE TURBINE SETS ELECTROEROSION DAMAGES

The article is dedicated to the actual problem of electroerosion damages of critical joints and parts of turbine sets. The enumeration of typical causes of such damages is presented. It is shown that electromagnetic processes may also defl ect the indications of instruments in control and diagnostic systems of turbine.

The sources of electric current are determined which may cause electroerosion destructions of equipment, such as static electricity, induced voltage impulses on shaft-line elements in relation to static parts, parasite currents of generator rotor, unipolar electromotive forces. The developing mechanisms of such damages are considered which are individuated for every particular source.

It is note that due to improper functioning of grounding brush the cause of damage becomes static electricity, accumulated on the turbine shaft-line. In case of diminishing of isolated bearings isolation resistance down to unallowable values the destruction of joints and parts are caused by the action of parasite generator currents. The high level of residual turbine sets magnetization may bring about the appearance of unipolar electromotive forces and connected to them avalanche increasing of current value, flowing through working surfaces bearings leading to their destruction.

On the basis of carried out analysis of destruction reasons the main requirements are formed assuring the elimination of sources of appearance and development of electroerosion processes, that is: security of adequate functioning of grounding brush as well as satisfactory condition of isolation of isolated bearings, strict demand for fulfillment of measuring of residual magnetization of turbines during their capital repair and in case of necessity carrying out demagnetization alongside with development and implementation of automatic systems for on-line control of electromagnetic control of turbines together the systems for suppression of induced voltage impulses on shaft-lines.

It is stated that the fulfillment of these requirements will allow to minimize the risks of electroerosion destruction in turbine and to avoid the eventual outing of equipment. 

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