• 한국전기전자재료학회논문지
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• 제35권5호
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• pp.480-487
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• 2022

As a process to improve the insulation performance of VIs (Vacuum Interrupters), AC voltage conditioning is generally adopted by many manufacturers. Although the insulation performance is enhanced easily with AC Voltage conditioning, it has limitations when high recovery voltage is required due to high voltage rate or capacitive current switching. In particular, impurities such as oxides segregated on the electrode surface can be removed not by the energy level of the voltage conditioning but by the higher energy level achieved by the current conditioning process In this article, the current conditioning was carried out in various conditions and its validity was examined. The current conditioning was processed by changing the amplitude of applied current, arc time, the number of tests, and frequency. The insulation performance and the status of contact surface were checked as well. We concluded that as the applied charge quantity and the conditioning coverage area increase, the conditioning effect is much higher.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.134-138
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• 1994

According to request of insulating materials for high-voltage, recently we make effort not only to develop diagnostic skills of aging state but also to discover defects in insulating material in the early. Especially, partial discharge has been actively studied as a non-destructive diagnosis technique and very useful method. Because the method of partial discharge measurement has damages less than other conventional diagnosis technique. In this paper, the characteristics of partial discharge was investigated and studied on many samples with voids. In order to adapt as a practical diagnosis technique, it is studied on the characteristics of partial discharge and insulation breakdown in the high voltage. We suggest that partial discharge measurement can be used in order to diagnose defects in high-voltage insulation materials.

• 한국전기전자재료학회논문지
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• 제36권4호
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• pp.408-412
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• 2023

In this paper, in order to analyze high electrical insulation and cooling performance using mineral oil, the liquid insulating oil was changed in electrode shape and distance between electrodes to compare and analyze electrical characteristics according to equal electric field, quasi-equivalent electric field, and unequal electric field. As a result, the breakdown voltages were 36,875 V and 36,875 V in the form of sphere-sphere and plate-plate electrodes with equal electric fields. The breakdown voltage was 31,475 V in the sphere-plate electrode type, which is a quasi-equilibrium field, and the breakdown voltage was 28,592 V, 27,050 V, and 22,750 V in the needle-needle, sphere-needle, and needle-plate electrode types, which are unequal fields. Through this, it is possible to know the difference in breakdown voltage according to the type of electric field. The more equal the field, the higher the breakdown voltage, and the more unequal field, the lower the breakdown voltage. The difference in insulation breakdown voltage could be seen depending on the type of electric field, the insulation breakdown voltage was higher for the more equal electric field, and the insulation breakdown voltage was lower for the more unequal electric field. Also, it was confirmed that the closer the distance between the electrodes, the higher the insulation breakdown voltage, the higher the insulation breakdown current, and the insulation breakdown voltage and the insulation breakdown current were proportional.

• 한국전기전자재료학회논문지
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• 제25권4호
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• pp.309-314
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• 2012

To assess the condition of stator insulation, nondestructive and overpotential tests were performed on four high voltage motors. The stator windings under these tests have nominal ratings of 6.6 kV. After completing nondestructive tests, the AC overvoltage applied to the stator windings was gradually increasing until insulation failure in order to obtain the breakdown voltage. No. 1, No. 2, No. 3 and No. 4 of 6.6 kV motors failed near rated voltage of 18.4 kV, 19.8 kV, 19.7 kV and 21.7 kV, respectively. The breakdown voltage of four motors was higher that expected for good quality coils(14.2 kV) in 6.6 kV motors. Almost all of failures were located in a line-end coil at the exit from the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of AC current, dissipation factor($tan{\delta}$) and partial discharge magnitude.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 방전 플라즈마 유기절연재료 초전도 자성체연구회
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• pp.43-46
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• 2004

Recently many research activities on the diagnosis of stator winding insulation of high-voltage motors have been reported. Most of them utilize a trend analysis of partial discharges. In this paper, a novel on-line monitoring system for an insulation diagnosis is proposed. This system displays magnitude and phase angle distribution of partial discharge. The partial discharge activities can be interpreted more precisely by these techniques.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.216-217
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• 2006

A common problem in many fields of cryogenic power engineering is to apply high voltage to cold parts of superconducting equipment. In many of these cases a bushing provides electrical insulation for the conductor which makes the transition from ambient temperature to the cold environment. The cryogenic high voltage bushing for the 154kV, 100MVA high temperature superconducting(HTS) transformer is described. The bushing is energized with the line-to-ground voltage between the coaxial center and outer surrounding conductors, in the axial direction there is a temperature difference from ambient to about 77 K. For the insulation design of cryogenic bushing, the arrangement of condenser cone and electrical insulation characteristics of GFRP, Air, $LN_2$ and $GN_2$ were discussed in this paper.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.27-30
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• 2003

Recently, on power system, it is used to high voltage of transmission and distribution due to safe power supply and have high quality and insulation in order to satisfy excellent insulator. Thus, according to underground of high voltage cable, is occurred break down by ground short. Therefore, it is used to high quality XLPE power cable to interrupt instantaneous voltage drop. If it appear inner defect for cable whose have high quality and insulation, it is reduced rapidly due to concentration of electrical field. After assemble to manufacture, in order to inspect cable condition, it is decided much inspection standard. In this paper, In inner defect of assembling cable at manufacture, for measure the variation of insulation condition by void. it tested the variation of insulating characteristics, using $\phi$-q-n distribution variation in partial discharge experiment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.289-290
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• 2008

The purpose of this paper is to analyze AC Breakdown of solid/air composite insulation depending on the thickness and the pressure of dry air for eco-friendly insulation. SF6 gas has been widely used in electric equipment as gas insulation because of high dielectric strength and arc extinguishing performance. However, because SF6 gas is one of the green house effect gases, alternative insulation such as SF6 mixture, extremely low temperature gas, vacuum, liquid and solid insulating are being investigated.

• 전기학회논문지
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• 제61권10호
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• pp.1454-1460
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• 2012

In order to develop an new electric insulation material for heavy electric equipments, epoxy/micro/nano composite (EMNC) was prepared by mixing micro-silica with nano layered silicate, where the nano layered silicate was synthesized by our electric field dispersion method, EMNSC was prepared by treating the EMNC with a silane coupling agent. Thermal properties such as glass transition temperature (Tg) and thermal expansion coefficient, and DMA characteristics were studied, and mechanicla properties such as tensile and flexural tests were performed. AC electrical insulation strength was also tested. All properties of EMNSC were modified by treating EMNC with silane coupling agent and it was confirmed that our new developed composites could be used in the heavy electric equipments.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.226-227
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• 2007

Nanostructured materials are attracting increased interest and application. Exciting perspectives may be offered by electrical insulation. Epoxy/Organoclay nanocomposites may find new and upgraded applications in the electrical industry, replacing conventional insulation to provide improved performances in electric power apparatus, e.g, high voltage motor/generator stator winding insulation, dry mold transformer, etc. This paper shows that electrical and thermal properties of epoxy/organoclay nanocomposites insulating materials for dsc, dielectric constant, I-V characteristics, breakdown volatge, can improve significantly with respect to the basic, virgin materials.