PROJECT TITLE :

PD characteristics of oil-pressboard insulation under AC and DC mixed voltage

ABSTRACT:

The insulation downside of converter transformers has become one amongst the core issues in HVDC system, which is receiving more and a lot of attention. A converter transformer has complicated structures and needs high insulation level. The voltage waveform which the converter transformer insulation withstands is different from AC transformers. In the valve aspect of the converter transformer, the insulation endures a mixed voltage of AC voltage, DC voltage, harmonics and therefore the pulsating component etc. Partial discharge (PD) occurring in oil-pressboard insulation is the one in all the most causes of insulation breakdown, and it's the most factor of electrical aging of materials. Even though PD characteristics underneath pure AC or DC voltage waveform have been studied by several researchers, very little research has been done with the mixed voltage. In this paper, the AC + DC mixed voltage experiment system is founded to review the PD characteristics underneath mixed voltage waveforms. The study results indicate that the pressboard withstands most of the DC element and void withstands most of the AC part when applied mixed voltage. For PD inception voltage, it is set by each the AC component and DC part. For PD development, AC element has a lot of vital influence than DC element. However, the DC part is found to market PD activity underneath AC 0.5 cycle with the same DC polarity and inhibit PD activity under AC 0.5 cycle with the opposite DC polarity. The results in this paper offer an experimental foundation for the converter transformer insulation breakdown mechanism and analysis.