Analysis of Response of a Wind Farm during Grid/Inter-tie Fault Conditions

Lee, Hye-Won,Kim, Yeon-Hee,Zheng, Tai-Ying,Lee, Sang-Cheol,Kang, Yong-Cheol 대한전기학회 2012 The Journal of International Council on Electrical Vol.2 No.3

A wind farm consists of a large number of small wind turbine generators (WTGs) whilst a thermal power plant consists of a small number of large generators. To maintain high quality and high reliability of electrical energy, the wind farm should have the same performance as the thermal power plant in the transient state as well as in the steady state. The wind farm shows similar performance to the conventional power plant in the steady state due to the advanced control technologies. However, it shows quite different characteristics during fault conditions in a grid or at an inter-tie. This gives significant effects on both the operation of a wind farm and the power system stability. This paper describes an analysis of response of a wind farm during grid/inter-tie fault conditions. During fault conditions, each WTG might produce different frequencies in the voltage. These result in the non-fundamental frequencies in the voltage and the current of a point of common coupling, which is called by "beats". This phenomenon requires careful attention on control technologies of a WTG to improve the characteristics in the transient state such as a fault ride-through requirement. Moreover, it may cause difficulties in protection relays of a wind farm. The response of a wind farm for various fault and wind conditions of each WTG was analyzed using a PSCAD/EMTDC simulator.

그리드/연계선 사고 시 풍력발전단지의 응동 분석

이혜원(Hye-Won Lee),김연희(Yeon-Hee Kim),정태영(Tai-Ying Zheng),이상철(Sang-Cheol Lee),강용철(Yong-Cheol Kang) 대한전기학회 2011 전기학회논문지 Vol.60 No.6

In a wind farm, a large number of small wind turbine generators (WTGs) operate whilst a small number of a large generator do in a conventional power plant. To maintain high quality and reliability of electrical energy, a wind farm should have equal performance to a thermal power plant in the transient state as well as in the steady state. The wind farm shows similar performance to the conventional power plant in the steady state due to the advanced control technologies. However, it shows quite different characteristics during fault conditions in a grid, which gives significant effects on the operation of a wind farm and the power system stability. This paper presents an analysis of response of a wind farm during grid fault conditions. During fault conditions, each WTG might produce different frequency components in the voltage. The different frequency components result in the non-fundamental frequencies in the voltage and the current of a wind farm, which is called by “beats”. This phenomenon requires considerable changes of control technologies of a WTG to improve the characteristics in the transient state such as a fault ride-through requirement of a wind farm. Moreover, it may cause difficulties in protection relays of a wind farm. This paper analyzes the response of a wind farm for various fault conditions using a PSCAD/EMTDC simulator.

아미노 요시히코의 일본론에 대한 재검토 - 중세사의 관점에서 -

南基鶴(Nam, Ki Hak) 일본사학회 2004 일본역사연구 Vol.19 No.-

Amino s understanding of the Japanese emperor seems to be suprahistorical and mystical in the sense that the religiosity and ideal sanctity of the emperor are emphasized. Non-farming people suggested by him as the social foundation of the emperor cannot be distinguished as a group from the farmers. They were hardly related to the emperor or Buddhist and Shinto deities. Amino s argument to regard the Kamakura bakufu as the eastern state which stood side by side with the western state centered around Kyoto is based on the assumption that regional diversity led to the ethnic diversity and political power based on the locality was the state power. His argument cannot be accepted from the fact that the bakufu itself recognized the emperor as a king of the state. Lastly, Amino s new view of the sea is not free from criticism. It is true that the seas which surrounded the Japanese islands provided the Japanese with a place to communicate with other Asian people, and stimulated by these cultural exchanges various local cultures flourished in the islands. However, it is undeniable that societies developed around the islands remained relatively isolated and backward compared to other societies developed in the Korean peninsular or the Chinese continent. Amino s discourse seems to aim at the orientation of national Japanese history nation in addition to his explicit orientation toward people s social history in the Japanese islands.

1910년대 초반 석장둔 인근 간척지 소유 양상

김한빛 서울대학교 인문학연구원 2024 인문논총(人文論叢) Vol.81 No.3

이 글은 현재 시흥시 관내에 있는 소위 석장둔 인근 간척지의 1910년대 소유 상황을 살펴보고자 한다. 이를 통해 간척지에서 토지 소유가 소수 지주에게 집중되는 모습과 비옥도와 토지 소유 상태의 관계를 살펴보고자 한다. 석장둔 인근 간척지는 바다와 구릉에 둘러싸여 있고 경작지 대부분이 논으로 조성되어 있으며 관련 자료가 풍부하여 1910년대 소유 상황을 확인하기에 용이하였다. 해당 지역 토지의 과세가격과 비옥도는 상관관계를 갖는 것으로 파악되었다. 그리고 서울에 사는 부재지주가 면적 기준 간척지 내 토지 과반을 소유하고 있었다. 토지 소유는 소수에게 집중되어 있었으며, 특히 당대 권력자인 순헌황귀비 엄씨는 영역 내 가장 많은 토지를 소유함과 동시에 다른 지주들보다 비옥한 땅을 가지고 있었다. 간척지가 아닌 인근 지역과 소유 양상을 비교해 볼 때, 이와 같이 토지 소유가 소수 지주에게 집중되는 현상은 석장둔 인근 간척지의 독특한 현상으로 여겨진다. This article aims to examine the ownership situation of the so-called reclaimed land around the Seokjang State Farm within Siheung City during the 1910s. Through this work, the concentration of land ownership among a few landlords and the relationship between soil fertility and land ownership status will be analyzed. The reclaimed land around the Seokjang State Farm is surrounded by the sea and hills, with most of the cultivated land being rice paddies. The abundance of related materials made it easy to verify the ownership situation in the 1910s. It was found that the taxation value of the land and its fertility had a correlation. Moreover, absentee landlords living in Seoul owned more than half of the reclaimed land area. Land ownership was concentrated among a few individuals, especially the Imperial Noble Consort Sunheon, who was a powerful figure at the time, owning the largest amount of land in the area, which was also more fertile compared to other landlords. When compared with the ownership patterns of neighboring areas that are not reclaimed land, this concentration of land ownership among a few landlords appears to be a unique phenomenon in the reclaimed land around the Seokjang State Farm.

조선후기 영도의 공간적 특성과 경관의 조성

양흥숙(Yang, Heung-Sook) 부산대학교 한국민족문화연구소 2015 한국민족문화 Vol.57 No.-

영도는 부산광역시 내에서 육지와 200여 미터 떨어진 가까운 유인도이고 하나의 자치구를 이루고 있다. 근대 이후 공업화가 진행되면서 인구 밀집지역이 되었고 관련 연구성과도 나왔지만, 근대 이전 특히 조선시대의 영도에 대해서는 별로 연구가 이루어지지 못하였다. 국영 목장, 봉산으로 사용되는 곳이었기 때문에 사람들과의 관계가 없는 곳으로 여겨졌기 때문이다. 그러나 사람들과는 무관하게 존재한 것처럼 보였던 ‘섬’ 영도는 실제로는 (육지) 사람의 생활 공간으로 존재하였다. 부산항의 가장 바깥 경계에 위치하면서 부산의 길목이 되기도 하고, 부산항을 해양으로부터 지켜주는 공간이 되기도 하였다. 이런 인식은 古地圖에 나타나기도 하고 여러 고문헌 속에 기록되면서, 사람들과 무관한 것이 아니라 사람들의 기억에 자리할 수 있었다. 국영 목장, 봉산으로 존재한 영도는 차단된, 금지된 공간이 아니라, 이를 운영하기 위한 사람들이 있어야 하는 공간이었고, 사람들이 있으면서 사당(제사 공간)이 생기는 등 상징적인 공간이 될 수 있었다. 또한 육지와 가까웠기 때문에 영도와 마주보는 육지 공간, 즉 일본인 마을인 왜관과 가장 가까웠다. 특히 조선에 온 일본인들은 모두 대마도인들로 대마도와 섬이라는 같은 지형을 가진 영도에 대해 친숙하게 여기고 있었다. 왜관을 그리는 그림에도 영도가 등장하고 그들의 사당도 있는 공간이었다. 영도는 섬이라고 하여 육지와 동떨어진 곳이 아니라, 끊임없이 사람들과의 관계 속에서 존재하였다. 나아가 사람들에게는 경험이 이루어지고 기억이 되는 공간으로 의미를 쌓아가고 있었다. Yeongdo is an inhabited island in the Busan Metropolitan City. Located 200m off the shore, it is made up of a borough. Since the modern times, it became a densely populated area with the progress of industrialization. However, little has been studied about the island before the modern era, and especially during the Joseon Dynasty. This is because the island had been used as a state-operated farm and a prohibited forest, and thereby was regarded unrelated to the general public. This study investigates how Yeongdo, which appeared to have existed unrelated to Busan people, actually existed building its significance in relation to the lives of people. Located at the farthest boundary of Busan port, Yeongdo has been a strategic point of Busan, an important space that protected the Busan port from the field of ocean. This recognition is indicated in old maps and many other ancient documents, suggesting that, rather being unrelated to the people, the island came to hold a place in their memory. Yeongdo, which had existed as a state-operated farm and a prohibited forest, was actually neither a blocked nor prohibited place, but was a place that required people to operate and manage the farm and forest. With the habitation of people, shrines for ancestrial rites appeared in Yeongdo. Thus, the island became a symbolic space. In addition, since Yeongdo was close to the land, it was the closest place to Waegwan, the Japanese residence located on the shore facing the island. Most of the Japanese people who came to Joseon were from Tsushima, and thus felt familiar with the Yeongdo, which had topographical features of an island like Tsushima. In their drawings of Waegwan, the included Yeongdo, as a space with their shrine. Yeongdo, despite its topographic features as an island, was not disconnected from the land but rather existed in constant relationship with the people. Furthermore, it had been building its significance as a place, where people had experiences, a space to remember.

Occurrence and seasonal variation of organochlorine pesticides in selected vegetable farmlands in Lagos State, Nigeria

Fidelia Ijeoma Osuala,Olamide Florence Humphrey,Miriam Nwana Igwo-Ezikpe,Arnold Godfrey Udoh,Iyanuoluwa Adegbuyi,Mojeed Fasasi,Precious Agada,Azeemah Jimoh,Olufunke Okubamowo 환경독성보건학회 2024 환경독성보건학회지 Vol.39 No.2

Pest infestation in crop production have increased farmers interest in pesticides use with short and long term consequences. This study investigated the occurrence and seasonal variations of organochlorine pesticide residues in vegetable farms in selected areas of Lagos State. Non carcinogenic and carcinogenic risk assessment was also evaluated. Soil samples were collected during the wet and dry seasons at soil depth of 0-30 cm. Gas chromatography coupled with an Agilent mass spectrometer was used to analyse organochlorine residues (alpha-lindane,lindane, delta.-lindane, aldrin, heptachlor epoxide, alpha.-endosulfan, p,p-dichlorodiphenyldichloroethylene (p,p-DDE), endrin, endosulfan, m,p-dichlorodiphenyldichloroethane (m,p-DDD), endosulfan sulfate, o,p-dichlorodiphenyltrichloroethane (o,p-DDT) and endrin ketone) in soil. Heptachlor epoxide showed maximum concentration of 43.03 mg/kg in Station 19 in Western zone during the dry season while m,p-DDD and endosulfan had minimum value of 0.004 mg/kg in Station 2 and Station 5 respectively during the wet season in the Far eastern zone. The concentrations of organochlorine residues were intermediate in the Eastern zone in both seasons. There was significant (p < 0.05) increase in dry season concentrations when compared to wet season. The risk assessment indicated Hazard Quotient (HQ) > 1 for non-cancer risk and cancer risk > 10-6. Thus a need for stringent monitoring programs for pesticides.

조선후기 영도의 공간적 특성과 경관의 조성

양흥숙 釜山大學校 韓國民族文化硏究所 2015 한국민족문화 Vol.56 No.-

Yeongdo is an inhabited island in the Busan Metropolitan City. Located 200m off the shore, it is made up of a borough. Since the modern times, it became a densely populated area with the progress of industrialization. However, little has been studied about the island before the modern era, and especially during the Joseon Dynasty. This is because the island had been used as a state-operated farm and a prohibited forest, and thereby was regarded unrelated to the general public. This study investigates how Yeongdo, which appeared to have existed unrelated to Busan people, actually existed building its significance in relation to the lives of people. Located at the farthest boundary of Busan port, Yeongdo has been a strategic point of Busan, an important space that protected the Busan port from the field of ocean. This recognition is indicated in old maps and many other ancient documents, suggesting that, rather being unrelated to the people, the island came to hold a place in their memory. Yeongdo, which had existed as a state-operated farm and a prohibited forest, was actually neither a blocked nor prohibited place, but was a place that required people to operate and manage the farm and forest. With the habitation of people, shrines for ancestrial rites appeared in Yeongdo. Thus, the island became a symbolic space. In addition, since Yeongdo was close to the land, it was the closest place to Waegwan, the Japanese residence located on the shore facing the island. Most of the Japanese people who came to Joseon were from Tsushima, and thus felt familiar with the Yeongdo, which had topographical features of an island like Tsushima. In their drawings of Waegwan, the included Yeongdo, as a space with their shrine. Yeongdo, despite its topographic features as an island, was not disconnected from the land but rather existed in constant relationship with the people. Furthermore, it had been building its significance as a place, where people had experiences, a space to remember. 영도는 부산광역시 내에서 육지와 200여 미터 떨어진 가까운 유인도이고 하나의 자치구를 이루고 있다. 근대 이후 공업화가 진행되면서 인구 밀집지역이 되었고 관련 연구성과도 나왔지만, 근대 이전 특히 조선시대의 영도에 대해서는 별로 연구가 이루어지지 못하였다. 국영 목장, 봉산으로 사용되는 곳이었기 때문에 사람들과의 관계가 없는 곳으로 여겨졌기 때문이다. 그러나 사람들과는 무관하게 존재한 것처럼 보였던 ‘섬’ 영도는 실제로는 (육지) 사람의 생활 공간으로 존재하였다. 부산항의 가장 바깥 경계에 위치하면서 부산의 길목이 되기도 하고, 부산항을 해양으로부터 지켜주는 공간이 되기도 하였다. 이런 인식은 古地圖에 나타나기도 하고 여러 고문헌 속에 기록되면서, 사람들과 무관한 것이 아니라 사람들의 기억에 자리할 수 있었다. 국영 목장, 봉산으로 존재한 영도는 차단된, 금지된 공간이 아니라, 이를 운영하기 위한 사람들이 있어야 하는 공간이었고, 사람들이 있으면서 사당(제사 공간)이 생기는 등 상징적인 공간이 될 수 있었다. 또한 육지와 가까웠기 때문에 영도와 마주보는 육지 공간, 즉 일본인 마을인 왜관과 가장 가까웠다. 특히 조선에 온 일본인들은 모두 대마도인들로 대마도와 섬이라는 같은 지형을 가진 영도에 대해 친숙하게 여기고 있었다. 왜관을 그리는 그림에도 영도가 등장하고 그들의 사당도 있는 공간이었다. 영도는 섬이라고 하여 육지와 동떨어진 곳이 아니라, 끊임없이 사람들과의 관계 속에서 존재하였다. 나아가 사람들에게는 경험이 이루어지고 기억이 되는 공간으로 의미를 쌓아가고 있었다.

조선 전·후기 섬에 대한 인식 및 정책 변화 양상 - 전라도 지역을 중심으로 -

임학성 국립해양문화재연구소 2022 해양문화재 Vol.16 No.-

The Joseon Dynasty, having adopted Neo-Confucianism as the basis of its ruling order, applied the principles of Sino-centrism (華夷論) to its spatial awareness and operation. According to this ideology, the dynasty divided its domains into civilized (華) and non-civilized (夷) areas, and considered its islands to belong to the latter group, that is, “barbaric lands” located beyond the reach of the king’s edification. That is how the rulers of the dynasty adopted the “vacant island” (空島) policy, prohibiting its people from inhabiting the islands, except for those close to the mainland or large enough to have a county or prefectural administration. Many of the uninhabited islands were used as state-owned horse farms. It was during the mid-seventeenth century, shortly after Joseon had suffered two devastating invasions, one by the Japanese (Imjin waeran, 1592-98) and the other by the Manchus (Byeongja horan, 1636-37), that significant changes occurred in the Joseon dynasty’s interest in and understanding of the strategic importance of the islands, resulting in the adoption of an entirely new policy. The key to the new policy was the shift from “vacation” to “inhabitation” of the islands and the establishment of naval bases on certain strategic islands. Now the islands began to be perceived as useful parts of the territory. This paper examines changes in the awareness and policies of the Joseon dynasty regarding the importance of its islands through a case study of Jeollado Province. The results are as follows. First, the number of islands identified by the Joseon dynasty increased dramatically, from about 30 in the first half of the fifteenth century to 250 about a century later, and continued to grow to between 430 and 460 by the mid-nineteenth century. Second, there were 34 state-run horse farms on the islands of Jeollado Province in the fifteenth century, but this figure was drastically reduced by more than half, to 15, in the late seventeenth century. Research has also revealed that at least thirtyfour horse farms run by the Joseon dynasty were closed in the mid-Joseon period. This decrease was inversely proportional to the number of islands identified by the government of Joseon after the mid-Joseon period. Third, the abolition of the “island vacation” policy as well as the closure of the state-run horse farms led to a dramatic increase in the number of people inhabiting the islands of Jeollado Province, resulting in the growth of the population by 23% over a thirty-year period in late Joseon. The population of the islands in some counties and prefectures rose by as much as thirty per cent, which contributed to promoting the status of the islands in the administrative units concerned to one equivalent to those of the larger units on the mainland. Fourth, the dramatic increase in the population of the islands of Jeollado Province led to the establishment of new naval bases around the islands. Until the fifteenth or sixteenth century there were only seven naval bases, but the figure doubled to fifteen in the seventeenth and eighteenth centuries. In conclusion, a series of remarkable changes occurred in the islands of Jeollado Province during the late Joseon period. Such changes were largely attributable to the Joseon government’s new understanding of, and increasing interest in, the importance of the islands and to the change of policies occasioned by this new perception of the islands. For the government of the late Joseon period, the islands were no longer a space of separation and isolation but one of communication.

Design and analysis of offshore wind structure

Young-Suk You,Min-Young Sun,Young-Ho Lee Techno-Press 2023 Advances in computational design Vol.8 No.3

The objective of this study was to evaluate the foundation structure of a 3.6-MW wind turbine generator (WTG) installed offshore in Western Korea. The ultimate limit state (ULS) and fatigue limit state (FLS) of the multi-pile steel foundation (MSF) installed at the Saemangeum offshore wind farm were structurally investigated using the finite element (FE) software, ANSYS Workbench 19.0. According to the ULS analysis, no plastic deformation was found in any of the components constituting the substructure. At the same time, the maximal stress value reached the calculation limit of 335 MPa. According to the FLS results, the stress concentration factor (SCF) ranged from 1.00 to 1.88 in all components. The results of this study can be applied to determine the optimal design for MSFs.

국내 해상풍력발전단지 낙뢰피해 영향 분석에 관한 연구

서진규(Jin-Gyu Seo),김규호(Kyu-Ho Kim) 대한전기학회 2016 전기학회논문지 Vol.65 No.2

The latest offshore wind turbines are easily exposed to lightning strikes because they are designed with longer blades and taller height to satisfy the growing capacity demands. The generation facilities and elements of the offshore wind farm are more vulnerable to lightning damage because of more severe, unpredictable weather conditions. Therefore, this paper presents the analysis of measure for lightning overvoltage mitigation in offshore wind farm planned in South Korea southwest seashore. The sensitivity analysis includes the steady state and transient state characteristics of offshore wind farm and proposes the countermeasure for mitigation of transient overvoltage by considering earth resistivity of the offshore environment.