Corrosion and Deposits in Water-Cooled Generator Stator Windings: Part 3: Removal of Flow Restrictions

摘要

Flow restrictions in generator stator bar hollow conductors can be removed either mechanically or chemically.Both methods have their advantages and disadvantages and in certain cases only a combination of both leads to success.Mechanical cleaning can open up completely plugged hollow conductors at the inlet or outlet of the bars,while chemical cleaning thoroughly removes all copper oxides,also within the bars.However,as with all chemical cleaning methods,there must be access for the chemicals to the copper oxide deposits so the chemicals can dissolve and remove the plugging.To prevent metallic deposits,it is important that the chemical cleaning be performed under oxidizing conditions.Additionally,it might also be useful to apply a post-cleaning surface treatment under certain conditions.It is recommended to take any kind of plugging seriously and to start reacting when first signs of plugging occur.Once severe conditions have developed,this might lead to power downrates,a decrease in insulation lifetime,forced outages or in the worst case even irreversible damage to the generator.