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

Abstract

A large amount of metal dust is often generated during production and operation of Gas Insulated Switchgear/Gas-Insulated Transmission Line, and insulating fibres are very easy to mix in during assembly. The discharge phenomenon induced by these two impurities remains unknown. By setting up a test rig with parallel electrodes, the discharge characteristics of metal dust and linear insulating fibres under the negative DC voltage were studied separately and jointly. The obtained research results indicate some interesting phenomena that the metal dust may render 'sand storm' motion characteristics under the action of the electric field, and the linear insulating fibres appear to show 'standing', 'jumping', 'flying fire' and other phenomena. A small amount of dust and fibres alone present little effect on the breakdown voltage of the air gap. However, while the insulating fibres and metal dust coexist, the metal dust will be adsorbed on the surface of the insulating fibres, then the surface charge of the fibres is reallocated, and the discharge phenomenon at both ends of the fibres is enhanced, so that the insulating fibre exhibits similar movement and discharge characteristics to the linear metal particles. At the same time, the fibres with dust absorbed on will result in an air gap breakdown voltage drop of approximately 25%-40%. What's more, if the discharge of fibres and the 'sand storm' movement of the dust coexist, it may directly lead to 'explosion' of the moving dust, causing severely ablation of the plate surfaces, and thereby the degree of destruction increases dramatically.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

China's 10-year progress in DC gas-insulated equipment: From basic research to industry perspective

“…In particular, in most cases the metal particle shows reciprocating motion between the two electrodes. However, when the coaxial electrode is arranged and the negative DC voltage is applied, the linear and flaking particles present the phenomenon of " flying firefly", which not only bump around the high-voltage electrode, but also do not contact the ground electrode [136,137] , as is shown in Figure 34. In addition, for the movement characteristics of metal powder under DC voltage, there is a phenomenon similar to sand storm [138,139] .…”

“…The surface coating of electrode and the addition of particle collector are important means to limit the impact of metal particles on insulation. Many studies have shown that the surface coating has no contribution in moving the particle to the low electric field area, however, it prevents the particle from lift-off by limiting the charge of particle, thus avoiding the disorderly movement of particles in the equipment [139][140][141] . The particle collector is designed with a suitable structure to set a low field area, which can induce the metal particle move into it and limit their motion activity.…”

Towards the surface flashover in DC GIL/GIS: the electric field distribution and the surface charge accumulation

“…On the other hand, the microstructure and the interaction of the dust can also lead to the distortion of the electric field and induce the surface charge. Due to these two factors, the more area adsorbed by the dust, the more serious the electric field distortion is, resulting in higher electric field and flashover [58].…”

Significantly suppressing metal particle-induced surface charge accumulation of spacers in DC gas-insulated power transmission lines

“…However, during the production, transportation, assembly, and operation of gas-insulated unit, the metal particles can not be avoided. Notably, there have already been a considerable documents showing that the risk of insulation failure is increased due to the presence of surface charge accumulation and metal particles [5][6][7][8][9].…”