Abstract: In order to solve the problem that the bushing tap TV waveform distortion of converter transformer in the high voltage DC converter stations, according to the fault recorder waveform and bushing tap voltage measurement link basic circuits, it can be obtained that the cause of voltage waveform distortion is the ferroresonance when differential pressure type capacitive voltage transformer and secondary inductive voltage transformer are applied at same time. Then resonant equivalent inductance and transformer secondary excitation impedance are calculated, and the voltage and current parameters of the bushing tap TV are actually measured according to the circuit element parameters of the measurement link circuits, which are conversed to secondary excitation impedance of transformer. So the validity of the analysis on cause of voltage waveform distortion and the accuracy of calculated value of the transformer second excitation impedance are verified. Through deducing and analyzing the measures of eliminating resonance and the circuit connection method, neutral point offset of the converter transformer caused by voltage waveform distortion of tap TV transformer is eliminated, and the protection malfunction is avoided.