• 전기학회논문지
• /
• 제59권10호
• /
• pp.1856-1861
• /
• 2010

To reduce a high fault current, neutral ground reactors (NGR) were installed in the Korean substation. Current with several harmonic components flows in a NGR due to load unbalance in normal steady state and magnetic fields with several harmonic components are also generated around a NGR. As results of study, we found magnetic fields around a NGR in Korean substation included two harmonics, 180Hz and 540Hz. Magnetic fields of 180 Hz increased 3 times more current density inside a worker near a NGR than same magnitude magnetic fields of 60 Hz. We know a worker near a NGR may not meet ICNIRP guideline of 10(mA/$m^2$) due to several harmonic components.

• 한국식품조리과학회지
• /
• 제31권5호
• /
• pp.557-564
• /
• 2015

This study was performed to investigate the effect of Gastrodia elata extract on the quality characteristics of Non-glutinous rice porridge Jochung, saccharide by barley malt. Non-glutionous Rice Porridge Jochung with 0% (NGR1), 5% (NGR2), 10% (NGR3), 15% (NGR4) and 20% (NGR5) Gastrodia elata extract were produced. Moisture content and Solids content the interaction of two factors, the pH decreased with increasing Gastrodia elata extract concentration. Reducing sugar was significantly higher in groups containing Non-glutinous Rice Porridge Jochung (NGR) with Gastrodia elata extract added than the control group, especially the 15% NGR4 addition group with $1.22{\pm}0.02g/L$. Free acidity contents were 27.27 meq/kg control and 29.67~41.03 meq/kg among the samples with p<0.001. There were significant levels of total phenolics and TEAC found for the antioxidant activity of the Jochung samples with Gastrodia elata extract added. Increasing the ratio of Gastrodia elata Extract in Jochung tended to decrease color value. The results showed that Jochung containng less than 15% Gastrodia elata Extract gave the highest scores in quality characteristics and sensory evaluation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 하계학술대회 논문집 A
• /
• pp.480-482
• /
• 2004

This paper presents a study on the NGR problem for harmonic in distribution systems. Overheating of NGR (Neutral Ground reactor), by neutral current in distribution system, is important cause of transformer breakdown of substation. Countermeasures about zero-sequence component harmonic in neutral line are required.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 추계학술대회 논문집 전기설비전문위원
• /
• pp.83-88
• /
• 2004

As the electric system is getting larger to meet the increasing demand for electric power, the rating of power apparatus is becoming inevitably higher in its working voltage and larger in its capacity. According to KEPCO reports, power transformers in the KEPCO system have undergone troubles such as winding short insulation breakdowns every year since 1981. the cause of this troubles were high one line grounding fault currents in KEPCO systems that had direct grounding systems. KEPCO has installed the NGR(neutral grounding reactor) to lower this fault current and reduced winding short insulation breakdowns in power transformers. But when a circuit breaker opened a no load bus, some trips of circuit breakers for protecting transformer have occurred by mal-operation of 59GT(overvoltage ground relay) that detect disconnection of NGR. Therefore, in this paper, we analyzed the cause and examined the effect of time delav circuit to prevent wrong operation of 59GT.

• 한국식품저장유통학회지
• /
• 제30권3호
• /
• pp.419-433
• /
• 2023

Dried apple bugak, a traditional Korean dried food, was made using superfine powders of glutinous rice (GR), non-glutinous rice (NGR), and Wasabia koreana Nakai leaf (WKNL) as coating materials. This study aimed to determine the effect of coating sliced apples with superfine GR powders substitute with superfine NGR and WKNL powders at different ratios. Apple slices coated with superfine GR, NGR and WKNL powders were air-fried and compared with dried and air-fried apple bugak coated with superfine GR powders. The results showed that coating apple slices with superfine GR powders with the addition of superfine NGR and WKNL powders significantly increased oil absorption capacity and antioxidant activity but reduced viscosity, water absorption capacity, total polyphenol, total flavonoids contents, and improved color and structural improvements. Among all the samples, 80:20:5-treated (GR:NGR:WKNL) dried and air-fried bugak showed enhanced quality characteristics. Thus, the results suggested that coating apple slices by the substituting GR superfine rice powders with 10 or 20% of NGR and 3 or 5% of WKNL superfine powders produces good quality dried and air-fried bugak with nutritious characteristics.

• 한국환경생태학회:학술대회논문집
• /
• 한국환경생태학회 2003년도 추계학술논문발표회 논문집
• /
• pp.172-174
• /
• 2003

• 전기학회논문지
• /
• 제58권10호
• /
• pp.1916-1922
• /
• 2009

Introducing distributed generators(DGs) to utility distribution system can cause malfunction of relay on the grid when ground faults or severe load unbalances are occurred on the system. Because DGs interconnected to the grid can contribute fault currents and make bidirectional power flows on the system, fault currents from DGs can cause an interference of relay operation. A directional over current relay(DOCR) can determine the direction of power flow whether a fault occurs at the source side or load side through detecting the phases of voltage and current simultaneously. However, it is identified in this paper that the contributed fault current(Ifdg) from the ground source when was occurred to contribute single-line-to-ground(SLG) fault current, has various phases according to the distances from the ground source. It means that the directionality of Ifdg may not be determined by simply detecting the phases of voltage and current in some fault conditions. The magnitude of Ifdg can be estimated approximately as high as 3 times of a phase current and its maximum is up to 2,000 A depending on the capacity of generation facilities. In order to prevent malfunction of relay and damage of DG facilities from the contribution of ground fault currents, Ifdg should be limited within a proper range. Installation of neutral ground reactor (NGR) at a primary neutral of interconnection transformer was suggested in the paper. Capacity of the proposed NGR can be adjusted easily by controlling taps of the NGR. An algorithm for unidirectional relay was also proposed to prevent the malfunction of relay due to the fault current, Ifdg. By the algorithm, it is possible to determine the directionality of fault from measuring only the magnitude of fault current. It also implies that the directionality of fault can be detected by unidirectional relay without replacement of relay with the bidirectional relay.

• 전기학회논문지P
• /
• 제57권3호
• /
• pp.302-310
• /
• 2008

In order to evaluate the nominal rating of breakers in distribution system due to the increased capacity and operating conditions of power transformers in 154 kV substation, the fault currents in distribution system were calculated by the conventional method and simulations of PSCAD/EMTDC program. Consequently, under the condition of the parallel operation of transformers, the fault currents exceed the nominal current of the breakers in some areas. Without NGR at the secondary neutral of the transformer, the current of single line-to-ground fault was bigger than that of 3-phase fault. Therefore, the results clearly show that the measures to limit the fault currents in distribution system are needed when the increased capacity of power transformers is introduced into 154 kV substation.

• 한국전자통신학회논문지
• /
• 제6권2호
• /
• pp.262-267
• /
• 2011

본 연구에서 동부산S/S #3M.Tr 및 부민S/S #1,2M.Tr의 중성선에 설치 사용 중인 NGR 과열원인을 분석하고 해소방안을 제시하여 안정적 전력공급에 이바지하고자한다. 전력계통에 사용 중인 변압기 중성점 접지리액터는 1선지락 고장시 변압기에 유입되는 지락고장전류의 크기를 제한하여 변압기 고장을 감소시키는 역할을 하며 가공절연전선의 용융단선고장방지 일단접지변압기 폭발가능성방지 차단기 차단용량감소 등에 기여하는 설비로 고장발생시 전력계통운용에 막대한 지장을 초래할 수 있다. 따라서 전력계통에 설치 운전 중인 동부산S/S #3M.Tr 중성점 접지리액터 TOP&BOTTOM BRACE부의 온도 상승원인분석과 부민S/S 중성점 접지리액터에 흐르는 과전류로 인한 과열원인 분석을 하였다.

• Asian-Australasian Journal of Animal Sciences
• /
• 제17권5호
• /
• pp.693-699
• /
• 2004

Live animal selection programs that favor animals with a minimum amount of carcass fat are used for improving breeding flocks of sheep. To predict carcass characteristics of live sheep using body measurements in breeding flocks, 200 male and female lambs of two fat-tailed Iranian sheep breeds (Moghani and Makui) were used. Depth of soft tissue over the 12th rib of the live animals was measured with ultrasound (ULGR) and with hypodermic needle (NGR). The height at withers (HW), body length (BL), circumference of heart girth (CH) and width of hooks (WH), were measured. All animals were slaughtered; carcasses were cut into joints and dissected. Breed had a significant effect on all of the live easurements. The Moghani breed showed a higher value for HW, CH, ULGR and NGR, compared to that of Makui. Except for soft tissue depths; ULGR, NGR and GR, the male lambs showed higher values in live and carcass measurements than females. Percentages of carcass, total fat and intermuscular fat in females were higher than that of male lambs. In spite of the higher amount of subcutaneous and intermuscular fat in female (which is usually used for their physiological need, such as pregnancy and lactation), the male lambs had a heavier fat-tail than females. There was a wide range of variation of percentage of total carcass fat and total chemical fat content of carcass in the two breeds. Eventually this wide variation could be use by animal breeders for selection of animals with a lesser amount of carcass fat. Live weight of lambs showed a relatively low correlation with percentage of carcass lean, total fat and subcutaneous and intermuscular fat. Total lean meat was predicted with relatively high coefficients of determination in the two breeds ($R^2$=0.61 and 0.89, respectively). Live weight and carcass traits were predicted using simple measurements, but with $R^2$ ranging from 0.53 to 0.93.