Study Of The Typical Insulation Defects Partial Discharge Models In The Gas Insulated Switchgear(GIS)

Gas Insulated Switchgear(GIS for short) is an important distribution device in the ultra-high voltage grid considering its small and excellent technical performance.However,from operation and maintenance experience,insulation faults have been exerting considerable influences on GIS's working reliability. Partial Discharge(PD for short), being the early manifestation of insulation faults within GIS equipment, poses a potential threat to the normal operation of GIS. If partial discharge is detected and removed as early as possible during operation, the equipment loss will be minimized and the power supply reliability will be improved. Thus, researching on and preventing partial discharge in GIS has become a great subject nowadays. By employing several hand-made experimental models on common insulation faults, this paper has studied the related electrical characteristics in terms of each fault, and has reached some conclusions after a series of experiments.By using self-made needle-to-plate corona discharge experimental model which is stable in discharging and well in discharge repeatability, this paper has found a method of comparing intensity of characteristic spectral line which can identify the strength of discharge. With the detection method combining UHF discharge signals and discharge optical emission spectra, it is pointed out that the connections between these two factors.Small cavity air gaps, which are easily observed and micro bubbles with small size and stable in discharging, are made by machining operations and laser carving technology respectively. Physical model of arc-shaped cavity is presented and the reason is explained why the phase distribution of the current pulse of air gap discharges is relatively concentrated and no zero-crossing phenomena under high voltage is found. By using zoom lens to take pictures of the air gap discharge in the cavity, the original place of discharge in the cavity is identified and the rationality of the physical models of arc-shaped cavity is verified. Although micro bubbles made by the laser carving technology are steady in discharging and function well in repeatability, they have short service life.This paper developed fixed suspension and free mental particle models which are stable in discharging and well in discharge repeatability. Analysis discharge characteristics of metal and nonmetal fixed suspensions, found the surface electron emission is the main factor affecting the metal suspension needle discharge, while the wall charges are the dominant effect of nonmetal needle suspension discharge.