Abstract: Aiming at interference from stray capacitance, overlapping traveling waves and leakage current masking faint faults in DC insulation monitoring of salt-field PV stations, an online localization method is proposed. Tikhonov regularization retrieves dielectric relaxation parameters to decouple insulation resistance from humidity; singular spectral entropy of traveling-wave refraction coefficient plus random forest identifies faulty strings; adaptive Kalman filtering with sliding-window slope compensation restrains background leakage below 5 μA. Field tests detect hidden corrosion faults with median localization error 2.3~3.1 m, false alarm rate 9.7% and missing alarm rate 4.4%, realizing meter-level online early warning.