• 한국전자파학회논문지
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• 제23권8호
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• pp.985-994
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• 2012

본 논문에서는 wireless body area network(WBAN) 채널을 분석하기 위해 실제 채널을 측정하고, 그것의 통계적 특성들을 조사하였다. On-/off-body 채널에서, 인체의 움직임을 고려하기 위해 대표적인 움직임들을 같이 측정하여 그 분석 결과들을 비교하였다. 또한, 세 종류의 신호 전송 기법을 제한된 Outage 확률을 가질 때 최소 소비 전력을 분석하여, 이론적인 총 전력 소비를 계산하였다. 그리고 채널 측정 데이터들을 통해 이론과 실제의 차이를 분석하였다. 본 논문의 결과로 협력 통신을 통하여 전송 효율을 높일 수 있음을 알 수 있으며, 센서 노드의 부착 위치와 움직임이 신호 전송 전력에 어떠한 영향을 미치는지 확인할 수 있다.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.961-968
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• 2016

The non-uniform distribution of contamination on insulator surface has appreciable effects on flashover voltage, and corresponding researches are valuable for the better selection of outdoor insulation. In this paper, two typical types of porcelain and glass insulators which are widely used in ac lines were taken as the research subjects, and their corrections of AC flashover voltage under non-uniform pollution were studied. Besides, their flashover characteristics under different ratio (T/B) of top to bottom surface salt deposit density (SDD) were investigated, including the analysis of flashover voltage, surface pollution layer conductivity and critical leakage current. Test results gave the modified formulas for predicting flashover voltage of the two samples, which can be directly applied in the transmission line design. Also, the analysis delivered that, the basic reason why the flashover voltage increases with the decrease of T/B, is due to the decrease of equivalent surface conductivity of the whole surface and the decrease of critical leakage current. This research will be of certain value in providing references for outdoor insulation selection, as well as in proposing more information for revealing pollution flashover mechanism.

• 전기학회논문지
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• 제60권5호
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• pp.999-1004
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• 2011

Nowadays, it is becoming difficult to secure a transmission line route when a new transmission line is constructed due to social environment and resident complaints. As existing urban areas are expanded and new cities are constructed, the necessity of high-capacity underground power transmission has been increasing because of load concentration in downtown areas. In North America, Europe and Japan, the research has been carried out for 2nd generation gas insulated transmission lines(GIL) which is more environmentally friendly and economical compared to previous GILs. The new GILs have been applied to real power systems from early 2000s. In South Korea, GIL is being considered as a possible solution for replacing 345kV high-capacity overhead transmission lines with underground transmission ones, so KEPCO is planning to develop and apply a new 362kV rated GIL underground transmission lines instead of overhead transmission lines. In this paper, the overvoltage generated at the combined transmission line adapting GIL was reviewed using EMTP.

• 조명전기설비학회논문지
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• 제24권10호
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• pp.123-129
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• 2010

During the past 2 decades, many electric power companies have been searching various solutions in order to supply power with economical and more efficiency in the present transmission utilities. Most interesting method to increase the line capacity of overhead transmission lines without constructing any new line might be to adapt Dynamic Line Rating(DLR). Specified rating is normally determined by any current level, not by conductor temperature. Although specified rating is essential to design transmission line, dip may be the most important factor in limiting transmission capacity. Transmission lines built by the oldest dip criterion among the 3 different design criteria for conductor dip are nearly over one-half of all Kepco's transmission lines. This paper describes an up-rating method for those transmission lines in order to apply DLR technique. Based on limit dip conductor temperature and current of the transmission lines, limitation performance and effectiveness in applying DLR with weather model are analyzed. As a result of analysis, it can be shown that an improved method could be effectively used for increasing the line rating of old transmission line which was built by the design criterion with low dip margin.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.991-996
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• 2014

Power frequency magnetic field is still a critical problem for new construction of overhead power transmission lines in Korea because most people have been concerned about possibly carcinogenic effects of it. Although reference level of power frequency(60Hz) magnetic field has been set to 200uT in ICNIRP guidelines published in 2010, Korean government has no intention of adjusting 83.3uT specified by law in 2006 to this new reference level in consideration of people's concerns for the time being. Regardless of the current regulated magnetic field value, electric utility company has been trying to reduce magnetic field in the residential area in the vicinity of overhead power transmission lines to take into account of public concerns on the long-term effect of magnetic fields. In an effort to reduce magnetic field, engineering side has made considerable efforts to develop passive loop based, cost-effective mitigation technique of power frequency magnetic field more than ten years. In order to verify developed power frequency magnetic field mitigation technique based on passive loop, a horizontal type of passive loop was designed and installed for commercially operating 154kV overhead power transmission line for the first time in Korea. The measurement results before and after the installation of passive loop showed that magnetic field could be reduced to about 20%. The electrical environmental effects such as AN, RI and TVI were assessed before and after the installation of passive loop and these values were complied with the requirements specified by electric utility. It has been confirmed from the field test results that passive loop could be commercially and cost-effectively utilized to mitigate power frequency magnetic field.

• Transactions on Electrical and Electronic Materials
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• 제17권1호
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• pp.1-6
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• 2016

Ensuring the secure operation of power systems has become an important and critical matter during the present time, along with the development of large, complex and load-increasing systems. Security constraints such as the thermal limits of transmission lines and bus-voltage limits must be satisfied under all of a system’s operational conditions. An alternative solution to improve the security of a power system is the employment of Flexible Alternating-Current Transmission Systems (FACTS). FACTS devices can reduce the flows of heavily loaded lines, maintain the bus voltages at desired levels, and improve the stability of a power network. The Unified Power Flow Controller (UPFC) is a versatile FACTS device that can independently or simultaneously control the active power, the reactive power and the bus voltage; however, to achieve such functionality, it is very important to determine the optimal location of the UPFC device, with the appropriate parameter setting, in the power system. In this paper, a genetic algorithm (GA) method is applied to determine the optimal location of the UPFC device in a network for the enhancement of the power-system loadability and the minimization of the active power loss in the transmission line. To verify our approach, simulations were performed on the IEEE 14 Bus, 30 Bus, and 57 Bus test systems. The proposed work was implemented in the MATLAB platform.

• 전기전자학회논문지
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• 제22권1호
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• pp.216-222
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• 2018

장거리 무선전력전송 기술은 단순한 핸드폰 및 소형가전을 넘어서, 4차 산업혁명의 핵심기술로 자리 잡은 드론, 로봇, 전기자동차, IoT 센서 네트워크 등에 폭넓게 적용될 수 있다. 본 논문에서는 이미 기술적으로 보편화된 기존의 근거리 무선전력전송 기술을 벗어나, 급속한 기술발전으로 통하여 상용화 단계에 이른 장거리 무선전력전송 기술의 발전방향을 살펴보고자 한다. 이를 통하여, 핵심기술을 파악과 기술적인 극복과제를 도출함으로써 국내의 연구수준과 나아갈 바를 점검하고자 한다.

• ETRI Journal
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• 제36권2호
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• pp.313-316
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• 2014

Energy consumption is an important issue in body area networks (BANs). In this letter, we propose an energy efficient transmission power control scheme for IEEE 802.15.6 BANs, which can improve energy efficiency by adaptively adjusting the transmit power in an on-demand way to adapt to varying channel environments. Simulations are performed to evaluate the performance, and it is shown that the proposed power control scheme outperforms traditional ones in terms of energy efficiency without significant reliability degradation.

• 한국전기전자재료학회논문지
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• 제23권10호
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• pp.809-813
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• 2010

Frequency domain measurement of propagation loss for ultra high frequency (UHF) partial discharge in the winding of power transformer using a spectrum analyzer and pulse generator is presented. We compared the performance of the method using a network analyzer with and without a winding. Using a network analyzer simplifies the measurement and offers better dynamic range and frequency range. It also provides precise propagation loss within the winding in frequency domain at UHF range. We applied this method to measure UHF propagation loss of transformer mock-up, modeled 154 kV 20 MVA power in KEPCO substation.

• 조명전기설비학회논문지
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• 제26권12호
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• pp.74-79
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• 2012

Currently, separated buses were increased to limit a fault currents in power transmission system. However, separated buses caused bad influences such as a decrease of reliability and stability. Superconducting fault current limiter (SFCL) was proposed to limit a fault current lately and that has many merits beside any other solutions. Therefore, we proposed the install of Superconducting fault current limiter (SFCL) in power transmission system with separated bus. And our proposal was verified by reliability of power system.