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  • 2020-2024  (168)
  • 1
    Online Resource
    Online Resource
    Evaluation of Selection Criteria for the Level of Liquid Nitrogen in HTS Magnet System
    Institute of Electrical and Electronics Engineers (IEEE) ; 2022
    In:  IEEE Transactions on Applied Superconductivity Vol. 32, No. 6 ( 2022-9), p. 1-6
    Details
    In: IEEE Transactions on Applied Superconductivity, Institute of Electrical and Electronics Engineers (IEEE), Vol. 32, No. 6 ( 2022-9), p. 1-6
    Type of Medium: Online Resource
    ISSN: 1051-8223 , 1558-2515 , 2378-7074
    URL: Article
    DOI: 10.1109/TASC.2022.3162163
    Language: Unknown
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2022
    detail.hit.zdb_id: 2025387-4
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  • 2
    Online Resource
    Online Resource
    Real-Time Monitoring of the Vacuum Degree Based on the Partial Discharge and an Insulation Supplement Design for a Distribution Class Vacuum Interrupter
    MDPI AG ; 2021
    In:  Energies Vol. 14, No. 23 ( 2021-11-24), p. 7891-
    Details
    In: Energies, MDPI AG, Vol. 14, No. 23 ( 2021-11-24), p. 7891-
    Abstract: The internal pressure of a vacuum interrupter (VI) is increased by arc heat, ceramic cracking, gas leakage, and manufacturing defects. Accordingly, the dielectric strength of VI rapidly decreases. To improve the reliability of power transmission, efficient maintenance through the real-time monitoring of the vacuum degree is essential. However, real-time monitoring of the vacuum degree is difficult, and related research is scarce. Additionally, due to the insulation problems of this technology, there are few commercially available products. Therefore, this paper proposes a method for real-time monitoring of the vacuum degree and an insulation supplement design for a distribution class VI. First, dielectric experiments were conducted to identify the section in which the dielectric strength of the VI rapidly decreased according to the vacuum degree. Second, for real-time monitoring of the VI, several factors were proposed through the partial discharge in the VI, while the capacitance characteristics of the VI were calculated to improve the signal of the internal partial discharge. Finally, to supplement the dielectric problems of the solid insulation high voltage apparatus that occur when real-time monitoring technology is applied, the insulation supplement design was performed through the finite element method (FEM).
    Type of Medium: Online Resource
    ISSN: 1996-1073
    URL: Article
    DOI: 10.3390/en14237891
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2437446-5
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  • 3
    Online Resource
    Online Resource
    Comparison of AC and DC Partial Discharge by Monitoring of Vacuum Degree in a Distribution Class Vacuum Interrupter
    Institute of Electrical and Electronics Engineers (IEEE) ; 2022
    In:  IEEE Access Vol. 10 ( 2022), p. 36254-36267
    Details
    In: IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), Vol. 10 ( 2022), p. 36254-36267
    Type of Medium: Online Resource
    ISSN: 2169-3536
    URL: Article
    DOI: 10.1109/ACCESS.2022.3163448
    Language: Unknown
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2022
    detail.hit.zdb_id: 2687964-5
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  • 4
    Online Resource
    Online Resource
    Consideration of the Insulation Design Method on a ±200 kV Converter Valve Unit in an HVDC Converter Hall
    MDPI AG ; 2021
    In:  Energies Vol. 14, No. 8 ( 2021-04-19), p. 2296-
    Details
    In: Energies, MDPI AG, Vol. 14, No. 8 ( 2021-04-19), p. 2296-
    Abstract: A converter valve unit, which converts Alternating Current (AC) to Directing Current (DC) and DC to AC, is one of the key elements of high voltage direct current (HVDC) transmission. The insulation design of a converter valve unit should be considered for air clearance according to the DC superimposed overvoltage and the insulator that maintains the insulation performance and the corona shield to suppress DC corona discharge. There is no prescribed standard for the insulation design of a converter valve unit. Moreover, insulation performance under an applied DC voltage has not yet been thoroughly investigated. Therefore, it is necessary to study the insulation design method of the converter valve unit. In this paper, consideration of the insulation design method on a ±200 kV converter valve unit in an HVDC converter hall is performed. The finite element method (FEM) is used to simulate the 3D model. Additionally, the safety factor (SF) is applied in accordance with the dielectric test in IEC 62271-1. As a result, an insulation design process on the converter valve unit is proposed and the insulation design is carried through the design factors. It is confirmed that design factors on the air clearance, insulator and corona shield have a significant effect on a highly reliable insulation design.
    Type of Medium: Online Resource
    ISSN: 1996-1073
    URL: Article
    DOI: 10.3390/en14082296
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2437446-5
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  • 5
    Online Resource
    Online Resource
    Experimental and Simulation Studies on Stable Polarity Reversal in Aged HVDC Mass-Impregnated Cables
    MDPI AG ; 2024
    In:  Energies Vol. 17, No. 10 ( 2024-05-13), p. 2352-
    Details
    In: Energies, MDPI AG, Vol. 17, No. 10 ( 2024-05-13), p. 2352-
    Abstract: Mass-impregnated (MI) cables have been used for many years as cables in high-voltage direct current (HVDC) systems. In line commutated converter (LCC) HVDC systems, polarity reversal for power flow control can induce significant electrical stress on MI cables. Furthermore, the mass oil and kraft paper comprising the impregnated insulation have significantly different coefficients of thermal expansion. Load fluctuations in the cable lead to expansion and contraction of the mass, creating pressure within the insulation and causing redistribution of the impregnant. During this process, shrinkage cavities can form within the butt gaps. Since the dielectric strength of the cavities is lower than that of the surrounding impregnation, cavitation phenomena in impregnated paper insulation are considered a factor in degrading insulation performance. Consequently, this study analyzes the electrical conductivity of thermally aged materials and investigates the transient electric field characteristics within the cable. Additionally, it closely analyzes the formation and dissolution of cavities in MI cables during polarity reversal based on a numerical model of pressure behavior in porous media. The conductivity of the impregnated paper indicates that it has excellent resistance to thermal degradation. Simulation results for various load conditions highlight that the interval of load-off time and the magnitude of internal pressure significantly influence the cavitation phenomenon. Lastly, the study proposes stable system operation methods to prevent cavitation in MI cables.
    Type of Medium: Online Resource
    ISSN: 1996-1073
    URL: Article
    DOI: 10.3390/en17102352
    Language: English
    Publisher: MDPI AG
    Publication Date: 2024
    detail.hit.zdb_id: 2437446-5
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  • 6
    Online Resource
    Online Resource
    Development of Partial Discharge Analysis Model by Void in Solid Insulation Using Nonlinear Characteristics of Black-box Arc Model
    The Korean Institute of Electrical Engineers ; 2020
    In:  The transactions of The Korean Institute of Electrical Engineers Vol. 69, No. 11 ( 2020-11-30), p. 1707-1716
    Details
    In: The transactions of The Korean Institute of Electrical Engineers, The Korean Institute of Electrical Engineers, Vol. 69, No. 11 ( 2020-11-30), p. 1707-1716
    Type of Medium: Online Resource
    ISSN: 1975-8359 , 2287-4364
    Uniform Title: Black-box 아크 모델의 비선형 특성을 활용한 고체 절연물 내 보이드에 의한 부분방전 해석모델 개발
    URL: Article
    DOI: 10.5370/KIEE.2020.69.11.1707
    Language: English
    Publisher: The Korean Institute of Electrical Engineers
    Publication Date: 2020
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  • 7
    Online Resource
    Online Resource
    Numerical Analysis of Electric Field Characteristics and Interfacial Pressure of HVDC XLPE Cable Joint Considering Load Cycles
    MDPI AG ; 2022
    In:  Energies Vol. 15, No. 13 ( 2022-06-26), p. 4684-
    Details
    In: Energies, MDPI AG, Vol. 15, No. 13 ( 2022-06-26), p. 4684-
    Abstract: Recent innovations in HVDC extruded cable systems require the development of reliable and safe cable accessories. Cable accessories are made of several insulating materials and contain several interfaces. Interfaces made of different materials can cause electric field distortion and localized enhancement of the field. In addition, the internal temperature profiles of accessories differ depending on load conditions or installation environments, which may lead to an increase in or loss of interfacial pressure due to changes in the mechanical properties of materials. The loss of interfacial pressure degrades the contact state between materials. The micro voids formed due to pressure loss can cause partial discharge and tree, which in turn can lead to reduced lifespan and failure of the cable system. Therefore, it is necessary to study the electrical and mechanical characteristics of cable accessories considering various transient states. However, there is a limit to experimentally analyzing the actual structure. In this paper, electric field and mechanical stress for pre-molded cable joints were analyzed using an electrical model based on the conductivity of the material and a mechanical model based on elastic theory. Temperature fluctuations were simulated according to the sequence of the cable load cycle test, and time-varying electric fields and mechanical stresses were analyzed. From the simulation results, it was confirmed that the electric field and stress distribution in the joint continuously changed according to the heating and cooling periods. In addition, during the cooling cycle, the field strength at the interface near the conductor increased and the interface pressure decreased. In conclusion, it is important to ensure sufficient initial pressure so that the dielectric strength at the interface does not decrease even if there is a loss of interface pressure due to temperature fluctuations.
    Type of Medium: Online Resource
    ISSN: 1996-1073
    URL: Article
    DOI: 10.3390/en15134684
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2437446-5
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  • 8
    Online Resource
    Online Resource
    Classification of PRPD Pattern in Cast- Resin Transformers Using CNN and Implementation of Explainable AI (XAI) With Grad-CAM
    Institute of Electrical and Electronics Engineers (IEEE) ; 2024
    In:  IEEE Access Vol. 12 ( 2024), p. 53623-53632
    Details
    In: IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), Vol. 12 ( 2024), p. 53623-53632
    Type of Medium: Online Resource
    ISSN: 2169-3536
    URL: Article
    DOI: 10.1109/ACCESS.2024.3365135
    Language: Unknown
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2024
    detail.hit.zdb_id: 2687964-5
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  • 9
    Online Resource
    Online Resource
    Real-time fault detection system for large scale grid integrated solar photovoltaic power plants
    Elsevier BV ; 2021
    In:  International Journal of Electrical Power & Energy Systems Vol. 130 ( 2021-09), p. 106902-
    Details
    In: International Journal of Electrical Power & Energy Systems, Elsevier BV, Vol. 130 ( 2021-09), p. 106902-
    Type of Medium: Online Resource
    ISSN: 0142-0615
    URL: Article
    DOI: 10.1016/j.ijepes.2021.106902
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2021
    detail.hit.zdb_id: 2001425-9
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  • 10
    Online Resource
    Online Resource
    Calculation Method of Allowable Continuous Current for Direct Burial Laying HVDC Underground Cable
    MDPI AG ; 2021
    In:  Energies Vol. 14, No. 19 ( 2021-10-08), p. 6431-
    Details
    In: Energies, MDPI AG, Vol. 14, No. 19 ( 2021-10-08), p. 6431-
    Abstract: The calculation of the continuous allowable current of an underground cable is determined by various characteristics. To calculate the allowable current in cables with alternating magnetic fields such as AC, special phenomena such as the proximity effect and skin effect must be applied. However, there are no standards or research related to the calculation of the continuous allowable current of a DC power cable that does not have an alternating magnetic field. In this paper, a quantitative DC cable continuous allowable current calculation formula of direct burial laying was derived by applying the existing AC cable continuous allowable current calculation method to the DC system. We developed a calculation tool that can calculate the continuous allowable current of DC cables using the derived formula. Assuming the cable conditions (cable specification, laying conditions, soil characteristics, arrangement, and number of strands, etc.), a continuous allowable current simulation of DC cables was performed. In addition, the level of contribution to the continuous allowable current value was analyzed by classifying the parameter categories into major and minor factors in the order of influence on the allowable current among the determined calculated parameters. As a result, the effectiveness of the DC cable continuous allowable current calculation tool derived by performing the allowable current calculation simulation was evaluated, and the allowable current calculation method of the HVDC cable was established.
    Type of Medium: Online Resource
    ISSN: 1996-1073
    URL: Article
    DOI: 10.3390/en14196431
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2437446-5
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