The coal mill is one of the important auxiliary machines in thermal power units
and its operating status plays a significant role in the stable output and safe operation of the unit. Therefore
researching fault warning methods can effectively reduce the probability of unexpected shutdown of the coal mill and improve the overall reliability. By integrating the advantages of various deep learning methods
we propose a fault warning method based on attention mechanism CNN-BiLSTM. CNN is used to learn spatial features
and BiLSTM is used to learn temporal features. Finally
attention mechanism assigns different weights to the extracted spatiotemporal features based on their importance
thereby amplifying the influence of critical features during the computation process and elevating the model's predictive performance. A 660 MW thermal power unit's coal mill is used as a case study. The validation results show that the proposed method exhibits higher prediction accuracy than the comparison methods during the normal stage and a more pronounced upward trend in prediction residual during the fault stage. In order to further improve the performance of fault warning
we introduce the relative entropy index to process the residual. The experimental results show that the relative entropy index solves the shortcomings of the residual control chart and effectively improves the fault warning effectiveness and warning time. Specifically
the proposed method can issue a warning for coal mill bearing faults 33 minutes ahead of time.
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