Space Charge Characteristics under Harmonics of Oil-paper Insulation

This paper studies the charge behavior of the converter transformer under the DC superimposed harmonic electric field, analyzes the voltage waveform of the converter transformer’s valve side bushing, and uses the frequency domain analysis method to analyze the voltage waveform and harmonics of the converter transformer’s valve side bushing at different positions. Wave type and content. Using the electroacoustic pulse method charge measurement platform, the charge characteristics of oil-paper insulation under DC superimposed harmonic environment were studied. For the position of the bushing on the valve side of the high-pressure valve hall, the AC and DC ratios are 1:7 and 1:5 respectively, which are greatly affected by DC voltage. For the low-pressure valve hall, the AC and DC ratios are 1:3 and 1:1 respectively, which are greatly affected by the AC and harmonic electric fields. Based on the analysis of the voltage waveform, the study of the charge characteristics under AC and DC electric fields has been carried out. It is found that the surface charge has a large relationship with the field strength. Under the same polarization time, the surface charge increases significantly with the increase of the field strength, while the internal charge accumulation does not change. obvious. For the same phase moment, the change of charge density at different polarization times is similar to that under DC, but the change is relatively large.