Moving behaviors and harmfulness analysis of multiple linear metal particles in GIS

Metal particle could be produced in the production and installation process of GIS, whose free movement is a significant security risk to GIS. At present, some related research focus on the movement behavior and partial discharge of individual particle, but for the movement behaviors and harmfulness of multiple particles are not very clear. In this paper, the 126 kV GIS prototype proportion shrinking test chamber was set up, the different number of metal particles with same size (10 mm length, 0.25 mm radius) were placed in the chamber, the movement behaviors of multiple particles were filmed by using a high speed camera, and discharge signals were recorded with the conventional pulse current detector and ultrasonic detector. The results of the study indicate that: At the operated voltage, the single particle (10 mm length, 0.25 mm radius) has a small jumping height but a high jumping frequency, and there is basically a collision case in each power frequency cycle. The number of linear particles affect the lifting voltage, and with the increase of the number of neighboring particles, the lifting voltage decrease, such as the lifting voltage of two aluminum particles with 10mm length and 0.25 mm radius could be reduced to 84% of the lifting voltage of a single particle, and the lifting voltage of eight aluminum particles could be reduced to 77%. Compared with single particle, the number of ultrasonic signals and partial discharge pulses of multiple particles becomes more obvious, and it could occur multiple collisions in a half power frequency cycle, but for a single particle, the maximum number of linear particle's collision in a half power frequency cycle is only one. With the increase of applied voltage, the flight time of the particles were significantly longer, and multiple discharge pulses were detected during a single collision, whose position showed “V” type distribution. At the operated voltage, the single linear particle had less harmfulness, while the existence of multiple linear particles, could greatly reduce the insulation strength of GIS, such as eight neighboring aluminum particles with 10 mm length and 0.25 mm radius could lead to a breakdown in the vicinity of the operated voltage, but the same size of the individual particle has not yet led to the breakdown of the test chamber at even twice of operated voltage. Under the different voltages, the maximum value of histogram of n-T/2 of linear particles remained unchanged, and through the histogram of n-T/2, it could estimate the number of particles in GIS.