SF6 Gas Insulated Switchgear Research Articles

A Linear Capacitive Sensor for ppm Moisture Measurement in SF₆ Gas-Insulated Switchgear

Moisture measurement and control is very essential for gas-insulated switchgear (GIS). For safe and reliable operation, the moisture inside GIS needs to be kept within the prescribed limit. This article presents a capacitive sensor for traces of moisture measurement in SF6 gas used in GIS. The sensor is fabricated using fluorine-doped tin oxide (FTO) glass as the base substrate and silver as the upper electrode. A thin film of porous alumina (Al2O3) is used as a sensing layer for detecting the presence of moisture at parts-per-million (ppm) scale. The performance of the presented sensor is experimentally validated for different moisture concentrations in SF6 gas. The sensor shows a good sensitivity (0.238 pF/ppm) with linear characteristics (±2.05%) over the moisture range of 246-725 ppm. The response of the fabricated sensor is very accurate (±0.84%), with low hysteresis (±0.32%) and highly repeatable (±0.013%). All the data of the fabricated sensor are obtained experimentally that validate its use for an effective moisture measurement in GIS where the live conductors and other electrical equipment are surrounded by SF6 gas. The cost-effectiveness of the sensor is ensured because of its simple fabrication process and robust design.

Classification of Partial Discharge Fault Sources on SF₆ Insulated Switchgear Based on Twelve By-Product Gases Random Forest Pattern Recognition

Sulphur hexafluoride (SF6) gas insulated switchgear (GIS) is widely used in electrical power supply system and therefore needs regular preventive maintenance. Prediction and diagnosis analysis of faults in GIS using SF6 gas by-products was introduced previously by using 4 to 8 types of by product gases. As latest development on gas analyser, more by-product gases can be detected and used for condition monitoring of the GIS. The type, number, concentration and chemical stability of by-product gases of SF6 GIS are found to be closely correlated to the type of defect. However, the number of by-product gases used increases, the pattern for faults classification become more complex. Thus, further analysis on increasing number of by product gases using intelligent techniques such as pattern recognition is required. In this article, 12 significant by-products captured due to various sources of partial discharge fault in GIS were used. Random Forest (RF) was selected in this work as a multi-class classification technique. The analyses using RF pattern recognition with eight algorithms based on the presence and concentration of the gas by-products were carried out. The RF algorithm successfully recognises a given defect with an accuracy of 87.5% for all defects fault classification. The performance of the RF algorithm is 1.5 times better than the decision table algorithm which is the next best algorithm. This research illustrates the feasibility and applicability of an effective GIS diagnostic using gas by-products analyses, and in particular, using the RF pattern recognition.

배전용 가스절연개폐기 부분방전 진단의 적정 주파수 분석

In order to improve the accuracy of partial discharge diagnosis by distinguishing internal partial discharge and external noises in distribution grade SF6 gas-insulated switchgear, partial discharges were measured for the on-site operated switchgears. Floating discharges due to water immersion defect in bushing, SF6 gas leakage defect, poor conductor-contact defect etc. were considered as internal discharges, and discharge by peeling semi-conductor paint in bushing was considered as external discharge. As a result, the main frequency bands of internal and external discharges were identified, and it was proposed that frequency bands of the partial discharge sensor would be designed in the range from 250MHz to 350MHz for detecting internal partial discharges.

Enhanced Method for Pressure Rise Calculation in SF6 GIS Due to Fault Arcs

Modeling of pressure rise in SF6 GIS (Gas Insulated Switchgear) due to internal arc faults is a complex and challenging task, due to a large number of highly variable factors, which influence the whole process. This is especially the case in GIS with high rated short circuit currents, where the effects, such as material evaporation and erratic arc behavior, and consequently the pressure build-up rate, are much more pronounced. These severe conditions ultimately determine the design limits and must therefore be carefully investigated. The enhanced internal arc simulation model, presented in this paper, considers the impact of evaporation of different materials on gas properties and the pressure rise, as well as the dependence of released arc energy, thermal transfer and evaporation intensity on the state of gas. The experimental set-up and the test configuration, used to validate the calculation results, are evaluated and discussed. An evident finding, which is supported by measurements, is that the implemented improvements of the basic simulation model (introduced in the Technical Brochure 602 by the CIGRE working group A3.24) increase the prediction accuracy of GIS withstand performance during internal arc faults.

Environmental and safety aspects of AirPlus insulated GIS

New insulation gases as alternatives to SF6 have been presented in the last years. The main focus has been on technical performance and reduced global warming potential compared with SF6 gas-insulated switchgear (GIS). Another very important aspect for customers is the environmental impact and safety in all operational situations, as well as during leaks or even internal arc failures. This study introduces a solution using AirPlus™ as an insulation gas mixture, with results of comparison tests to SF6 GIS and air-insulated switchgear.

광대역 및 협대역을 동시에 사용하는 부분방전 측정 시스템 모듈 개발

Power plant is that very high reliability when industrial and economic impact on the overall electric power system is required, it is essential to improve the reliability, especially the fault prediction diagnosis. Since an accident caused by the partial discharge in the power plant is above state has a faster response characteristic than the other indications in the case of any, the partial discharge generated in the power plant immediately detect the deterioration of insulation due to the accident of the power plant and the non-drawn It should prevent or reduce.BR Partial Discharge Measuring Systems for UHV SF6 Gas Insulated Switchgear and power transformer on site installed has some probability of abnormal recognition in case of non-flexible deal with on site noise. Many methode to eliminate these kinds of noises, UHF Detection System is chosen as purchase description in Korea, but this system having a bandwidth between 500㎒ 1.5㎓ wide band. Initial install periods(about 20 years ago), this band had no strong signal source, but in these days this wide band have strong signals, such as LTE. So, module described in this paper is designed as simultaneously use with wide and narrow band for solve this noise problem, and introduce this system.

Insulation condition monitoring of epoxy spacers in GIS using a decomposed gas CS2

The epoxy spacers in SF6 Gas Insulated Switchgear (GIS) are vulnerable to discharge. Once the surface of the epoxy spacers is deteriorated under discharge, insulation break down may occur subsequently. From a number of experiments carried out on 110 kV GIS, a new gas CS2 was detected when creeping discharges occur on the epoxy spacer surface. In order to verify the correlation between CS2 and the degradation of epoxy spacers, the quantum chemistry analysis was used to investigate the mechanism of CS2 development. Based on the results, the relation between CS2 and spacer insulation degradation was determined.

Finite Element Analysis of Sealing Structures for SF6 Gas Insulated Switchgear

The sealing equipment of the SF6 GIS including the rubber O-ring and bolts were numerically simulated. Effects of bolts number, the tension moment of bolts, and gas pressure on contact stress and peak stress of O-ring were mainly studied. Simulated results showed that the bolts number and tension moment of bolts has a great effect on the sealing performance of mechanical seal and the maximum stress of O-ring. The higher contact pressure could be achieved under the condition of a larger bolts tension moment and bolts number and smaller gas pressure, but it also results in a reduce of life of O-ring.

Applying a Voice Recognition System for SF6 Gas Insulated Switchgear's Inspection/ Maintenance Services

The authors have developed a new set of portable voice recognition systems that are compact, lightweight, and have two-way communication (sending and receiving) for the purpose of inspection/maintenance services for substation equipment. The authors are using these newly developed systems for daily visual inspection, periodic inspection, and commissioning tests of substation equipment. By applying these systems with the added guidance and judgment functions, it is possible for unskilled personnel to carry out inspection/maintenance services of substation equipment. It is possible to feed the data collected at the site directly into the computer, and the trend control management can be done easily. This paper outlines the voice recognition system, the applied examples of SF6 gas insulated switchgear's (GIS) periodical inspection/maintenance, and the achieved results.

Characterization of GIS Spacers Exposed to SF6 Decomposition Products

SF6 gas-insulated switchgear is a sealed system, but low- level contamination can accumulate and affect spacer performance. The degradation of a number of spacer materials exposed to either direct arcing conditions or arc by-products was investigated to correlate their surface molecular features with changes in electrical performance. Electron Spectroscopy for Chemical Analysis, Scanning Electron Microscopy, Infrared and Thermal Analysis were used to probe the surface of the dielectrics. In the immediate vicinity of the spark, spacer surfaces undergo irreversible chemical, morphological, and physical changes with extensive pyrolysis and surface erosion. There is clear evidence of chemical reactions with high concentrations of fluorine bonded to the organic resin. Exposure of spacer materials to SF6 arcing by-products results in significant reduction in electrical properties with profound changes in the chemical structure of both epoxy moieties and/ or filler particles. This paper will describe the surface characterization techniques as applied to degraded spacer surfaces and discuss the possible degradation mechanisms.

New Short-Circuit Testing Facilities to Cope With the Recent Development of GIS

Short-circuit testing facilities are discussed for SF6 gas-insulated switchgear (GIS) equipment. It is shown that the supply voltage of 28kV will suffice to supply short-circuit current up to 80kA without severe distortions for four breaks used in the full voltage test of a tank-type SF6 gas circuit breaker (GCB). A new testing method using two transformers is proposed for a three-phase-in-one-tank-type GCB.

Ground Fault By Restriking Surge of SF6 Gas-Insulated Disconnecting Switch and Its Synthetic Tests

During a breaking operation of charging current with a disconnecting switch (DS) in SF6 gas-insulated switchgear (GIS), the occurrence of a fault to ground from the DS contact by a restriking surge was reported to be observed. The flashover voltage in this case, is appreciably lower than the normal withstand voltage to the ground. It has been clarified through high-speed photography with an image converter camera that the flashover is caused by a streamer generated during restriking between the DS contacts. In this respect, with the objective of confirming these phenomena in a simulated power system, two synthetic test circuits were constructed by using 550kV DS's. Verification tests were carried out to confirm the equivalence between these two test circuits. The DS's subjected to test withstood a surge voltage of 2.3pu-the maximum voltage obtained by simulating calculations of various GIS configurations.