Design of 1 MVA Single Phase HTS Transformer with Pancake Windings Cooled by Natural Convection of Sub-cooled Liquid Nitrogen

Kim, Woo-Seok,Kim, Sung-Hoon,Hahn, Song-yop,Park, Kyeong-Dal,Joo, Hyeong-Gil,Hong, Gye-Won,Han, Jin-Ho,Lee, Don-Kun,Park, Yeon-Suk The Korea Institute of Applied Superconductivity a 2003 한국초전도저온공학회논문지 Vol.5 No.3

A 1 MVA single-phase high temperature superconducting (HTS) transformer with BSCCO-2223 wire was designed in this paper. The rated voltages of each sides of the transformer are 22.9 kV and 6.6 kV respectively. Double pancake HTS windings arranged reciprocally will be used for the transformer windings, because of the advantages of insulation and distribution of surge voltage in case of a large power and high voltage transformer. Single HTS wire was used for the primary windings and four parallel wires were used for the secondary windings of the transformer with transposition. A core of the transformer was designed as a shell type core separated with the windings by a cryostat made of GFRP with a room temperature bore. The operating temperature of the HTS windings will be about 65K with sub-cooled liquid nitrogen. A cryogenic cooling system using a GM-cryocooler for this HTS transformer by natural convection of liquid nitrogen was designed. This type of cooling system can be a good option for compactness, efficiency, and reliability of the HTS transformer.

Partial Discharge Measurements of Artificial Defects in HTS Transformer Model using HFCT

Lee, S.H.,Shin, W.J.,Park, T.G.,Koo, J.Y.,Lee, B.W. The Korean Superconductivity Society 2009 Progress in superconductivity Vol.11 No.1

Partial discharge measurements in cryogenic dielectric materials of HTS transformer are very important because partial discharge was regarded as primary source for ageing and breakdown of cryogenic materials. But, partial discharge measurement techniques and its effects in low temperature high voltage environments were not suggested and there exist only a few reports on this research fields. Therefore, in order to implement reliable HTS transformers, partial discharge diagnosis techniques for cryogenic materials of HTS transformers were investigated using partial discharge (PD) pattern analysis methods. In this works, four different types of artificial defects including turn to turn insulation, free moving particle, void and protrusion, have been fabricated since it was commonly regarded that they might cause the sudden service failures of the power apparatus. For this purpose, these defects are installed into the dielectric materials in liquid nitrogen and experimental investigations have been carried out for the diagnosis of HTS transformer. And various PD patterns caused by the amount of quench of superconductors were analyzed. Throughout this works, the different PD patterns in cryogenic dielectric materials in liquid nitrogen, and PD measuring technique could be the fundamental steps to establish diagnosis technologies of HTS transformer for power applications.

Expected Future Market Volume of HTS Equipment in South Korea

Jae-young Yoon,Seung-ryul Lee,B. Yang,SeungYeup Lee,Youngjin Won 한국자기학회 2011 Journal of Magnetics Vol.16 No.2

This paper shows the entire future market volume of the HTS power industry, one of main smart grid equipment, in the case of the final market penetration ratio reaching 100% in the domestic market (South Korea). In this paper, the market penetration ratio is determined using the judgment method, with the market penetration S-curve induced using the Delphi method and the Product Life Cycle from 2011 (supposed launching year, not realistic physical year), to 2050 (expected final target year). This paper analyzes the HTS market penetration ratio of each stage, apparent innovation, early adapters, and the early/late majority and laggard stage, using the S-curve, thus calculating the total future market volume of HTS equipment in the positive sense. Finally, this paper estimates the quantitative analysis results for the HTS4-items (cable, FCL, transformer, rotation machine) of each year within the domestic market.

Partial Discharge Measurements of Artificial Defects in HTS Transformer Model using HFCT

S. H. Lee,W. J. Shin,T. G. Park,구자윤,이방욱 한국초전도학회 2009 Progress in superconductivity Vol.11 No.1

Partial discharge measurements in cryogenic dielectric materials of HTS transformer are very important because partial discharge was regarded as primary source for ageing and breakdown of cryogenic materials. But, partial discharge measurement techniques and its effects in low temperature high voltage environments were not suggested and there exist only a few reports on this research fields. Therefore, in order to implement reliable HTS transformers, partial discharge diagnosis techniques for cryogenic materials of HTS transformers were investigated using partial discharge (PD) pattern analysis methods. In this works, four different types of artificial defects including turn to turn insulation, free moving particle, void and protrusion, have been fabricated since it was commonly regarded that they might cause the sudden service failures of the power apparatus. For this purpose, these defects are installed into the dielectric materials in liquid nitrogen and experimental investigations have been carried out for the diagnosis of HTS transformer. And various PD patterns caused by the amount of quench of superconductors were analyzed. Throughout this works, the different PD patterns in cryogenic dielectric materials in liquid nitrogen, and PD measuring technique could be the fundamental steps to establish diagnosis technologies of HTS transformer for power applications

3상 10kVA 고온초전도변압기 특성해석

이희준,이승욱,차귀수 순천향대학교 부설 산업기술연구소 2002 순천향 산업기술연구소논문집 Vol.8 No.1

The high temperature superconductor transformers gain interests from the industries. This paper described construction and test results of 10kVA HTS transformer. Three phase transformer with double pancake windings were constructed. To reduce the leakage magnetic field, secondary coil were placed between the two primary coils. BSCCO-2223 wire, silicon sheet steel core and FRP cryostats were used to construct the transformer. A cryostat made of nonmagnetic and nonconducting material with a bore is going to be used in order to locate the core out of the cryostat. Three coils were stacked in one cryostat. Two double pancake coils were connected in series for the primary coil and on double pancak coil was used for the secondary coil. Total number of turns of the primary winding and the secondary winding were 112turns and 98turns, respectively. The rated voltages of each winding are 440/220V. The rated currents of each winding are 13.1/26.2A. After the test of basic properties of the 3 phase HTS transformer using no-load test, short-circuit test and full-load test, continuous operation of 100 hours with pure resistive load has been carried out. Test proved over-load capability and reliability of the HTS transformer.

Double Pancake Coil형 고온초전도 변압기의 전기적 절연 특성

백승명,정종만,이현수,한철수,김상현 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.2

High temperature superconductor can only be applied against an engineering specofication that has to be determined for each particular application form the design requirements for economic viability and for operation margins in service. However, in order to realize the HTS transformer, it is necessary to establish the high voltage insulation technique in cryogenic temperature. Therefore, the composite insulation of double pancake coil type transformer are described and AC breakdown voltage characteristics of liquid nitrogen(LN$_2$) under HTS pancake coil electrode made by Bi-2223/Ag are studied. The Breakdown of LN$_2$ is dominated electrode shape and distance. The influence of pressure on breakdown voltage is discussed with th different electrode. For the electrical insulation design of turn-to-turn insulation for the HTS transformer, we tested breakdown strength of insulation sheet under varying pressure. And we investigated surface flashover properties of LN$_2$ and complex conition of cryogenic gaseous nitrogen(CGN$_2$) obove a LN$_2$ surface. The surface voltage of GFRP was measured as a function of thickness and electrode distance in LN$_2$ and complex condition of CGN$_2$ above a LN$_2$ surface. this research presented information of electrical insulation design for double pancake coil(DPC) type HTS transformer.

Insulation design of HTS transformer with the use of continuous transposed conductor

Cheon, H.G.,Choi, J.H.,Choi, J.W.,Pang, M.S.,Kim, S.H. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.20

Important key technologies of a high-temperature superconducting (HTS) transformer may include the HTS wire technology, cooling, AC loss reduction, large current technology, and cryogenic temperature insulation. Among them, the cryogenic temperature insulation technology will be specifically a core technology for ensuring reliability for the smaller size, stability, economic efficiency of a HTS transformer. In this paper, we have simulated a HTS transformer applied with continuous transposed conductor, which has been studied as a way of reducing AC loss. Also, we analyzed the insulation composition and considered various characteristics of insulation breakdown in liquid nitrogen. Insulation design was realized in a way of calculating breakdown voltage of 0.1% with Weibull statistical treatment of the obtained experimental results and calculating insulation distance meeting basic impulse insulation level (BIL) 750kV, a target voltage.

Investigation of partial discharge phenomena in HTS transformer adopting different type of sensors

Koo, J.Y.,Lee, S.H.,Lee, Y.J.,Lee, B.W. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.20

In this work, we proposed the partial discharge diagnostic techniques to evaluate the cryogenic dielectric insulation of high temperature superconducting (HTS) transformers. Three kinds of different artificial defects were fabricated in order to evaluate partial discharge (PD) characteristics of HTS transformers. Various PD sensors were installed to evaluate the performance of PD detecting characteristics in liquid nitrogen. From the experiments, it was possible to analyze PD signals and to discriminate what kinds of defects exist in cryogenic liquids using various types of PD sensors. Among three PD sensors, AE sensor and HFCT sensor showed more stable performances compared to UHF sensor. But according to the characteristics of defects, three sensors showed different sensitivities according to the PD signal frequency bandwidth of artificial defects. Consequently, this PD measuring technique could be utilized to establish the diagnostic devices for HTS transformer.

10kVA 고온초전도 변압기 해석 및 제작

이희준,이승욱,차귀수 순천향대학교 부설 산업기술연구소 2001 순천향 산업기술연구소논문집 Vol.7 No.1

This paper presents the design and test results of a 10kVA single phase HTS transformer which is operating at 77K. Double pancake windings with BSCCO -2223 HTS tape and GFRP cryostat with room temperature bore are used in the transformer. Four double pan cake windings were used in total. Two double pancake windings are connected in series to provide 188 turns and other double pancake windings are connected in parallel to conduct the secondary current of 45.4A. The rated voltages of each winding are 440/220V. Numerical calculation using Finite Element Method was used to evaluate the performance of each arrangement. Considering the magnetizing reactance, leakage reactance, electrical insulation and the circulating current in low voltage winding which had two windings in parallel, HLLH arrangement was finally chosen. Estimation of the AC loss, magnetizing loss and self field loss, in the superconducting winding and the iron loss in the core were given. Magnetizing loss is calculated in the design stage, where effects of perpendicular field and parallel field are considered. Room temperature bore type cryostat has been constructed and its heat loss was measured. Coefficients of the constructed transformer are obtained using the fundamental tests of the transformer. According to the test results, larger leakage reactance than expected is observed due to the bulky core which surrounded the cryostat.

Iron Core Design of 3-Phase 40MVA HTS Power Transformer Considering Voltages per Turn

Lee, Chan-joo,Seok, Bok-yeol The Korean Institute of Electrical Engineers 2004 KIEE International Transactions on Electrical Mach Vol.b4 No.2

This paper presents the iron core design method of a high temperature superconducting (HTS) transformer considering voltages per turn (V/T). In this research, solenoid type HTS coils were selected for low voltage (LV) winding and double pancake coils for high voltage (HV) winding, just as in conventional large power transformers. V/T is one of the most fundamental elements used in designing transformers, as it decides the core cross sectional area and the number of primary and secondary winding turns. By controlling the V/T, the core dimension and core loss can be changed diversely. The leakage flux is another serious consideration in core design. The magnetic field perpendicular to the HTS wire causes its critical current to fall rapidly as the magnitude of the field increases slowly. Therefore in the design of iron core as well as superconducting windings, contemplation of leakage flux should be preceded. In this paper, the relationship between the V/T and core loss was observed and also, through computational calculations, the leakage magnetic fields perpendicular to the windings were found and their critical current decrement effects were considered in relation to the core design. The % impedance was calculated by way of the numerical method. Finally, various models were suggested.