• Wind and Structures
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• 제27권5호
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• pp.325-336
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• 2018

The physical infrastructure of the power systems, including the high-voltage transmission towers and lines as well as the poles and wires for power distribution at a lower voltage level, is critical for the resilience of the community since the failures or nonfunctioning of these structures could introduce large area power outages under the extreme weather events. In the current engineering practices, single circuit lattice steel towers linked by transmission lines are widely used to form power transmission systems. After years of service and continues interactions with natural and built environment, progressive damages accumulate at various structural details and could gradually change the structural performance. This study is to evaluate the typical existing transmission tower-line system subjected to synoptic winds (atmospheric boundary layer winds). Effects from the possible corrosion penetration on the structural members of the transmission towers and the aerodynamic damping force on the conductors are evaluated. However, corrosion in connections is not included. Meanwhile, corrosion on the structural members is assumed to be evenly distributed. Wind loads are calculated based on the codes used for synoptic winds and the wind tunnel experiments were carried out to obtain the drag coefficients for different panels of the transmission towers as well as for the transmission lines. Sensitivity analysis is carried out based upon the incremental dynamic analysis (IDA) to evaluate the structural capacity of the transmission tower-line system for different corrosion and loading conditions. Meanwhile, extreme value analysis is also performed to further estimate the short-term extreme response of the transmission tower-line system.

• 센서학회지
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• 제30권5호
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• pp.342-348
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• 2021

For the characterization or failure analysis of electronic devices such as PCB (printed circuit boards), the most common method is the measurement of voltage waveforms with an oscilloscope. However, because there are many types of problems that cannot be detected by voltage waveform analysis, several other methods such as X-ray transmission, infrared imaging, or eddy current measurement have been applied for these analyses. However, these methods have also been limited to general analyses because they are partially useful in detecting physical defects, such as disconnections or short circuits. Fundamentally current waveform measurements during the operation of electronic devices need to be performed, however, commercially available current sensors have not yet been developed, particularly for applications in highly integrated PCB products with sub-millimeter fine pitch. In this study, we developed a highly sensitive PHR (planar hall resistance) magnetic sensor for application in highly integrated PCBs. The developed magnetic sensor exhibited sufficient features of an ultra-small size of less than 340 ㎛, magnetic field resolution of 10 nT, and current resolution of 1 mA, which can be applicable for PCB analyses. In this work, we introduce the development process of the magnetic sensing probe and its characteristic results in detail, and aim to extend this pin-type current probe to applications such as current distribution imaging of PCBs.

• 전기전자학회논문지
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• 제23권2호
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• pp.538-542
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• 2019

광 전환 효율에 관여하는 $TiO_2$와 같은 반도체 산화물은 염료 감응 태양전지(Dye-sensitized solar cell, DSSC)의 주요 요소이며, 효율을 개선하기 위해 서로 다른 반도체 산화물을 혼합하여 Pastes를 제조해 사용하는 연구가 이루어지고 있다. 본 연구에서는 $TiO_2-Nb_2O_5$ 혼합 반도체 산화물을 제조하여 염료 감응 태양전지의 특성을 분석하였다. 혼합 반도체 산화물이 광 전환 효율에 미치는 전기적인 특성을 분석하기 위해서 $Nb_2O_5$을 서로 다른 비율로 첨가하여 태양전지를 제작하였다. 이에 $Nb_2O_5$가 첨가됨에 따라 전해질과의 접촉에 의한 재결합 현상보다 전도성이 겅화되어 태양전지의 단락 전류, 개방전압, 변환 효율 등이 개선되는 것을 확인하였다.

• Current Photovoltaic Research
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• 제6권4호
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• pp.102-108
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• 2018

A glass-texturing technique was developed for photovoltaic (PV) module cover glass; periodic honeycomb textures were formed by using a conventional lithography technique and diluted hydrogen fluoride etching solutions. The etching conditions were optimized for three different types of textured structures. In contrast to a flat glass substrate, the textured glasses were structured with etched average surface angles of $31-57^{\circ}$, and large aspect ratios of 0.17-0.47; by using a finite difference time-domain simulation, we show that these textured surfaces increase the amount of scattered light and reduce reflectance on the glass surface. In addition, the optical transmittance of the textured glass was markedly improved by up to 95% for wavelengths ranging from 400 to 1100 nm. Furthermore, applying the textured structures to the cover glass of the PV module with heterojunction with intrinsic thin-layer crystalline silicon solar cells resulted in improvements in the short-circuit current density and module efficiency from 39 to $40.2mA/cm^2$ and from 21.65% to 22.41%, respectively. Considering these results, the proposed method has the potential to further strengthen the industrial and technical competitiveness of crystalline silicon solar cells.

• Current Photovoltaic Research
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• 제7권3호
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• pp.55-60
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• 2019

Polymer:nonfullerene solar cells with an inverted-type device structure were fabricated by employing the bulk heterojunction (BHJ) active layers, which are composed of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(6-methyl-2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-M). The BHJ layers were formed on a pre-patterned indium-tin oxide (ITO)-coated glass substrate by spin-coating using the blend solutions of PBDB-T and IT-M. The solar cell performances were investigated with respect to the cell position on the ITO-glass substrates. In addition, the short-term shelf lifetime of solar cells was tested by storing the PBDB-T:IT-M solar cells in a glovebox filled with inert gas. The results showed that the performance of solar cells was relatively higher for the cells close to the center of substrates, which was maintained even after storage for 24 h. In particular, the PCE of PBDB-T:IT-M solar cells was marginally decreased after storage for 24 h owing to the slightly reduced fill factor, even though the open circuit voltage was unchanged after 24 h.

• 전기전자학회논문지
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• 제23권1호
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• pp.330-333
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• 2019

실리콘 태양전지와 비교해 제조비용이 저렴하고 뛰어난 안정성을 가지고 있는 염료 감응 태양전지에 관한 다양한 연구가 지속적으로 이루어지고 있다. 본 연구에서는 $TiO_2$와 $Nb_2O_5$을 혼합하여 만든 반도체 산화물을 사용하여 염료 감응 태양전지의 특성을 연구하였다. $Nb_2O_5$을 서로 다른 비율로 첨가하여 태양전지를 제작하였고, 이에 따른 표면적, 전기적 특성을 측정하였다. $Nb_2O_5$가 첨가될수록 염료 및 전해질의 접촉 면적이 증가하게 되었고, 이에 따라 염료 감응 태양전지의 단락 전류, 개방전압, 곡선인자 및 변환 효율이 개선됨을 확인하였다.

• 한국전자통신학회논문지
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• 제16권4호
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• pp.643-652
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• 2021

송·배전시스템에서 사고나 장애는 결코 완벽하게 피할 수 없으며, 단락 및 지락사고는 계통운영자의 노력에도 불구하고 발생한다. 최근 대용량 신재생 분산전원의 송·배전계통에 연계가 급증하여 계통 운영에 다양한 영향을 주고 있어, 이를 최소화하기 위해 FRT(Fault-Ride-Through)와 같은 연계기준을 마련하여 풍력터빈 또는 태양광 인버터가 계통의 중대 장애 시 연계유지 또는 신속한 계통분리 등을 원활히 수행하여 운영자가 안정적으로 계통을 운영할 수 있도록 지원을 하여야 한다. 본 논문에서는 대표적인 신재생 분산전원의 계통연계 기준인 FRT 조건의 충족여부를 적절하게 판단하기 위하여 동기페이저 측정을 하는 PMU(Phasor Measurement Unit)를 사용한 검출 시스템을 설계 및 구축하고 발전기 탈락으로 인한 계통사고 사례를 기반으로 제시한 시스템을 분석하고 평가한다.

• 한국정보전자통신기술학회논문지
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• 제13권6호
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• pp.562-567
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• 2020

본 논문은 저장 탱크용 임시전력설비를 보호하기 위한 목적으로 특히 변압기를 감시하고 절연파괴 등과 같은 고장을 차단하고 보호하기 위한 보호계전기 정정에 관한 연구이다. 전력계통에 단락 또는 지락고장 등과 같은 이상이 발생하였을 때 이를 검출하여 고장이 발생한 기기 및 설비를 신속하게 차단하고 전력계통으로부터 분리하여 전력공급에 지장이 없도록 하여야 한다. 전력계통의 이상 상태를 빠르고 정확하게 감지할 수 있는 보호계전기의 정정이 중요하다. 또한 보호협조를 위해 고장종류와 고장의 원인을 정확히 적용한 고장전류 계산이 보호계전기 정정에 가장 중요한 요소이다. 저장 탱크용 임시전력설비 보호를 위해 적용하는 과전류계전기, 지락과전류계전기, 부족전압계전기, 지락과전압계전기 등이 보호협조가 가능하도록 보호계전기 정정 방법에 대해 연구하였다.

• 한국산학기술학회논문지
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• 제22권1호
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• pp.327-332
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• 2021

패키지레벨에서 반도체의 신뢰성 검사는 테스트 소켓에 반도체 칩 패키지를 탑재시킨 상태에서 테스트가 진행되며, 테스트 소켓은 기본적으로 반도체 칩 패키지의 형태에 따라서 그 모양이 결정되는 것이 일반적이다. 또한, 반도체 칩 패키지의 리드와 소켓 리드의 기계적인 접촉에 의해 테스트 장비와 연결하는 매개체의 역할을 하며, 신호전달 과정에서 신호의 손실을 최소화하여 반도체에 검사신호를 잘 전달할 수 있도록 하는 기능이 핵심이다. 본 연구에서는 이웃하고 있는 전기 전달 경로의 상호 영향성을 검사 할 수 있는 기술을 적용함으로써 수명 검사와 정밀 측정뿐만 아니라 이웃하고 있는 전기 전달 경로의 구조를 포함하여 단 한 번의 접촉을 통해 100개미만의 실리콘 테스트 소켓의 합선 테스트가 가능하도록 개발하였다. 개발된 장치의 테스트 결과 99%이상의 테스트 정밀도와 0.66이하의 동시 검사속도 특성을 나타내었다.

• 자동차안전학회지
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• 제13권2호
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• pp.30-34
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• 2021

Electrical failures and reliability problems of electronic components by ionic migration between adjacent device terminals have become an issue in automotive electronics. Especially unlike galvanic corrosion, ionic migration is occurred at high temperature and high humidity under applied electric field condition. Until now, although extensive studies of the ionic migrations dealing with PCBs, electrodes, and solders were reported, there is no study on the effect of insulation polymers and metallic fillers for ionic migration. In this research, therefore, ionic migration induced by the types and contents of polymers and metallic fillers, and variety conditions of temperature, humidity, and applied voltage was studied in detail. Ester and amide types of liquid crystal polymer (LCP) and poly (phthalamide) (PPA) were used as base polymers, respectively and compounded with the metallic fillers of Copper iodide (CuI), Zinc stearate (Zn-st), or Calcium stearate (Ca-st) in various compositions. The compounding polymers were fabricated in IPC-B-24 of SIR test coupon according to ISO 9455-17 with Cu electrodes for ionic migration test. While there is no change in LCP-based samples, ionic migration in PPA compounding sample with a high water absorption property was accelerated in the presence of 0.25 wt% or above of CuI at the environmental conditions of 85℃, 85% RH and 48V. The dendritic short-circuit growth of Cu caused by ionic migration between the electrodes on the surface of compounded polymers was systematically observed and analyzed by using optical microscopy and SEM (EDX).