Design of PD Test and Measuring System at DC Voltage

Abstract: A set of PD test and measuring system at DC is built, which is composed of discharge impulse waveform ultra-wide band measuring system and ultra-high frequency signal measuring system. Six kinds of oil-paper insulation PD models are designed. Test results indicate that the defect model discharges stably and its repeatability is good at the same conditions; the measuring system can detect the discharge impulse waveform and ultra-high frequency signal correctly. It provides a research platform for on-line monitoring of PD discharge single waveform, impulse sequence and ultra-high frequency signal.  

Key words: DC, Partial discharge (PD), ultra-wide band measuring, ultra-high frequency measurement         

Introduction

The DC transmission underwent the development of ±100, ±250, ±400, ±450, ±500 and ±750kV and ±800 UHVDC technology is being developed now. The insulation condition of converter transformer is directly related to the reliability of DC transmission. However, with the continuous improvement of DC transmission voltage stage, related oil-paper insulation of electric equipment will generate DC partial discharge at some weak links, which poses a threat to equipment. Hence, it is of significance to study DC partial discharge of oil-paper insulation. The PD test and measuring system at DC are established in this paper. Measurement of discharge impulse waveform and ultra-high frequency signal are performed on designed typical oil-paper insulation models (oil-paper needle-plate, oil-paper parallel plate gap, oil-paper surface, oil-paper internal defect, oil-paper wedge and oil-paper floating discharge) at DC.