Generator Recovery Project Case Study

The Generator Recovery Project Case Study is a technical paper that will discuss a project which started with a simple open, clean, and close of a 40MW air cooled generator and turned out to be much more. The unit experienced a gradual increase in winding temperatures over the last several years, with a more notable increase in phase B temperatures. In the history of the unit, it was observed that the unit became contaminated with carbonaceous deposits due to the environment in which it operated. Routine cleanings during scheduled outages were successful in lowering the increased temperature trends. With today’s market environment and an increasing commonality of extending outage intervals, the routine outage interval had been extended to 7 years from the previous outage. The scope of work was to remove the rotor, clean, inspect, test and return the unit to service in just over one week’s time. The requirements of the project were that the efforts be maximized so that the unit returned to service in the most economical means while adhering to practices that would maximize the unit’s availability and reliability. With findings of significant contamination of carbonaceous deposits and significant foreign object damage (FOD), the project lead to overwhelming questions and concerns. The case study will discuss the immediate concerns of the unknown, such as if the core was even recoverable and what was the source of FOD. The case study will walk through the questions raised and the actions taken to first assess the condition of the unit and what actions to be taken to recover the core damage, if at all possible. Most importantly, determining the source of FOD and the rectifications to eliminate future sources of FOD from this area. Detailed information on repair assessments and validation will be presented and procedures for repair and recovery will be discussed. Final testing and validation to return to service will be discussed and the operational characteristics after the repair will be revealed.