• 제목/요약/키워드: Mal-Operation

검색결과 65건 처리시간 0.027초

VHDL을 이용한 동기탈조 검출 알고리즘 구현에 관한 연구 (A Study on Implementation of Out-of-Step Detection Algorithm using VHDL)

  • 김철환;권오상
    • 대한전기학회논문지:전력기술부문A
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    • 제55권5호
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    • pp.179-184
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    • 2006
  • In a power system, an out-of-step condition causes a variety of risk such as serious damage to system elements, tripping of loads and generators, mal-operation of relays, etc. Therefore, it is very important to detect the out-of- step condition and take a proper measure. This paper presents a study on implementation of out-of-step detection algorithm using VHDL(Very high speed Hardware Description Language). The structure of out-of-step detection algorithm is analyzed for development of out-of-step detection relay on the FPGA(Field Programmable Gate Array). The out-of-step algorithm is separated to 4 parts: DFT IP, complex power calculation IP, out-of-step detection IP, control unit. Each parts are developed and simulated by using VHDL.

부하에 따른 voltage sag의 특성 분석 (Analysis of voltage sag characteristics according to loads)

  • 최현영;류형선;오세호;박정균;김양모
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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    • pp.236-238
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    • 2001
  • Voltage sags are known as a serious problem causing mal-operation of equipment, process controllers and adjustable-speed drives. In this paper various analysis techniques for voltage sags will be presented, voltage sag characterization, equipment behaviour during voltage sag, stochastic assessment of voltage sags. And possible solution to voltage sag sensitivity problems are also described.

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Modified Differential Protection for Transformers in Wind Farms

  • George, Sujo P.;Ashok, S
    • Journal of Electrical Engineering and Technology
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    • 제13권1호
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    • pp.78-88
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    • 2018
  • The liberalization of electricity market and environmental concerns are the major driving forces for the development of Distributed Generation (DG). The mode of grid-connected wind power generation is becoming popular and has matured as a reliable DG technology. The voltage generated by the wind generator is stepped up to the higher voltage by the transformers before connecting to the grid. Operating algorithm of the differential relays for transformer protection used in the wind farms need to be modified to take care of the dynamic nature of fault current caused by the intermittent nature of the wind power. An algorithm for the differential relay is proposed in which dual slope characteristics are adjusted with varying fault level situation according to the wind generator in service as well as with the wind speed. A case study conducted for a typical wind farm shows that the proposed method avoids mal-operation of the differential relay in varying wind power conditions.

Voltage sag의 특성과 dq좌표변환을 이용한 검출법에 대한 연구 (The Characteristics of Voltage Sag and a Study about Detection Algorithm Using the DQ Transformation)

  • 김용상;김도훈;임상욱;이교성;김양모
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2003년도 하계학술대회 논문집 B
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    • pp.1114-1116
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    • 2003
  • Voltage sags are known as a serious problem causing mal-operation of equipment like computers, process controllers and adjustable-speed drives. In this paper, characterization of voltage sag and an overview of methods used in the mitigation of voltage sags are presented. Moreover a fast detection method for voltage disturbances is explored. The algorithm is based on the theory that allows a set of three-phase voltages be converted the d-q value. The utility input voltages are sensed and then converted to some quantities in the d-q transformation. And the difference between reference value and input value are showed that some disturbances happened in the system.

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유기전압비를 이용한 디지털형 변압기 보호계전기 개발 및 성능시험에 관한 연구 (A Study on The Development and Function Test of Digital Transformer Protection Relay Using The Induced Voltage)

  • 정성교;이재경;김한도;최대길;강용철;강상희
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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    • pp.216-218
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    • 2001
  • The transformer role is very important in power system operation and control; also its price is very expensive. Therefore many kinds of the efforts for transformer protection have been executed. So for as, current differential relay(87) has been mainly used for transformer protection. But current differential relaying method has several troubles as followings. Differential current can be occurred by transformers inrush current between winding1 and winding2 of transformer when transformer is initially energized. Also harmonic restrained element used in current differential relaying method is one of the causes of relays mal-operation because recently harmonics in power system gradually increase by power switching devices(SVC, FACTS, DSC, etc). Therefore many kinds of effort have been executed to solve the trouble of current differential relay and one of them is method using ratio of increment of flux linkages(RIFL) of the primary and secondary windings. This paper introduces a novel protective relay for power transformers using RIFL of the primary and secondary windings. Novel protective relay successfully discriminates between transformer internal faults and normal operation conditions including inrush and this paper includes real time test results using RTDS(Real Time Digital Simulator) for novel protective relay. A novel protective relay was designed using the TMS320C32 digital signal processor and consisted of DSP module. A/D converter module, DI/DO module, MMI interface module and LCD display module and developed by Xelpower co., Ltd.

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환자 선호도를 고려한 음악중재가 척추 마취 환자의 수술 중 불안, 활력 징후 및 혈당에 미치는 영향 (Effects of Preferred Music Intervention on Anxiety, Vital Signs and Blood Sugar of Surgical Patients Undergoing Operation Using Spinal Anesthesia)

  • 정향미;박말영;이수진;김남희
    • 동서간호학연구지
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    • 제20권1호
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    • pp.9-20
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    • 2014
  • Purpose: The purpose of this research was to examine the effects of preferred music intervention on anxiety, vital signs and blood sugar of surgical patients undergoing spinal anesthesia. Methods: A quasi-experimental research with non-equivalent control group non-synchronized design was carried out. Subjects consisted of 40 patients (experimental group 20, control group 20) who were scheduled to undergo surgery with spinal anesthesia. During the operation, music individual patients preferred was provided to the experimental group. The data were collected from July 4 to November 10, 2011 and analyzed with descriptive statistics, t-test, chi-square test, ANCOVA and repeated measured ANCOVA using SAS (ver 9.2). Results: 1) Patient anxiety during the operation of the experimental group was significantly lower than the control group (F=93.77, p<.001). 2) There was no significant difference in diastolic blood pressure (F=.00, p=.979), Systolic blood pressure (F=.19, p=.668), heart rate (F=.00, p=.955), and blood sugar (F=.73, p=.399) between the experimental group and the control group. Conclusion: Letting patients hear their preferred music during surgery is an effective nursing intervention to relieve anxiety of patients undergoing surgery with spinal anesthesia.

프랜차이즈 모기업 핵심역량 자원이 가맹점 관계결속과 재계약의도에 미치는 영향 (Effects of Core Competence and Resource Sharing on the Relational Bond among Franchisees and on Re-contract Intention in the Franchising Parent Companies)

  • 허영욱;주말찬
    • 유통과학연구
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    • 제12권4호
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    • pp.11-22
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    • 2014
  • Purpose - The domestic franchise industry has made significant contributions to industry such as investment, employment, and community economy development, facilitating growth potential. The franchise industry provides management knowhow transfer between parent companies and franchisees as per contracts addressing use of business signs, franchisees' independent position, franchisor support, and royalties to be paid to the franchisors. However, many franchisors lack management knowhow and provide insufficient support because of poor control of franchisees and not having a systematic approach to support. This results in dissatisfied franchisees and failure to establish long-term relationships. Few studies have examined relational commitment and/or re-contract intention by support resources between franchisors and franchisees, despite a considerable output of theories and studies of the growth of the franchise industry. The purpose of this study, therefore, was to examine the effects of the ability to provide resources on relational commitments and re-contract intention, and to suggest causal relationships and implications. Research design, data, and methodology - The subject was domestic franchisors registered with the Association of Franchise with more than 50 franchisees. Franchisees under contract for 2 years and considering re-contract of their franchise 2 years later were used. The subjects totaled 300 franchisees in Seoul. A questionnaire survey was used to investigate the subject of franchisees' concessions during the 10 days from November 21, 2013 to November 30, 2013. After excluding 16 surveys with poor answers, 284 responses were finally used. Four areas and 44 questions were used. A nominal scale was used for four common characteristics questions including gender, ages, educational background, and franchise managing time. Questions regarding ability, relational commitment, and re-contract intention made use of a Likert 5-point scale. Data coding and data cleaning were used. SPSS 18.0 was used as follows. First, frequency analysis was done to investigate demographic characteristics. Second, exploratory factor analysis was done to verify validity of testing tools, and Cronbach's α coefficient was used to verify reliability. Third, correlation analysis and multiple regression analysis were done. An exploratory factor analysis was done to verify validity of concepts. A correlation analysis was done to test relationships between the variables, and multiple regression analysis was done to verify franchisor's ability, franchisees' relational commitment, and re-contract intention. Results - The following were the outcomes. First, store operation management, finance operation management, and human resource management affected the calculated bond. Second, store operation management and finance operation management affected the emotional bond. Third, store operation management, finance operation management, human resource management, and marketing management affected the prescriptive bond. Fourth, calculated bond and prescriptive bond had an effect on re-contract intention. Conclusions - As stated above, in franchise management, parent companies' offer and instruction of core competence to their franchisees as an information resource could improve the relational bond by helping them grow together through the resource sharing. Consequently, core competence factors were promoting factors that could improve franchisees' re-contract intention for a long time.

다른 수분함량으로 압출성형한 다수확 멥쌀가루의 이화학적 특성 (Physicochemical Properties of High Yielding Non-waxy Rice Flours Extruded with Different Moisture Contents)

  • 정소희;강위수;신말식
    • 한국식품조리과학회지
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    • 제27권6호
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    • pp.745-754
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    • 2011
  • To improve the textural properties of gluten free rice flour based products, the physicochemical and pasting properties of extruded non-waxy rice flours using extruder were investigated. The high yielding Tongil type rice variety, Hanarum was used. Hanarum rice flour was prepared by dry milling from soaked and dried rice grain. The operation conditions of twin screw extruder were 250 rpm of screw speed, $160^{\circ}C$ of barrel temperature, and 24, 27, and 30% of moisture content. Hanarum extruded rice flour (HERF) were lower in crude lipid and ash contents, but higher in crude protein than Hanarum rice flour (HRF). The color values of HERF showed significantly different (p<0.05) with different moisture contents. Water binding capacities, apparent amylose contents, and damaged starch of HERF were higher than those of HRF. Moisture contents affected water binding capacities of HERF. Solubility increased with increasing heating temperature and solubilities of HERF differed significantly (p<0.05). X-ray crystallinity was changed after extrusion cooking and that of HERF showed sharp peaks at $2{\theta}=18-20^{\circ}$. The pasting viscosities of HERF kept lower values (~ 10 RVU) constantly.

WLAN/WiMAX용 삼중대역 마이크로스트립 안테나 설계 (Design of Triple-Band Microstrip Antenna for WLAN/WiMAX)

  • 오말근;김갑기
    • 한국인터넷방송통신학회논문지
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    • 제14권4호
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    • pp.213-217
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    • 2014
  • 본 논문에서는 WLAN/WiMAX 시스템에 적용 가능한 모노폴 마이크로스트립 안테나를 설계하였다. 제안된 모노폴 안테나의 기판은 FR-4이고 크기는 $30mm{\times}40mm$이다. 제안된 안테나는 평면형 모노폴 설계를 기본구조로 구성함으로서 WLAN/WiMAX 대역을 포함하는 삼중대역 특성을 갖도록 설계하였다. 최적화된 파라메타를 얻기 위해 상용 툴(CST's Microwave Studio Program)을 사용하여 시뮬레이션 하였으며 안테나 성능에 민감하게 작용하는 파라메타를 찾아내서 최적화된 수치를 얻었다. 얻어진 최적화된 수치를 사용하여 제안된 안테나를 설계하였다. 따라서 제안된 안테나는 WLAN/WiMAX 대역을 동시에 만족하였다. 그리고 WLAN/WiMAX 대역에서 이득과 방사패턴의 특성을 얻었다.

개선된 변류기 2차 전류 보상 알고리즘 (An Advanced Algorithm for Compensating the Secondary Current of CTs)

  • 강용철;임의재
    • 대한전기학회논문지:전력기술부문A
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    • 제52권7호
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    • pp.387-392
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    • 2003
  • During a fault the remanent flux in a current transformer (CT) may cause severe saturation of its core. The resulting distortion in the secondary current could cause the mal-operation of a protection relay. This paper proposes an algorithm for compensating for the errors in the secondary current caused by CT saturation and the remanent flux. The algorithm compensates the distorted current irrespective of the level of the remanent flux. The second-difference function of the current is used to detect when the CT first starts to saturate. The negative value of the second-difference function at the start of saturation, which corresponds to the magnetizing current, is inserted into the magnetization curve to obtain the core flux at the instant. This value is then used as an initial flux to calculate the actual flux of the CT during the course of the fault with the secondary current. The magnetizing current is then estimated using the magnetization curve and the calculated flux value. The compensated secondary current can be estimated by adding the magnetizing current to the secondary current. Test results indicate that the algorithm can accurately compensate a severely distorted secondary current signal.