• 한국정밀공학회지
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• 제23권11호
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• pp.50-57
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• 2006

The water leak in water-cooled generator stator windings can generate the serious accidents such as insulation breakdown and it brings a generator to the unexpected sudden outage. Accordingly, it is important to diagnose the water absorption of them for the effective operation of power plant. Especially, the capacitance value which is measured for diagnosis is very small so the special diagnosis methods like stochastic theory are needed. KEPRI developed the water absorption test equipment and diagnosis technology for them. The developed diagnosis technology is applied to the real system and the results of water absorption test for stator windings are agreed to them of water leak test.

• 상하수도학회지
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• 제31권5호
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• pp.459-469
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• 2017

A real scale leakage test facility was developed to study the leak signal characteristics of water supply pipelines, and then leak tests were carried out. The facility was designed to overcome the limited experimental circumstances of domestic water supply pipeline experimental facilities. The length of the pipeline, which was installed as a straight line, is 280m. Six pipes were installed on a 70m interval with different pipe material and diameters that are DCIP(D200, D150, D100, D80), PE(D75) and PVC(D75).The intensity of the leakage is adjusted by changing the size of the leak hole and the opening rate of ball valve. Various pressure conditions were simulated using a pressure reducing valve.To minimize external noise sources which, deteriorate the quality of measured leak signal, the facility was built at a quiet area, where traffic and water consumption by customers is relatively rare. In addition, the usage of electric equipment was minimized to block out noise and the facility was operated using manual mode. From the experimental results of measured leakage signal at the facility, it was found that the signal intensity weakened and the signal of high frequency band attenuated as the distance from the water leakage point increased.

• Journal of Electrical Engineering and Technology
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• 제7권2호
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• pp.230-235
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• 2012

Cases of insulation breakdown damage of water-cooled generator stator windings occur frequently due to coolant leakage and water absorption worldwide. Such serious accidents may cause not only enormous economic loss but also very serious grid accidents in terms of stable supply of electric power. More than 50 % of domestic generators have been operated for more than 15 years, and leak and water absorption problem of windings are often found during the planned preventive maintenance period. Since 2005, leak and water absorption tests have been performed for total watercooled stator windings after fully drying the inside of the windings. The results are then comprehensively analyzed. The result of the test performed by GE, a foreign manufacturer, for 141 generators showed failures in 80 of them (failure rate: 57 %), whereas in the tests carried out in Korean domestic power plants, only 14 out of 50 generators showed failures (failure rate: 28 %).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3059-3066
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• 2008

It is reported that the life of generator stator windings is expected about 30 years and a leak and water absorption phenomena can be progressed by fatigue, vibration, and corrosion. The water-cooled generator stator windings which were operated over 15 years are over 20 units and the mechanical problems such as leak and water absorption were found in the generator stator windings. In this paper, the systematic mechanical integrity evaluation methods which are applied to the water-cooled generator stator windings within the country are introduced.

• Corrosion Science and Technology
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• 제3권6호
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• pp.233-239
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• 2004

Primary water stress corrosion cracking of steam generator tubings occur on many tubes in pressurized water reactors(PWRs), and they are repaired using sleeves or plugs. In order to develop proper repair criteria, it is necessary to know the leak behavior of the tubes, which have stress corrosion cracks. Crack development tests were carried out on the tubes at room temperature, and leak rate and burst pressure were measured on the degraded tubes at room temperature and a high temperature. No leakage was detected on the tubes where 100 % through wall crack developed, at 1560 psi, which is an operating pressure difference of pressurized water reactors(PWRs). In some tests, leak rates of the tubes increased with time at a constant internal water pressure. A test tube showed a very small amount of leakage at 2700 psi in a high temperature pressure test at $282^{\circ}C$, but it disappeared after the pressure increased slightly. Even cracks are 100 % through wall, they need to open in order to reach a certain amount of leak rate at the operating pressure difference.

• 공업화학
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• 제9권5호
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• pp.674-679
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• 1998

액체금속로 증기발생기 전열관 재질로 사용이 예상되는 ferrite steel 시편을 사용해서 소듐분위기에서 미량의 물 누출 실험을 수행하였다. 누출경로는 소듐-물 반응생성물 및 부식생성물에 의한 self-plugging 현상과 열적인 transient 및 전열관의 vibration에 의한 re-opening 메카니즘으로 설명이 가능하였다. 실험결과, 600 Psig의 injection 압력으로 5 g $H_2O$를 소듐분위기 속의 시편으로 누출시킨 경우, 누출초기와 약 70분 경과 후에 약간의 누출 흔적이 보였으나, self-plugging되었던 누출경로는 129분이 경과되자 완전 re-opening된 것으로 확인되었다. 누출시편의 re-opening shape은 2중으로 되어 있었으며, 소듐부위에서 시편 표면에 나타난 re-opening size 약 2 mm의 직경을 나타내었다.

• 공업화학
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• 제9권7호
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• pp.1023-1029
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• 1998

5Cr-1Mo steel을 이용하여 나트륨 분위기에서 미량 물 누출 실험을 수행하였다. 시편에서 미량 물 누출로 인한 누출경로의 완전 re-open time은 129분으로 나타났고, 그 크기는 직경 2mm를 나타냈다. 누출경로는 re-open되기 전에 누출부위를 중심으로 halos현상을 형성하였으며, halos의 크기와 실제 re-open크기와는 다르게 나타났다. 나트륨-물 반응으로 인한 재질의 부식은 나트륨부위로부터 시작되었으며, steam 부위에서는 부식이 발생하지 않았다. 시편 누출부위를 AES로 분석한 결과 Cr의 segregation이 가장 많이 나타났으며, SEM과 EPMA 관찰로부터 나트륨화합물들이 누출부위 주변에 대량 침적되어 있는 것이 관찰되어 나트륨 철 크롬혼합물 형태로 부식생성물들이 혼재되어 있는 것으로 예측되었다.

• 대한기계학회논문집B
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• 제34권2호
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• pp.137-143
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• 2010

발전기 고정자 권선 내부의 완전 건조는 누수시험을 위한 필요/충분조건이다. 발전기 운전에 의한 고주기 피로는 미세 균열 발생의 원인이 되고, 미세 균열에서의 물분자는 누설 진단의 신뢰성을 저하시킨다. 이와같은 이유로, 발전기 고정자 권선에 대한 누수시험에서 권선에 누설처가 있음에도 불구하고 누설이 없다는 결론과 같은 오류를 범하고 있다. 발전기 제작사는 누수시험을 고유한 건조 판정 기준을 제시하고 있지만, 실제로는 어떤 판정 기준도 누수시험을 위해 정확하게 건조 판정 기준을 지시하고 있지는 못하고 있는 실정이다. 그 이유는 발전기 고정자 권선의 복잡한 구조와 효과적인 건조 장비의 부재 때문이다. 본 논문에서는 수 냉각 발전기 고정자 권선의 내부 건조 여부를 판정하기 위한 건조 판정 기준을 완벽하게 제안하였으며 실험적으로 증명하였다.

• 상하수도학회지
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• 제30권3호
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• pp.313-319
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• 2016

In this study, the performance experiment was conducted to compare the permeate flux of hollow fiber Vacuum Membrane Distillation module according to leak problem between module housing and membrane bundle. For the permeate flux performance experiment of the two Vacuum Membrane Distillation modules, the Lab-scale experimental equipment was built in the capacity of $1m^3/day$. The performance test of the two Vacuum Membrane Distillation modules were analyzed according to the feed water conditions. As a result, it was analyzed that the leak VMD module decreased about 14% of permeate flux than normal VMD module.

• 대한기계학회논문집B
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• 제34권9호
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• pp.867-873
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• 2010

수냉각 발전기 고정자 권선에서의 냉각수 누수 및 흡습에 의한 절연파괴 손상사례가 국내 및 국외에서 자주 발생되고 있다. 이러한 사고는 막대한 경제적 피해뿐만 아니라 전력의 안정적 공급 측면에서 매우 심각한 계통 사고로 연결될 수 있다. 특히 국내 발전기는 15년 이상 운전되어 열화가 진행된 발전기가 50% 이상이며, 계획예방정비 기간 중에 권선에서의 누설 및 흡습 권선이 종종 발견되고 있다. 기존에는 누수 시험 전 과정인 권선 건조 과정을 무시한 채 누수 시험 결과만으로 권선 누설 여부를 진단하였으나 본 논문에서는 누수 시험을 위한 준비 단계인 진공 건조 시의 권선 내부의 진공도 패턴 분석을 통해 권선 누설 및 흡습 여부를 예측진단할 수 있는 방법을 실험적으로 증명하였다.