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ESS 안전성 개선을 위한 결로 운전 조건 고려 고체절연물 연면 절연파괴특성 분석
김진태,이승용,김지영,석복렬,Kim, Jin-Tae,Lee, Seung-Yong,Kim, Ji-young,Seok, Bok Yeol 한국전력공사 2021 KEPCO Journal on electric power and energy Vol.7 No.2
As the large-scale renewable energy power plant increases, the high-capacity and compact Energy Storage System (ESS) is required. However, this trend could reduce the insulation reliability of ESS. In this study, the surface flashover characteristics for four types of solid insulators are investigated in the uniform electric field with AC and Lightning Impulse (LI) voltage waveforms under various contamination levels. In addtion, insulator surfaces are compared based on the contact angle before and after surface flashover. The experimental results show that AC flashover voltage is dependent on the materials and the contamination level, but LI flashover voltage is only associated with the contamination level. Especially, AC flashover voltage of PC (PolyCarbonate) is higher than that of other insulators, which is associated with the unique and sequential creepage discharge propagation pattern of PC. The localized discharges on the surface of PC form corresponding tracking points. Then, the interconnected trackings result in the complete flashover. This flashover patterns degrade the surface of PC much more than that of epoxy and Bulk Molding Compoud (BMC). Thus, the contact angle of PC is significantly reduced compared to that of other insulators. The increased hydrophilicity in the surface of PC enhances the insulator surface conductivity.
3차원 전기력선 추적 알고리즘을 이용한 변압기 절연안전율 평가
이찬주(Chanjoo Lee),석복렬(Bok-Yeol Seok),김동해(Dong-Hae Kim) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.10
변압기의 절연안전율은 전기력선 추적과정을 거쳐 전기력선의 길이와 그 경로에서의 평균전계를 계산하여 산출하는데, 변압기 제조사의 대부분은 2차원 전계해석을 기반으로 한 자체 절연안전율 평가 프로그램을 보유하고 있다. 그러나 변압기 내부 리드부 등 다수의 구조에서는 3차원 전계해석과 함께 3차원 공간에서의 전기력선 추적이 반드시 필요하다. 본 연구에서는 3차원 공간상 한 위치에서 전계의 크기와 방향을 계산한 후 그 방향을 따라 일정거리 떨어진 다음 위치를 구하는 방식의 3차원 전기력선 추적 알고리즘을 이용하여 최종적으로 절연안전율을 평가하는 기법을 개발하였다. 본 알고리즘은 VBS(Visual Basic Script)로 코딩하여 일반 상용 전자계해석 프로그램인 Maxwell과 연동되도록 구현하였다. 알고리즘의 타당성을 검증하기 위하여 축대청 구조인 고압권선과 저압권선 간에서의 절연안전율을 기존의 2차원 프로그램과 본 연구에서 개발된 3차원 프로그램을 활용하여 비교분석하였다. 그 결과, 전계와 전기력선 길이는 최대 4% 이내, 절연안전율은 약 1% 차이로 확인되었다. 본 연구에서 개발된 3차원 절연안전율 평가 프로그램은 변압기 내부의 대표적인 3차원 구조인 부싱-하우정, 리드-철심 등의 절연안전율 분석에 적용되었다.
배전급 초전도한류기 및 전력 IT 응용을 위한 실시간 모니터링 시스템 개발
朴東瑾(Dong-Keun Park),姜亨求(Hyoungku Kang),石福烈(Bok-Yeol Seok),高太國(Tae-Kuk Ko) 대한전기학회 2008 전기학회논문지 Vol.57 No.3
Recently, the development of superconducting fault current limiters (SFCLs) has been required as power demands increase in the power system. A distribution-level prototype resistive SFCL using coated conductor (CC) has been developed by Hyundai Heavy Industries Co., Ltd. and Yonsei University for the first time in the world. The ratings of the SFCL are 13.2 ㎸ / 630 A at normal operating condition. A novel non-inductive winding method is used in fabricating coils so there is almost zero impedance during normal operation. The distribution SFCL is cooled by sub-cooled liquid nitrogen (LN₂) of 65 K and 3 bar to enhance cryo-dielectric performance, critical current density, and thermal conductivity. In order to make reliable operation of an SFCL in real power systems, we monitored and controled its operation conditions by using supervisory control and data acquisition (SCADA) method. Thus, a monitoring system for the SFCL employing information technology (IT) is proposed and developed to be on the lookout for the operation conditions such as inside temperature, inside pressure, LN₂ level, voltage and current. Since operation temperature should be kept constant, bang-bang control for temperature feedback with a heater attached to the cold head of cryo-cooler is applied to the system. Short-circuit tests with prospective fault current of 10 ㎸ and AC dielectric withstand voltage tests up to 143 ㎸ for 1 minute were successfully performed at Korea Electrotechnology Research Institute. This paper deals with the development of a distribution level SFCL and its monitoring system for reliable operation.
고전압 전력기기 개발을 위한 기중 임펄스절연파괴특성에 관한 연구
강형구(Hyoungku Kang),김준연(Joon-Yeon Kim),석복렬(Bok-Yeol Seok),김동해(Dong-Hae Kim) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
To develop electrically reliable high voltage apparatuses, the experimental study on the electrical breakdown field strength is needed, as well as theoretical approach. In this paper, lightning impulse breakdown characteristics considering utilization factors are investigated for the establishment of insulation design criteria of an high voltage apparatus. The utilization factors are represented as the ratio of mean electric field to maximum electric field. Dielectric experiments are performed by using five kinds of sphere-plane electrode systems made of stainless steel. As a result, it is found that dielectric characteristics are affected by not only gap length but also utilization factor of electrode systems. The results are expected to be applicable to the design of high voltage apparatuses.