Flux monitoring improvements for on-line condition monitoring of turbine generator rotors

Abstract

Flux monitoring via air gap flux probes is a proven technology used for many years in synchronous machines to determine the presence of turn-to-turn shorts in a rotor winding. This information is critical in planning maintenance outages and in augmenting on-line vibration analysis. Traditionally, flux measurements have been done using flux probes installed on a stator wedge and a portable or permanently connected instrument. To achieve a reliable diagnostic, the signals from the flux probe had to be measured under different generator load conditions ranging from no load to full load. This requirement presented a serious obstacle in the application of this method on base load units where load adjustments are difficult. A new design of flux probe, installed on a stator tooth, and a novel approach in algorithms used to analyze measurements can help minimize the need for tests at different load conditions and still provide reliable diagnostics. This paper describes the implementation of new hardware and software and case studies that demonstrates the effectiveness of the new method in eliminating the need for load maneuvering.