Corrosion and Deposits in Water-Cooled Generator Stator Windings: Part 1: Behaviour of Copper

The most common and severe problem that has arisen with generator water cooling throughout its more than 50 years of history is plugging of copper hollow conductors. A 4-step model of the occurrence of this plugging was developed to indicate the influencing parameters. The steps are oxidation of the copper surface, release of the oxidized copper, migration of the released copper, and re-deposition of the migrating copper. It is observed that these steps are influenced by water chemistry as well as by system and component design. From the operating side, adherence to a suitable water chemistry regime as well as proper lay-up practice help to avoid or mitigate flow restrictions.