• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권10호
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• pp.485-491
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• 2006

This paper describes that the distribution of electromagnetic field occurred by PD(Partial Discharge) pulse was calculated with simulation program and characteristics of calibration and PD pulses measured with folded dipole types sensors were analyzed. As the distribution of electromagnetic field in simulation was very random the wide band measuring methods were good. Therefore three folded dipole antenna types sensors which had different their widths were designed and made. The signal according to direction and distance between sensor and pulse source in these sensor was measured and the spectrum of surface PD were acquired in the experiment of model transformer. In this result the characteristics of sensor which had middle width was better than others and the main spectrum of PD signals in surface discharge were existed in around 220MHz, 320MHz and from 450MHz to 750MHz.

• 산업식품공학
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• 제15권4호
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• pp.398-403
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• 2011

비열살균기술로서 저온플라즈마 활용 가능성을 탐색하고자 유전체장벽 방전 플라즈마(DBDP)생성장치를 제작하여 최적 플라즈마생성 조건을 도출하고 Staphyloocus aureus를 대상으로 살균성능을 조사하였다. DBDP생성장치는 전력공급장치, 변압기, 전극, 시료처리부 등 네 부분으로 구성하였다. 인가전압은 단상 200 V AC를 사용하고, 변압기를 통하여 10.0-50.0 kV로 변환하고 10.0-50.0 kHz의 주파수의 펄스 구형파를 유전체인 세라믹 블록 내에 장치한 전극에 투입함으로써 상압에서 플라즈마를 생성하였다. 주파수를 올림에 따라 높은 전류가 유입되었고, 이에 비례하여 전력소비량이 증가하였다. 전류세기 1.0-2.0 A, 주파수32.0-35.3 kHz 범위에서 균일하고 안정적인 플라즈마 발생이 이루어졌으며 시료를 투입하지 않은 상태에서의 최적 전극간격은 1.85 mm 이었다. 전극간격을 높임에 따라 소비전력이 증가하였으나 시료 처리에 적합한 전극간격은 2.65 mm였다. DBDP 처리에 의한 온도상승은 최대 20$^{\circ}C$에 불과하여 열에 의한 생물학적 효과는 무시할 수 있었으며 따라서 비열기술임이 확인되었다. Staphyloocus aureus를 대상으로 DBDP 처리할 경우 초기 5분 동안은 살균치가 직선적인 증가를 보이다가 이후 다소 완만해지는 경향을 보였으며 1.25 A에서 10분간 처리 시 살균치는 5.0을 상회하였다.

• 전기학회논문지P
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• 제60권3호
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• pp.114-119
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• 2011

Large Power transformer is a complex and critical component of power plant and consists of cellulosic paper, insulation oil, core, coil etc. Insulation materials of transformer and related equipment break down to liberate dissolved gas due to corona, partial discharge, pyrolysis or thermal decomposition. The dissolved gas kinds can be related to the type of electrical faults, and the rate of gas generation can indicate the severity of the fault. The identities of gases being generated are using very useful to decide the condition of transformation status. Therefore dissolved gas analysis is one of the best condition monitoring methods for power transformer. Also, on-line multi-gas analyzer has been developed and installed to monitor the condition of critical transformers. Rogers method, IEC method, key gas method and Duval Triangle method are used to failure diagnosis typically, and those methods are using the ratio or kinds of dissolved gas to evaluate the condition of transformer. This paper analyzes the reliability of transformer diagnostic methods considering actual dissolved gas concentration. Fault diagnosis is performed based on the dissolved gas of five transformers which experienced various fault respectively in the field, and the diagnosis result is compared with the actual off-line fault analysis. In this comparison result, Diagnostic methods using dissolved gas ratio like Rogers method, IEC method are sometimes fall outside the ratio code and no diagnosis but Duval triangle method and Key gas method is correct comparatively.

• 전기학회논문지
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• 제60권6호
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• pp.1274-1279
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• 2011

The purpose of this paper is to present the manufacturing defect and damage pattern of a 3 phase 22.9/3.3kV oil immersed transformer, as well as to present an objective basis for the prevention of a similar accident and to secure data for the settlement of PL related disputes. It was found that in order to prevent the occurrence of accidents to transformers, insulating oil analysis, thermal image measurement, and corona discharge diagnosis, etc., were performed by establishing relevant regulation. The result of analysis performed on the external appearance of a transformer to which an accident occurred, the internal insulation resistance and protection system, etc., showed that most of the analysis items were judged to be acceptable. However, it was found that the insulation characteristics between the primary winding and the enclosure, those between the ground and the secondary winding, and those between the primary and secondary windings were inappropriate due to an insulating oil leak caused by damage to the pressure relief valve. From the analysis of the acidity values measured over the past 5 years, it is thought that an increase in carbon dioxide (CO2) caused an increase in the temperature inside the transformer and the increase in the ethylene gas increased the possibility of ignition. Even though 17 years have passed since the transformer was installed, it was found that the system's design, manufacture, maintenance and management have been performed well and the insulating paper was in good condition, and that there was no trace of public access or vandalism. However, in the case of transformers to which accidents have occurred, a melted area between the upper and the intermediate bobbins of the W-phase secondary winding as well as between its intermediate and lower bobbins. It can be seen that a V-pattern was formed at the carbonized area of the transformer and that the depth of the carbonization is deeper at the upper side than the lower side. In addition, it was found that physical bending and deformation occurred inside the secondary winding due to non-uniform pressure while performing transformer winding work. Therefore, since it is obvious that the accident occurred due to a manufacturing defect (winding work defect), it is thought that the manufacturer of the transformer is responsible for the accident and that it is lawful for the manufacture to investigate and prove the concrete cause of the accident according to the Product Liability Law (PLL).

• 한국산학기술학회논문지
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• 제22권2호
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• pp.810-818
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• 2021

ESS의 누설전류는 PCS(Power Control System)측 누설전류와 계통불평형 전류로 인한 누설전류로 구분되는데, PCS측의 누설전류는 정상 상태 운전 시, IGBT(Insulated Gate Bipolar Transistor) 스위칭의 전압 변화량과 IGBT와 방열판 사이에 존재하는 기생 커패시턴스에 의해 발생한다. 또한, 계통불평형 전류에 의한 누설전류는 불평형 부하로 인해 발생한 불평형 전류가 Yg-∆ 결선방식의 3각 철심이 적용된 태양광전원 연계형 변압기의 중성선을 통해 ESS로 유입된다. 따라서, 본 논문에서는 방열판 유도공식을 통해 산정한 기생 커패시턴스에 의하여 PCS측의 누설전류 발생 메커니즘을 제시하고 또한, 계통불평형에 의한 ESS측의 누설전류 발생 메커니즘을 제안한다. 이를 바탕으로, 배전계통 상용해석 프로그램인 PSCAD/EMTDC를 이용하여 배터리부, PCS부, AC전원부로 이루어진 PCS측의 누설전류 발생 메커니즘과 배전 계통부, 불평형 부하부, ESS부로 이루어진 계통불평형에 의한 ESS측의 누설전류 발생 메커니즘을 모델링하고, 누설전류의 특성을 평가한다. 상기의 모델링을 바탕으로 시뮬레이션을 수행한 결과, 외함의 저항과 접지저항의 크기에 따라 PCS측의 누설전류는 7[mA]에서 34[mA]로, 계통불평형에 의한 배터리 외함으로 흐르는 누설전류는 3.96[mA]에서 10.76[mA]로 증가하여 배터리측에 큰 영향을 미침을 알 수 있었다.