Generator condition monitor evolution and capability

The generator condition monitor (also called "core monitor") had an early history of invalid alarms due to causes not related to generator overheating. Because responding to a monitor alarm involved high cost to the owner, it became common industry practice to ignore the device. Yet even on the early, somewhat primitive instruments, valid alarms occurred. Because of the potentially high value of early detection of burning inside a generator, a large effort has been expended to improve reliability of the device and make it easier to use. These efforts involved both present suppliers of this equipment, general electric & environment one, as well as others. Around 1989 a mature design had been reached, and since then over 500 of the modern devices have been put in service. Based on recent EPRI surveys and other data sources, the post-1989 monitors are now performing well, with infrequent invalid alarms. Seventeen valid alarms have been reported on generators, and these incidents are summarized individually in this paper. Although the number of valid alarms is small, because of the inherently high destructive nature of these failures the potential saving has been great . A single failure can exceed $10 million in repair cost alone, and forced outage time costs can far exceed the high repair costs. Correct response to the infrequent monitor alarm has been enhanced by the availability of the distributed control system. If properly maintained and operated, the generator condition monitor can be a valuable device that could mean the difference between a brief shut down for minor repairs or a major overhaul involving weeks or even months of costly downtime.