과전류 인가 시 고온초전도 선재의 ?치 특성

임성우,최용선,황시돌,한병성 한국초전도학회 2003 Progress in superconductivity Vol.4 No.2

Voltage-current characteristics of High Temperature Superconductor(HTS) tapes after applying the current beyond their critical current was investigated. When over-current is applied, the current begins to flow through the metal sheath instead of superconductor. The HTS tapes quenched were analyzed using V-I curve with various magnitudes of current. Two kinds of tapes were compared with each other to examine the influence of critical current on quench development. As a result, it was found that the resistance of superconductors and joule heat due to the over-current affect current distribution in HTS tapes. Critical current of HTS tapes was considered as a main factor deciding over-current characteristics.

An Integrated Compensation Algorithm for PCC Voltage Fluctuation and Unbalance with Variable Limit of Positive and Negative Sequence Currents

Ji-Hoon Im,Seung-Ho Song,Sung-Min Cho 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.2

This paper proposes a point of common coupling (PCC) voltage compensation algorithm using a current limitation strategy for use in distributed generation (DG). The proposed strategy maintains the PCC voltage by prioritizing currents when an output current reference is larger than the current capacity of the power condition system (PCS) of the DG. With this strategy, the DG outputs the active current, reactive current, and the negative sequence current. The DG uses the reactive current for maintaining the PCC voltage within a normal range; the negative sequence current is used for reducing the PCC voltage unbalance. The proposed method was verified using PSIM simulation and experimental results.

돌출부를 지닌 전극의 전기도금시스템에 대한 이론적 이차 전류분포 해석

손태원,주재백,Sohn, Tai-Won,Ju, Jeh-Beck 한국전기화학회 2009 한국전기화학회지 Vol.12 No.4

돌출부를 지니고 있는 전극의 전기도금 공정에 대한 이론적 이차 전류분포에 대하여 고찰하였다. 전극이 모두 전도체인 경우(Case 1)와 돌출부위만 전도체인 경우(Case 2) 두 가지 경우에 대하여 인가전위, 이온교환 전류밀도와 용액의 비전도도의 비인 $\xi$값, aspect ratio의 영향 등에 대하여 살펴보았다. 그 결과 인가 전위와 $\xi$값이 증가할수록 전류분포는 불균등화가 심화됨을 알 수 있었다. Aspect ratio가 작아질수록 전류분포가 보다 균등화되며 Case 2의 경우가 Case 1의 경우 보다 균등도가 좋아짐을 알 수 있었다. 돌출부위가 다양한 모양으로 이루진 전극에 대해서도 이 모델을 적용한 결과 전극 표면에 따른 국부 전류분포를 동시에 계산할 수 있음을 알 수 있었고 이 경우에도 이전과 마찬가지로 $\xi$값이 감소할수록 전류분포의 균등도가 좋아짐을 알 수 있었다. Theoretical calculations for the secondary current distributions for the electrode with a projection part in electroplating were performed. Two kinds of electrodes were considered. One is a electrode with the overall conducting surfaces(Case 1) and the other is an electrode in which only a projection part has a conducting surface(Case 2). The effects of applied potential, the ratio of ion exchange current to conductivity, $\xi$ and the aspect ratio on the current distribution were examined. The increase of applied current or the value of $\xi$ decreased the uniformity of current distribution. The small value of aspect ratio resulted the more uniform current distribution and Case 2 showed the better uniformity than Case 2. When this model was applied into an electrode with various projection parts, the local current distribution along the electrode surface were obtained successfully. In this case, the decrease of $\xi$ also increase the uniformity of current distribution as seen previously.

Bus-voltage Sag Suppressing and Fault Current Limiting Characteristics of the SFCL Due to its Application Location in a Power Distribution System

Kim, Jin-Seok,Lim, Sung-Hun,Kim, Jae-Chul The Korean Institute of Electrical Engineers 2013 Journal of Electrical Engineering & Technology Vol.8 No.6

The application of the superconducting fault current limiter (SFCL) in a power distribution system is expected to contribute the voltage-sag suppression of the bus line as well as the fault-current reduction of the fault line. However, the application effects of the SFCL on the voltage sag of the bus line including the fault current are dependent on its application location in a power distribution system. In this paper, we investigated the fault current limiting and the voltage sag suppressing characteristics of the SFCL due to its application location such as the outgoing point of the feeder, the bus line, the neutral line and the 2nd side of the main transformer in a power distribution system, and analyzed the trace variations of the bus-voltage and fault-feeder current. The simulated power distribution system, which was composed of the universal power source, two transformers with the parallel connection and the impedance load banks connected with the 2nd side of the transformer through the power transmission lines, was constructed and the short-circuit tests for the constructed system were carried out. Through the analysis on the short-circuit tests for the simulated power distribution system with the SFCLs applied into its representative locations, the effects from the SFCL's application on the power distribution system were discussed from the viewpoints of both the suppression of the bus-voltage sag and the reduction of the fault current.

전류분포가 3본-도체의 임계전류/교류손실 특성에 미치는 영향

류경우,최병주 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.5

AC loss is an important issue in the design of high-T$\sub$c/ superconducting power cables which consist of a number of Bi-2223 tapes wound on a former. In the cables, the tapes have different critical currents intrinsically. And they are electrically connected to each other and current leads. These make loss measurements considerably complex, especially for short samples of laboratory size. So special cautions are required in the positioning of voltage leads for measuring the true loss voltage. In this work we have prepared a conductor composed of three Bi-2223 tapes with different critical currents. The critical current and AC loss characteristics in the conductor have experimentally investigated. The results show that for uniform current distributions the conductor's critical current is proportional to the critical current of the Bi-2223 tape to which a voltage lead is attached. However it depends on the current non-uniformity parameter in the conductor rather than the tape's critical currents for nonuniform current distributions. The loss tests indicate that the AC loss is dependent on arrangements of voltage leads but not on their contact positions. The measured losses in the conductor also agree well with the sum of the transport losses measured in each Bi-2223 tape.

Bus-voltage Sag Suppressing and Fault Current Limiting Characteristics of the SFCL Due to its Application Location in a Power Distribution System

김진석,임성훈,김재철 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.6

The application of the superconducting fault current limiter (SFCL) in a power distribution system is expected to contribute the voltage-sag suppression of the bus line as well as the fault-current reduction of the fault line. However, the application effects of the SFCL on the voltage sag of the bus line including the fault current are dependent on its application location in a power distribution system. In this paper, we investigated the fault current limiting and the voltage sag suppressing characteristics of the SFCL due to its application location such as the outgoing point of the feeder, the bus line, the neutral line and the 2nd side of the main transformer in a power distribution system, and analyzed the trace variations of the bus-voltage and fault-feeder current. The simulated power distribution system, which was composed of the universal power source, two transformers with the parallel connection and the impedance load banks connected with the 2nd side of the transformer through the power transmission lines, was constructed and the short-circuit tests for the constructed system were carried out. Through the analysis on the short-circuit tests for the simulated power distribution system with the SFCLs applied into its representative locations, the effects from the SFCL’s application on the power distribution system were discussed from the viewpoints of both the suppression of the bus-voltage sag and the reduction of the fault current.

Bus-voltage Sag Suppressing and Fault Current Limiting Characteristics of the SFCL Due to its Application Location in a Power Distribution System

Jin-Seok Kim,Sung-Hun Lim,Jae-Chul Kim 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.6

The application of the superconducting fault current limiter (SFCL) in a power distribution system is expected to contribute the voltage-sag suppression of the bus line as well as the fault-current reduction of the fault line. However, the application effects of the SFCL on the voltage sag of the bus line including the fault current are dependent on its application location in a power distribution system. In this paper, we investigated the fault current limiting and the voltage sag suppressing characteristics of the SFCL due to its application location such as the outgoing point of the feeder, the bus line, the neutral line and the 2nd side of the main transformer in a power distribution system, and analyzed the trace variations of the bus-voltage and fault-feeder current. The simulated power distribution system, which was composed of the universal power source, two transformers with the parallel connection and the impedance load banks connected with the 2nd side of the transformer through the power transmission lines, was constructed and the short-circuit tests for the constructed system were carried out. Through the analysis on the short-circuit tests for the simulated power distribution system with the SFCLs applied into its representative locations, the effects from the SFCL’s application on the power distribution system were discussed from the viewpoints of both the suppression of the bus-voltage sag and the reduction of the fault current.

Selective detection of AC transport current distributions in GdBCO coated conductors using low temperature scanning Hall probe microscopy

김찬,김무영,박희연,이형철 한국초전도.저온공학회 2017 한국초전도저온공학회논문지 Vol.19 No.1

We studied the distribution of the current density and its magnetic-field dependence in GdBCO coated conductors with AC biascurrents using low temperature scanning Hall probe microscopy. We selectively measured magnetic field profiles from AC signalobtained by Lock-in technique and calculated current distributions by inversion calculation. In order to confirm the ACmeasurement results, we applied DC current corresponding to RMS value of AC current and compared distribution of AC and DCtransport current. We carried out the same measurements at various external DC magnetic fields, and investigated field dependenceof AC current distribution. We notice that the AC current distribution unaffected by external magnetic fields and preserved theirown path on the contrary to DC current.

Selective detection of AC transport current distributions in GdBCO coated conductors using low temperature scanning Hall probe microscopy

Kim, Chan,Kim, Mu Young,Park, Hee Yeon,Ri, Hyeong-Ceoul The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.1

We studied the distribution of the current density and its magnetic-field dependence in GdBCO coated conductors with AC bias currents using low temperature scanning Hall probe microscopy. We selectively measured magnetic field profiles from AC signal obtained by Lock-in technique and calculated current distributions by inversion calculation. In order to confirm the AC measurement results, we applied DC current corresponding to RMS value of AC current and compared distribution of AC and DC transport current. We carried out the same measurements at various external DC magnetic fields, and investigated field dependence of AC current distribution. We notice that the AC current distribution unaffected by external magnetic fields and preserved their own path on the contrary to DC current.

Direct Individual-Phase Reactive Current Control Method for an Active Power-Line Conditioner in Three-Phase Four-Wire Distribution Feeders

Y. Sabi,Y. Yamada,T. Tanaka,F. Ikeda,M. Okamoto,S. R. Lee 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

This study proposes a new direct individual-phase reactive current control method that can suppress the neutral-line current for an active power-line conditioner in three-phase four-wire low-voltage distribution feeders. When the reactive currents are individually controlled with harmonics compensation, the sinusoidal and unbalanced source currents are obtained. This results in a large neutral-line current on the source side. This paper suggests the redistribution of the active components on the source side to suppress the large neutral-line current. The basic principle of the proposed active-component redistribution is discussed in detail and was confirmed by digital computer simulation. A laboratory-scale experimental setup was built and verified. Simulation and experimental results prove that the proposed direct individual-phase reactive current control method achieves sinusoidal and unbalanced source currents with the suppressed neutral-line current.