• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.194-196
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• 2000

This paper presents a new digital relaying algorithm for protection of a two winding power transformer. The proposed algorithm calculates mutual flux linkages of primary and secondary windings from the currents and voltages of primary and secondary windings. The mutual flux linkage ratio of primary and secondary windings is equal to the turn ratio in case of the steady state and magnetic inrush. On the other hand, the ratio is different from the turn ratio in case of internal winding faults. The algorithm does not require B-H curve. The results of various tests are satisfactory.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권1호
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• pp.17-21
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• 2005

AC loss is one of the important parameters in HTS (High Temperature Superconducting) AC devices. Among the HTS AC power devices, the transformer is the essential part in the electrical power system. But unfortunately, the transformer is the worst HTS device concerning AC loss because of very large magnetization loss due to high magnetic field applied to the HTS wire. We calculated the magnetization losses in HTS pancake windings for transformer according to the operating temperature. Two kinds of arrangement of HTS pancake windings were adopted for calculation of AC losses of a shell type transformer, and the analysis results were presented and discussed.

• 한국초전도ㆍ저온공학회논문지
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• 제19권2호
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• pp.44-47
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• 2017

In this paper, the current limiting characteristics of the transformer type superconducting fault current limiter (SFCL) with the two coupled secondary windings due to its winding direction were analyzed. To analyze the dependence of transient fault current limiting characteristics on the winding direction of the additional secondary winding, the fault current limiting tests of the SFCL with an additional secondary winding, wound as subtractive polarity winding and additive polarity winding, were carried out. The time interval of quench occurrence between two superconducting elements comprising the transformer type SFCL with the additional secondary winding was confirmed to be affected by the winding direction of the additional secondary winding. In case of the subtractive polarity winding of the additional secondary winding, the time interval of the quench occurrence in two superconducting elements was shorter than the case of the additive polarity winding.

• 대한전기학회논문지:전력기술부문A
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• 제53권7호
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• pp.375-381
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• 2004

This paper describes a three-winding transformer protective relaying algorithm based on the ratio of increments of flux linkages (RIFL). To minimize the approximation errors, the algorithm uses integration approximation. The RIFL of the two windings is equal to the turns ratio for all operating conditions except for an internal fault. For a single-phase and three-phase transformer containing the wye-connected windings, the increments of flux linkages (IFL) are calculated. For a three-phase transformer containing the delta-connected windings, the difference of IFL between the two phases are calculated to use the line currents, because the winding currents are practically unavailable. Their ratios are compared with the turns ratio. The comparative study between the proposed and differential approximation methods was conducted. The test results show that the algorithm can reduce the errors resulting from the conventional methods.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권11호
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• pp.572-576
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• 2006

As the increasing of capacity and technology of power facilities, rotating machines such as turbine generators and water turbines are getting higher at capacity but smaller in size. Thus the monitoring and diagnosis of generators for fault detection and protection has attracted intensive interest. Most of electrical faults of rotating machines appear in their windings. In case of an after-fault in high capacity rotating machines, the recovering cost is usually very expensive and additional time is necessary for returning in a normal situation. In this paper, the magnetic flux patterns in air-gap of a generator under various fault states as well as a normal state are simulated by a conventional FEM tool. These results are successfully applied to detection and diagnosis of the short-circuit condition in rotor windings of a high capacity generator.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1727-1729
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• 2001

Partial discharge testing are rapidly becoming the most powerful tool to assess the condition of high voltage generator and motor stator windings. Recently, on-line monitoring scheme with trending technique is widely applied in insulation diagnosis. This paper describes the on-line partial discharge detecting techniques in the high voltage motor stator windings. Also, on-line monitoring system for an insulation diagnosis are proposed.

• 한국초전도ㆍ저온공학회논문지
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• 제6권4호
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• pp.51-54
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• 2004

A 1 MV A single phase high temperature superconducting (HTS) transformer was manufactured. In order to reduce AC loss generated in the HTS winding, winding was concentrically arranged. Operation temperature is set at 65K to increase the critical current and reduce the amount of HTS tape usage and the volume. The cryogenic system which consists of main cryostat with the windings and secondary cryostat with 2 GM coolers and cryopump on top and heat exchanger inside is also designed and the cooling performance is simulated with Fluent. Temperature distribution of the windings is investigated whether the windings are kept under designed operation temperature.

• 한국초전도ㆍ저온공학회논문지
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• 제2권2호
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• pp.37-43
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• 2000

This paper describes the construction and test results of a 10kVA single phase HTS transformer. Double pancake windings with BSCCO-2223 HTS tape and G10-FRP cryostat with room temperature bore are used in the transformer. Two double pancake windings are connected in series to provide 188 turns and other two double pancake windings are connected in parallel to conduct the secondary current of 45.4[A]. Coefficients of the constructed transformer are obtained using the fundamental teats of the transformer. According to the test results, larger leakage reactance than expected is observed due to the bulky core which surrounds the sryostat.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1191-1192
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• 2015

To assess the deterioration condition of stator insulation, diagnostic and overpotential tests were performed on two high voltage(HV) motors for circulating water pump (CWP). Following the long term rewinding program, the diagnostic test was performed on two motors during the planning maintenance period. After completing the diagnostic test, overpotential test was done on the stator windings of HV motors. During the overpotential test, the No. 1 and No. 2 of HV motors failed at 8.8 kV and 7.9 kV, respectively. Stator windings of two HV motors had deteriorated significantly.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.493-497
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• 1998

In this paper, a three phase voltage source inverter synchronous motor drive is introduced which is capable of producing an approximate to sine-wave currents in the stator windings. Compare to a conventional current forced synchronous machine drive, for the same machine loss, a gain in out put per unit overall volume of 125% at a 50Hz supply frequency has been achieved. In addition, the torque pulsation has been drastically reduced. These improvements are achieved by introducing new rotor windings which are capable of controlling the stator current waveforms an approximate to sine-wave. A computer program has been developed which can be used to predict the dynamic performance of this drive/system. The paper describes the design of rotor windings for cylindrical rotor motor but the theory is equally applicable to salient-pole designs.