• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
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• pp.502-505
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• 2004

The purpose of this experiment is to modify diagnosis criterion of isothermal relaxation current(IRC) measurement equipment which is using for distribution cable diagnosis. We're using this system for several years in the field instead of DC leakage current measurement and lots of cables were replaced. But we have to investigate on the reliability of this equipment for our cables because we didn't carried out condition assessment of extracted cables after field diagnosis by this equipment. It is important thing for cable maintenance. If the replacement criterion is improper we can not prevent failures or will waste budget on account of replacement of the sound cables. In this papar we selected field installed cables and injected silicone fluid to the cables for insulation rehabilitation. In order to prove reliability of the diagnosis equipment we compared diagnosis results and AC breakdown strength according to operating time after silicone treatment. This is the results of the field test for 1 year.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권5호
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• pp.258-263
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• 2004

The purpose of this experiment is to modify diagnosis criterion of isothermal relaxation current(IRC) measurement equipment which is using for distribution cable diagnosis. We're using this system for several years in the field instead of DC leakage current measurement and lots of cables were replaced. But we have to investigate on the reliability of this equipment for our cables because we didn't carried out condition assessment of extracted cables after field diagnosis by this equipment. It is important thing for cable maintenance. If the replacement criterion is improper we can not prevent failures or will waste budget on account of replacement of the sound cables. In this paper we selected field installed cables and injected silicone fluid to the cables for insulation rehabilitation. In order to prove reliability of the diagnosis equipment we compared diagnosis results and AC breakdown strength according to operating time after silicone treatment. This is the results of the field test for 1 year.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 방전 플라즈마 유기절연재료 초전도 자성체연구회
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• pp.133-137
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• 2004

In this paper, we investigated impurities content, absorption properties, and thermal properties showing by changing the content of carbon black which is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens and absorption properties were measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer) and Karl Fisher. And high temperature, heat degradation initiation temperature, and heat weight loss were measured by TGA (Thermogravimetric Analysis). The dimension of measurement temperature was 0$[^{\circ}]$ to 800$[^{\circ}]$, and rising temperature was 10$[^{\circ}/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result also absorption amount was increased according to these properties. Specially, impurities content values of the A1 and A2 of existing resins were measured more than 4000[ppm]. Heat degradation initiation temperature from the TGA results was decreased according to increasing the content of carbon black. All over, heat stabilities were EEA>EBA>pEVA. That is, heat stabilities of EVA containing the weak VA(vinyl acetate) against heat was measured the lowest.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 방전 플라즈마 유기절연재료 초전도 자성체연구회
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• pp.138-141
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• 2004

In this paper, we Investigated effects on impurities and water of semiconductive shield through a thermal, mechanical, and absorption experiment to estimate performance of insulating materials in power cable. Specimens had been prepared 22[kV], 154[kV] XLPE power cables and then were made of sheet form with XLPE and semiconductive shield with dimension of 0.4[mm] ~1.2[mm] of thickness from power cable. Heat capacity $({\Delta}H)$ and glass trasition temperature (Tg) of XLPE sheet were measured by DSC (Differential Scanning Calorimetry). We could know that thermal stabilities of 154[kV] are more excellent than 22[kV] from this experimental result. The strain of mechanical properties in 22[kV] and 154[kV] XLPE was 486[%], 507[%] and stress was 1.74$[kgf/mm^2]$, 1.80$[kgf/mm^2]$. The absorption contents of existing semiconductive shield were measured 710[ppm] to 1,090[ppm], and semiconductive shield of 22[kV] cable was measured 14,750[ppm] to 24,780[ppm]. We thermal and mechanical properties of 154[kV] could know more excellent than 22[kV] from this experimental result.

• 전기학회논문지
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• 제62권2호
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• pp.239-245
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• 2013

In this paper, we propose a time-frequency domain reflectometry (TFDR) based measurement method for localizing concentric neutrals corrosion on live underground power cable. It consists of two inductive couplers which can transmit the reference signal into live underground power cable and measure the reflected signals from the impedance discontinuities of concentric neutrals corrosion. In order to compensate the dispersion of the measured reflected signal via inductive coupler, an equalizer based on Wiener filtering is designed. To improve the localizing performance of concentric neutrals corrosion in the vicinity of the measurement point, the reference signal is removed from the measured reflected signals. The localization performance of the proposed method is verified by the concentric neutrals corrosion localization experiment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.210-211
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• 2007

The objective of this paper is to effectively detect partial discharges in underground power cables. In this field, we have been usually applied several sensors for such partial discharges. This study used a type of beyond compare antenna based on the influence of background noises. Also, we designed a new structure that is able to easily apply in the adhesion of planar loop types for underground power cables in measurement sensitiveness elevation. A high frequency simulation tool (CST-MWS) was applied to the antenna used in this study, and it was used to evaluate certain characteristics. We fabricated an antenna using the simulation data obtained from a specific test. After checking the sensitivity of this Planar Loop Sensor in the Lab, it was tested in an actual site. This paper analyzed the data as a part of time and frequency domain using an oscilloscope and spectrum analyzer, respectively.

• 대한전기학회논문지:전력기술부문A
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• 제49권12호
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• pp.595-601
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• 2000

This paper describes the improvement method of distance relaying algorithm for the underground transmission cables. Distance relaying algorithms have been mainly developing to protect the overhead transmission lines than the underground cables. If the cable systems are directly protected using distance relaying algorithm developed for overhead line without any improvement, there will be really occurred many misoperation in cable systems, because the cable systems consist of the conductor, the sheath, several grounding method, cable cover protection units(CCPUs), and grounding wire. Accordingly, the complicated phenomena are occurred, if there is a fault in cable systems. Therefore, to develope a correct distance relaying algorithm, such cable characteristics should be taken into account. This paper presents the process to improve distance relaying algorithm which is now used. REal cable system was selected to establish modeling in EMTP and ATP Draw. It was discovered through the detailed simulation during the fault that the large error existed between impedance measured at the relay point and real impedance is due to the resistance of grounding wire in each grounding method. And also compensation factor obtained by the simulation is proposed in this paper. It is proved that the factor proposed can fairly improve the accuracy of impedance at the relay point. It is evaluated that the protective ability will be really much improved, if the algorithm proposed in this paper is applied for cable systems of utility.

• 한국터널지하공간학회 논문집
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• 제19권1호
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• pp.29-39
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• 2017

본 연구에서는 3면이 지중과 접하는 형태의 전력구에서 온도상승을 방지하기 위한 환기시스템 설계에 필요한 벽면에서 열전달계수 등 열설계 자료를 수치해석적인 방법으로 검토하였다. 수치해석 모델은 터널 벽체에서의 열전달을 고려하기 위해서 전력구의 터널의 라이닝을 포함하는 것으로 모델링하였으며, 전력구에 설치되는 전력케이블의 발열량(117~468 kW/km), 전력구내 풍속(0.5~4.0 m/s)에 따른 터널내 공기온도 및 벽체온도, 벽체를 통한 발열량을 CFD시뮬레이션에 의해서 구하였다. 또한 해석결과로부터 벽체열전달계수를 계산하고 환기구간의 터널내 공기온도를 유지하기 위한 한계거리를 검토하였다. 벽체표면에서 대류열전달계수는 입구영역에서는 불안정한 변화를 보이나 약 100 m정도의 이후에는 일정한 값에 수렴한다. 터널벽체열전달계수는 풍속에 따라 $3.1{\sim}9.16W/m^2^{\circ}C$정도이며, 이를 무차원식으로 표현하면 $Nu=1.081Re^{0.4927}({\mu}/{\mu}_w)^{0.14}$이 된다. 열저항 해석기법에 의해서 터널내 온도 예측방법을 제시하였으며, 약 3%이내의 편차로 예측이 가능한 것으로 평가되었다.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.39-46
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• 2015

기중종단 접속함은 지중케이블과 가공송전선을 연결하기 위한 접속함으로써 옥외 변전소 등의 대기 중에 설치된다. 이는 21세기 핵심기술로 여겨지고 있는 대륙 간, 국가 간, 육지-섬을 잇는 HVDC 송전선로의 DC 그리드 송전망 형성을 위해 반드시 개발되어야 하는 전력기기이다. 그러나 AC용 접속함의 개발 사례는 다수 존재하는 반면, DC용 접속함의 개발 사례 및 기술은 일본과 중국 등에 일부 존재할 뿐 국내 기술은 부족한 실정이다. 따라서 본 논문에서는 기존 AC용 슬립 온형 기중 종단접속함을 초기모델로 선정하여 HVDC 전력기기로의 적용 가능성을 평가하였다. 먼저 실제 운전 시 기중종단 접속함 내 도체에서 발생하는 열에 의한 내 외부의 온도편차를 고려한 DC 전계해석을 수행하였으며, AC 전계분포 및 열 해석이 반영되지 않은 DC 전계분포와 비교하였다. 또한 DC 전계는 정상상태 뿐만 아니라 과도 구간도 포함하기 때문에 이를 고려한 전계해석을 수행할 필요가 있기 때문에 정상상태와 더불어 극성반전 후 전계분포 역시 비교, 분석하였다. 마지막으로, 기존 AC용 슬립 온형 기중 종단접속함 초기모델을 DC에 적용하기 위해 다양한 형상 변환을 통한 요소 설계를 수행하였다. 기중종단 접속함 구조 내 전계가 가장 집중될 것으로 사료되는 부분을 선정하여 그 지점들의 최대 전계강도 $E_{n.max}$와 $E_{t.max}$를 측정하였다. 해석 결과, 정상상태시 개선모델의 삼중점 최대 전계강도는 기준모델 대비 2.01% 개선되었으며, 연면 최대 전계강도는 기준모델 대비 36.68% 개선되었다. AC 전계해석 결과인 연면 전계강도 1.11 kV/mm보다는 33.3% 감소하였지만 삼중점 최대 전계강도 8.23 kV/mm보다는 아직 43.6% 크다는 점에서 부분적인 형상 변환이 아닌 DC 환경에 적합한 전혀 다른 근본적인 설계 개념의 변화가 반드시 필요할 것으로 사료된다.