Experimental Studies on the Motion and Discharge Behavior of Free Conducting Wire Particle in DC GIL

Abstract

-This study aims to restrain free conducting wire-type particles which are commonly and dangerously existing within DC gas-insulated transmission lines. A realistic platform of a coaxial cylindrical electrode was established by using a high-speed camera and a partial discharge (PD) monitor to observe the motion, PD, and breakdown of these particles. The probabilities of standing or bouncing, which can be affected by the length of the particles, were also quantitatively examined. The corona images of the particles were recorded, and particle-triggered PD signals were monitored and extracted. Breakdown images were also obtained. The air-gap breakdown with the particles was subjected to mechanism analysis on the basis of stream theory. Results reveal that the lifting voltage of the wire particles is almost irrelevant to their length but is proportional to the square root of their radius. Short particles correspond to high bouncing probability. The intensity and frequency of PD and the micro-discharge gap increase as the length of the particles increases. The breakdown voltage decreases as the length of the particles decreases.

Research on discharge phenomenon caused by cross‐adsorption of linear insulating fibre and metal dust under DC voltage

“…As the radius of the particles is very small compared to the air gap, it can be considered that the strength E 0 ( t ) of the particles is equivalent to the field strength between the entire plates, that is, E 0 ( t ) = U ( t )/ d , Where d is the distance between the electrodes. The coulomb force of the particles is: where q is the charge carried by the particles, and k is the correction factor caused by the image charge [11, 28–31]. where a is the radius of the particle and l is the length of the particle.…”

“…In the electric field, supporting force F, gas buoyancy F v , coulomb force F q , gravity G, and gas viscosity resistance F f are the main forces on the particles [28][29][30][31], as shown in the Figure 3. Studies have shown that F f and F v can be ignored [11,30].…”

“…where q is the charge carried by the particles, and k is the correction factor caused by the image charge [11,[28][29][30][31].…”

“…Around the 1970s, scholars conducted some researches on insulating dust [5][6][7][8][9][10], and generally believed that the insulating objects were not harmful and did not even produce obvious movement behaviours [10][11][12], which has been universal accepted until nowadays. Therefore, current domestic and foreign scholars' researches on impurities in gas insulated switchgear (GIS)/GIL mainly focus on metal particles of millimetre-level and above [11][12][13], which they generally believed could be more harmful to the insulation. While, there were little research on insulating fibres and metal dust.…”

A Fault Diagnosis Scheme Using Hurst Exponent for Metal Particle Faults in GIL/GIS

“…Traditional metal particle fault identification is mainly achieved by using ultrasonic amplitude, collision frequency and apparent discharge quantity from the original signal as the feature vectors of particle fault identification [ 8 , 9 , 10 ]. However, it may cause overlapping, confusion and missing of fault features, which can result in long diagnosis time and low diagnosis accuracy, due to the problems of airgap discharge and random change of collision angle when particles are moving in the electric field.…”