energies Article Using SF6 Decomposed Component Analysis for the Diagnosis of Partial Discharge Severity Initiated by Free Metal Particle Defect Ju Tang 1, Xu Yang 1 ID , Dong Yang 1, Qiang Yao 2, Yulong Miao 2, Chaohai Zhang 3 and Fuping Zeng 1,* 1 School of Electrical Engineering, ...