**3. Condition Diagnosis Model for Main Transformer**

Condition diagnosis model is important to verify the feature selection algorithm and to determine the accuracy and rapidity of transformer condition diagnosis. SVM is a machine learning method based on statistical learning theory, compared with other algorithms, it can well solve practical problems such as small sample, nonlinear [11], the PSO algorithm can converge fast in the parameter optimization. The SVM optimized with PSO in the field of power transformer fault diagnosis has further application [12].
