Gas Insulated Busduct Research Articles

Effect of Functionally Graded Material of Disc Spacer with Presence of Multi-Contaminating Particles on Electric Field inside Gas Insulated Bus Duct

Solid insulators play a crucial role of electrical insulation in gas insulated power equipment. In order to improve the insulation performance of the solid insulators, two technical points should be considered, the first is the improvement of the insulation performance and the second is the control of the electric field distribution in and around the solid insulating spacers. Practically the insulation performance around the spacer can be improved by various techniques, such as; controlling the spacer shape, adding shield electrodes for electric field relaxation, the introduction of an embedded electrode, etc. These techniques lead to a more complicated structure of the equipment and increase the manufacturing cost. Thus, it is necessary to propose a new concept on solid spacers with keeping their simple structure and configuration. In this paper, a functionally graded material (FGM) is proposed to minimize the electric field distribution around the spacer, specially, on triple junction point, which was one of the important factors dominating a long-term insulating property of solid delectric. Finite Element Method (FEM) has been used throughout this work, for its favorable accuracy, to calculate the electric field distribution inside the bus duct. The Electric field distribution around earthed particle contamination which adhered to uniform and FGM of disc-spacer is presented. The effect of distance between particle and spacer on the electric field values is investigated. The effect of hemi-spherical radius and length of particle on maximum electric field at triple junction point is also discussed. Electric field relaxation effect (EFGM/Euniform) by introduction of the U-shape FGM spacer is also presented. The electric field distribution along the surface of FGM of disc spacer with presence of multi-contaminating particles at various positions is presented. DOI: http://dx.doi.org/10.11591/ijece.v3i6.4354

Dynamics of Metallic Particle Contamination in Gas Insulated Substation (GIS)

This paper analyses the movement of free conducting particles inside a single phase Gas Insulated Bus duct(GIB).A two dimensional mathematical model was proposed for determining the movement pattern of metallic particle in GIB by considering all the forces acting on the particle like gravitational, drag and the electric field forces. These particles may be free to move in the electric field or may be fixed on the conductors, thus enhancing local surface fields. Electric fields at the instantaneous contaminated particle locations were computed using Charge Simulation Method (CSM).To determine the particle trajectory in a single phase Gas Insulated Bus duct (GIB), an enclosure diameter 152 mm and conductor diameter 55 mm is considered. The simulation of the particle movement was carried under different AC voltage levels like 100KV, 132KV, 145KV and 175KV class enclosure of GIB for aluminum, copper and silver particles. The results of the simulation have been presented and analyzed in this paper.

Estimation of Transient over Voltages in Gas Insulated Busduct from 220kv Gas Insulated Substation

The transient over voltages are generated in gas insulated substations (GIS) during switching operation of substations in the order of a few nanoseconds. These transients have traveling wave behavior and travel to external systems through discontinuities and interface such as enclosures, bushings, cable joints etc. Depending up on configuration of the GIS and the amplitude of the electric and magnetic fields could be of the order of a few tens of kilovolts per meter and a few hundreds of amps per meter respectively. These very fast transient over (VFTO) voltages create critical situations in protection circuit and control circuit and makes raise faults in cables, transformers and secondary circuits, which result in malfunctioning of the primary equipment. The suppression of VFTO is very important in GIS systems. In this paper, included estimation of transient voltages in the switching operations has been calculated due to transient field with respect to 220kv gas insulated substation during switching operation. The effect of Transient field have been analyzed and clearly demonstrated for substation by develop of suitable simulation model to estimate over transient voltages. The proposed approach successfully implemented in the platform of MATLAB software.

Movement of Metallic Particle Contamination in a Gas Insulated Busduct under Dielectric Coated Enclosure with Electromagnetic Field Effect

The purpose of coating the inside surface of gas insulated busduct (GIB) enclosure with a dielectric material reduces the deleterious effect of electrode surface roughness, impedes the development of metallic particle initiated micro discharges, increases the field required to lift particles, and reduces the charge acquired by particles. The performance of particle contaminated compressed gas systems with dielectric coated electrodes are analyzed in this paper. The equations governing the motion of the particle due to its electromagnetic field effect has been formulated to obtain the particle trajectories. Hence simulation has been carried out to study the effect of fields on the motion of the particle with and without electromagnetic field effect under dielectric coated enclosure. Particle trajectories obtained for various voltages of aluminum, copper, and silver particles of size 12 mm in length and 0.2mm as radius present on the enclosure. The simulation results have been presented and analyzed.

Modelling and Analysis of Metallic Particle Movement in a Common Enclosure Gib With Electromagnetic Field

Compressed gas-insulated substations (GIS) consist basically of a conductor supported on insulators inside an enclosure, which is filled with sulphur hexafluoride gas (SF6) . The voltage withstand capability of SF 6 bus duct is strongly dependent on field perturbations, such as those caused by conductor surface imperfections and by conducting particle contaminants. The contaminants can be produced by abrasion between components during assembly or operations. These particles can either be free to move in the GIS bus or they may stick either to an energized electrode or to an insulator surface. If a metallic particle crosses the gap and comes into contact with the inner electrode or if a metallic particle adheres to the inner conductor, the particle will act as a protrusion on the surface of the electrode. A study of CIGRE group suggests that 20% of failure in GIS is due to the existence of various metallic contaminations in the form of loose particles. The presence of contamination can therefore be a problem with GISs operating at high fields. If the effects of these particles could be eliminated, then this would improve the reliability of compressed GIS. It would also offer the possibility of operating at higher fields to affect a potential reduction in the GIS size with subsequent savings in the cost of manufacture and installation. The purpose of this paper is to develop techniques, which will formulate the basic equations that will govern the movement of metallic particles like aluminium and copper in a three-phase gas-insulated bus duct. The simulation also considers the electromagnetic field effect on particle movement and the results have been presented and analyzed.

Shielding Effectiveness of the Gas-Insulated Bus Duct for Transient EM Fields Generated in a GIS During Switching Operations

Characterization and quantification of the transient electromagnetic (EM) fields generated in a gas-insulated substation (GIS) during switching operations has become important in recent years. This is due to increased use of sensitive electronic devices in the control circuitry of such substations. In this paper, a numerical model based on the finite-difference time-domain technique has been developed to compute the EM field emission from the gas-insulated bus duct through nonmetallic flange of the support insulator during switching operations. The shielding effectiveness (SE) of the bus duct/section for the EM fields has been evaluated using a derivative Gaussian current source and a short time sinusoidal current source. The effect of variations in dimensions of the slot formed by the nonmetallic flange as well as electromagnetic properties of the insulator/bus duct enclosure on SE has been studied. The variation in field pattern along the axis of bus duct at various distances due to the transient currents of different frequencies has been analyzed. The enhancement factor for the EM field levels due to the presence of a metallic structure has been reported. Finally, emission levels are calculated for the very fast transient currents generated in a 245 kV GIS and their dominant frequencies have been identified.

Time dependence of AC flashover characteristics for particle-initiated breakdown in GIS

The AC flashover characteristics for wire-particle-initiated breakdown and its time dependence were studied in a realistic 362 kV SF/sub 6/ gas-insulated bus duct. The voltage leading to breakdown after two hours was calculated from studies of the time to breakdown at different voltages. The calculations were made for different pressures and compared with the experimentally obtained two-hour withstand voltage. The influence that the long-term exposure to voltage has on the particle was studied, including both the particle deformation and the impact that the deformation has on the particle movement pattern and the AC flashover characteristic. It was found that the deformation taking place at the ends of the wire, depends on the wire material and diameter and on the duration of the voltage application. In some cases it plays a decisive role in the time dependence of the AC flashover characteristics.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Three Dimensional Magnetic Field Analysis OfThree-phase Gas Insulated Bus Duct

When any fault occurs in a gas insulated bus duct used in the gas insulated switchgear(CIS), magnetic field outside the duct will change due to the fault current in it, so the internal fault will be detectable by sensing the change of the magnetic field. In this paper, a three dimensional magnetic field analysis of three-phase bus duct is investigated, and the results are compared with the measurements. Accuracy of the analysis has been verified and the method of installing the sensors to obtain high sensitivity is clarified.