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The resolve of journal bearing field problems and the full vibrational assessment of an industrial gas turbine, simple cycle rotor train, ABB’s GTllN2 is presented. Three units experienced several times damage of the journal bearings on the compressor end. The analysis of the damage, including tests, indicated that insufficient jacking oil flow was the cause. The jacking concept was corrected and starting history has proven reliable operation, resulting in not one additional failure.During the same period, two last stage blades failed in one of the units damaging neighboring blades additionally. The machine tripped under the unbalance. Some auxiliary piping and the babbitt of the journal bearing was damaged. However, the rotor came to a safe stop with only some rubbing, and the turbine casing fulfilled its containment function perfectly.In order to better understand the dynamic behavior of the train, an extensive vibration measurement program was decided between Kentucky Utilities and ABB, and executed by Bently Nevada. The results proved excellent rotor balance, verified original design parameters, and no fluid induced instabilities were found. This joint effort allowed to fully assess and prove the rotor dynamic integrity of the gas turbine.

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The features of composite insulators using silicone rubber in high-voltage circuit-breakers are presented. The paper describes the design, testing and field experience with composite insulators over the past ten years.

Abstract-A method for achieving a controlled arcing time on high voltage (SF 6 ) circuit breakers during fault interruption is presented. Using least mean squares based regression, a model of a sampled (fault) current is generated. If the model is found to sufficiently match the sampled current, the model is extrapolated to predict current zero times for use as targets for synchronizing the opening command to the circuit breaker so as to achieve a pre-determined optimum arcing time. Prediction of target current zero times within ±0.2 ms have been achieved. Benefits of such controlled interruption include reduction in circuit breaker electrical wear, potential to increase circuit breaker switching ratings and facilitation of new high voltage interruption techniques. Novel aspects of the scheme include the use of an hypothesis test for verification of the accuracy of the modeled current.