• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.123-127
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• 2020

KEPCO has installed Frequency Regulation ESS (FR ESS) of 376 MW since 2015. Frequency Regulation is ancillary service to support stabilizing system frequency, which is divided into governor free and automatic generation control. KEPCO operates FR ESS as governor free application and leads FR ESS market with capability of diverse demonstration and operation experiences. To expand FR ESS role during transient states of power system, KEPCO has extended operating time of charging and discharging. KEPCO has also changed speed droop lower than before to improve contribution on frequency compensation, and acquired much experiences of differentiating bad cells from others. Based on these technologies and know-hows, KEPCO Research Institutes received request of feasibility study and technical cooperation for overseas FR ESS business. This paper suggests the simple and practical method for making technological feasibility study of FR ESS.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.151-155
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• 2020

In this paper, a new experimental method to determine the thermal resistance of building wall was proposed by improving the heat flow method (HFM) based on the air-surface temperature ratio theory. This technique measures the thermal resistance of the wall excluding the inner and outer surface heat transfer resistance. Unlike conventional HFM, this value can be compared directly with the theoretical reference value. Its performance was verified using three mock-up structures with a theoretical thermal transmittance of 0.5, 3.3, and 0.18 W/㎡·K respectively. After measuring the variations in the temperature and heat transfer rate of the mock-ups for 383 hours, the thermal transmittances were determined to be 0.47, 3.10, and 0.18 W/㎡·K, which corresponded to errors of 5.2, 6.2 and 0.5%, respectively, compared to the theoretical values. It was concluded that this technique can directly compare the thermal resistance of the wall between the existent stage and initial stage after construction.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1585-1592
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• 2008

산업사회의 발전에 따라 사회 기반시설분야도 복잡다양해지고 특히 도시기능이 활발해지면서 지금의 도심지에는 지하철, 상수도, 하수도, 전력구, 통신구, 지하보차도, 지하상가, 지하주차장 등 여러 가지 용도의 지하공간이 요구되고 있으며, 이러한 지하 구조물을 축조하는데 있어 도로상에 차량 증가로 인한 교통 혼잡이나, 지하매설물의 장애로 인하여 기존의 개착식 공법으로 시행하지 못하고 지하터널공사로 시행하는 경우가 빈번하다. 기존 국내 외 터널공법 관련문헌과 현재 사용되는 터널공법의 실제 시공에 관한 정보를 수집하여 장 단점, 시공시 주의사항, 적용조건등의 조사내용을 바탕으로 RPS 공법을 고안하였다. 소규모 지하구조물을 구축하기 위한 RPS 공법은 출발갱내에서 상부에 파이프 루프를 시공한 후 광폭 유압 패널이 장착된 철제 선도관을 추진시켜 선도관을 원압잭에 의하여 압입한 후 P.C. 콘크리트 구조물을 거치하고 원압으로 압입 추진토록 하였다. 또한, 대규모 지하구조물 축조시에는 구조물 예정상단부에 지반조건에 따라 파이프 루프공법 또는 소구경 Semi-Shield 공법을 이용하여 루프를 시공함으로써 상부의 침하를 방지하고, 측벽은 광폭유압 패널을 이용하여 여굴의 최소화 및 곡선부 시공을 용이하게 하였다.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1912-1914
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• 2000

This is the first report of a series of field test result of large high voltage generator & motors. Major specimens were 6.6/13.2kV class hydroric power & pump motor that was installed and operated for public water service by KOWACO(KOrea WAter resources COperation). The capacity of specimen gene rater & motors were in range of several hundred kVA$\sim$50MVA. Until now, we get the 100 field test result by testing technique discribed in IEEE standards and Discharge map technique from Japanse manufactures. The test result was varied very wide range, and there was a tendency according to insulation material and manufacture.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.33-41
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• 2016

To verify that the friction damper used to high buildings as a kind of control technology of wind vibration can reduce dynamic behaviors of PTTs effectively, slip dampers in this paper are proposed to absorb the energy through relatively frictional movement of slip dampers applied to main post of a PTT (Power Transmission Tower) when dynamic displacement of a PTT occurs. The result of dynamic analysis is presented to determine the capacity of the damper system by controlling damping ratio on the resonance condition. It is observed that by installing slip dampers at a PTT the strain amplitudes of the main post caused by wind load are effectively reduced. Therefore it is shown that the proposed damper satisfies the strengthened wind-load design standards, and its efficacy was also validated experimentally by field testing.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.21-27
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• 2015

The goal of this study is the size and distribution of the electromagnetic force generated by the current flowing through the second underground line of 154kV power transmission cables by using electromagnetic finite element analysis. So we interpret how mutually electromagnetic force has an effect on the comparable judgement of Trefoil, Duct and Flat, which shows in a numerical arrangement. 154kV OF 1200SQ Cable 1.281km not only is applicable to modeling for underground transmission cable but also examine the effect of line to line, phase to phase and size and direction of the electromagnetic force preparing for the occurrence of normal state and single-phase earth fault, which are arranged in trefoil, duct and flat formation between sections. As showing how the trajectory, and size distribution of the electromagnetic force translate as the arrangement of the cables when a steady-state current and a fault current flows on the underground cables, I hope that when Underground transmission is designed, this data will be useful information.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.151-156
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• 2015

In order to improve the properties of high-temperature superconducting wire for superconducting cable system, we optimized the electro-polishing (EP), ion-beam assisted deposition (IBAD), superconducting (SC) layer, and baking (heat) treatment. The buffer layer was deposited on electro-polished substrate with RMS roughness ($R_{RMS}$) less than 5 nm. The IBAD process was carried out at $V_{beam}$: 1100 V and $V_{accel}$: 850 V that resulted in highly crystalline film of $LaMnO_3$. Chemical composition of SC layer is key to higher critical current, and we found that composition can be determined by surface color of SC layer. We adopt a proprietary contorl system based on RGB analysis of the surface and achieved critical current of 150 A/4 mm-width. The proposed baking treatment resulted in decreasing of about 10% of fraction defects.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.9-13
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• 2015

Energy storage systems (ESS) can be used to provide frequency regulation services in a power system to replace traditional frequency regulation power plants. Battery ESS, in particular, can provide "fast-responding frequency regulation," wherein the facility can respond immediately and accurately to the frequency regulation signal sent by the system operator. This paper presents the development and the trial run results of a frequency regulation control system that uses large-scale ESS for use in a large power system. The control system was developed initially for the 4 MW ESS demonstration facility in Jocheon Jeju Island, and was further developed for use in the 28 MW ESS facility at the Seo-Anseong substation and the 24 MW ESS facility at the Shin-Yongin substation to provide frequency regulation services within mainland Korea. The ESS facility in Seo-Anseong substation responds to a sudden drop in frequency via governor-free control, while the ESS facility in Shin-Yongin responds via automatic generator control (AGC).

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.121-125
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• 2015

Distribution of rare earth metals (REMs) and rare valuable metals (RVMs) contents in coal ashes (fly ash, bottom ash, and pond ash) and leachate from 11 coal-fired power plants in Korea were investigated. Coal ashes and leachates were found to contain important REMs and RVMs such as Yttrium (Y) and Neodymium (Nd), which was in the range of 23~75 mg/kg. However, it still requires developing effective recovery and separation methods in order to utilize REMs and RVMs in ash and leachate. Recovery of valuable elements (Y and Nd) from various and extensive ash sources (8.21 million tons/year in 2013) can provide the existing power plants with additional profit; therefore, it can significantly improve economics of the power plants.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.127-131
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• 2016

Polymer electrolyte membrane for unitized regenerative fuel cells requires high proton conductivity, high dimensional stability, low permeability, and low cost. However, DuPont's Nafion which is a commercial polymer electrolyte membrane has high permeability, high cost, and decreasing proton conductivity and dimensional stability over $80^{\circ}C$. To address these problems, sulfonated poly ether ether ketone (sPEEK) which is a low cost hydrocarbon polymer is selected as matrix polymer for the preparation of polymer electrolyte membrane. In addition, composite membrane with improved proton conductivity and dimensional stability is prepared by introducing sulfonated graphene oxide (sGO). The fundamental properties of polymer electrolyte membranes are analyzed by investigating membrane's water content, dimensional stability, proton conductivity, and morphology. The cell test is conducted to consider the possibility of application of sPEEK/sGO composite membrane for an unitized regenerative fuel cell.