Generator insulation diagnostics using acoustic and partial discharge characteristics.

摘要

Unscheduled outages of the power generators as a result of insulation failure could have major technical and economic consequences. Therefore, life expansion of the units through nondestructive measurements for monitoring the electrical and mechanical integrity of the insulation has gained increasing importance. With a view to advance the ability to assess conditions and to predict breakdowns, the prevailing aging mechanisms of the generator insulation under multi-stress working environment were investigated using acoustic wave technique and partial discharge parameters. With substantial benefits to the industry for preventive maintenance programs, the work presented an intelligent insulation diagnostic system with full capability for field applications.; A novel active acoustic technique was developed to categorize the mechanical integrity of the insulation structure with sensitivity to insulation delamination and ability to predict impending failures. As a measure of structural changes a correlation model was also presented to identify the influence of the amplitude and repetition rate of PD on initiation of subsequent pulses. With the use of autocovariance and fractal dimensions of the sequential PD, the model provides significant insight into interpretation of the PD in connection with physical aspects of the activity site particularly towards the end of life.; An intelligent diagnostic system was advanced which permits identification of the stages of aging based on the data from past performance and current acoustic and PD measurements. Using a standard digitizing oscilloscope, various data handling schemes were integrated for an efficient and fast processing of the data in an industrial environment without a need for additional pulse conditioning hardware. This makes it possible to preserve the statistical and phase correlated aspects of the PD pulses from which meaningful on-line analysis can be made to assess the condition of the insulation. The system which can offer significant savings resulting from the prevention of in-service machine failures, was successfully deployed at a hydro generating station where external interference poses restrictions on the use of balanced detectors. With advantage of economical and reliability considerations, the use of the reactive power technique has also shown some promise in identifying the progress of the insulation degradation without service interruption.