To address the weak robustness and limited generalization capability of traditional machine learning-based transformer fault diagnosis methods under conditions such as data imbalance and the presence of outliers in the training dataset, this paper proposes a robust ensemble learning model for achieving high-accuracy fault diagnosis of power transformers. Firstly, to mitigate the impact of outliers on model robustness, the correntropy loss (CL) is introduced into the traditional extreme learning machine (ELM) framework, and the gradient-based optimization is used to obtain the optimal solution, which results in a novel robust learning model, called CL-enhanced ELM (CLELM). Additionally, the snow ablation optimizer (SAO) is employed to optimize the hidden layer weights and biases of the CLELM, further improving its performance. Secondly, to enhance the generalization capability of the model, multiple SAO-CLELM models are weighted and combined to form a robust ensemble learning model. Finally, to address the data imbalance issue in the transformer fault dataset, the synthetic minority over-sampling technique (SMOTE) is employed to augment the data, and the balanced training data is used to train the ensemble SAO-CLELM model for fault diagnosis classification. The fault diagnostic performance of the proposed integrated SAO-CLELM model is validated under two different fault test sets, and the experimental results demonstrate that the proposed model can achieve accurate fault classification results, indicating its high level of robustness and generalization ability.