• KEPCO Journal on Electric Power and Energy
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• v.3 no.2
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• pp.141-146
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• 2017

In this work, a simulation study on net 500 MW class of Poly-Generation was conducted for the retrofit of an aged natural gas combined cycle. An entrained gasifier which has a capacity of maximum $260,000Nm^3/h$, 50 MW class of a Polymer Electrolyte Membrane Fuel Cell, and H-class Gas Turbine were selected as key processes. After unit design for those employed processes was set up and combined, the simulation was carried out with Gate-Cycle software (Ver. 6.0) for two cases. The selected cases are a retrofit type (Poly-Gen 1) and a new type (Poly-Gen 2). It was found that the efficiency of the retrofit case is 2.7% lower than that of the new case.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.561-562
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• 2015

2013년 이후, 한국전력공사에서는 신규건설 변전소로 디지털변전소(Digital Substation)를 건설하고 있다. 디지털변전소 내에는 서버(IED, 지능형전자장치), 클라이언트(상위운영시스템)가 필수요소들이며, 이 둘은 서로 서버/클라이언트 통신 서비스를 수행하고 있고 IEC61850 기반으로 하고 있다. 바뀐 정책과 프로토콜 때문에 사용되는 기기 역시 기존 디지털 보호 계전기에서 IED로 성능이 변화하였고, 기존에 수행하던 보호성능검증 방법인 동특성시험 역시 IEC61850 기반 통신서비스 성능도 함께 보아야 한다는 관점에서 본 연구가 시작되었다. 본 논문에서는 RTDS를 이용한 IEC 61850 기반 IED 동특성 시험 성능검증 방법에 대하여 살펴보고, 그 결과를 알아보고자 한다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.374-378
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• 2008

The analysis about cases which does not correspond in electric equipment technical standard and judgement standard while doing pre inspection, it improves the technical specifications and the draft of construction plan. The analysis of the reform cases prevents the electric disaster and propagates the electrical safety. Hereafter the reform cases will improve the electric technical ability and help the electrical safety of the yard.

• Fire Science and Engineering
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• v.16 no.4
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• pp.49-58
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• 2002

A large number of accidents at an underground place have been happening, including the gas explosion under construction of subway; the fires of underground utility and underground shopping malls, and other explosion, at home and abroad recently. These accidents make the function of a city ineffective due to the paralyses of electricity and communications net as well as the loss of property and cause people to feel unsecured with accompaniment of a heavy of toll of lives. This research will show evaluation methods of a numerical value of expected average loss space of combustion with the use of probability in order to present potential risk of combustion growth that underground space might cause, and how designer decides a system that enables us to compare and evaluate relatively the effectiveness of measures for preventing burning by calculating the expansion route and the damage size of burning in case of fire.

• Proceedings of the KSEE Conference
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• 2008.10a
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• pp.17-28
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• 2008

국책사업이나 SOC의 확충을 위한 도로 및 철도의 건설에서 적용되는 터널의 단면크기를 보면, $50m^2$에서부터 $100m^2$이상의 중 대단면 터널이 주를 이루고 있으나, 전력구, 통신구, 소규모로 운영되는 광산의 채광용 터널, 용수를 위한 도수로터널 등 특수한 용도로 설계, 시공되고 있는 터널에서는 $20m^2$이하의 단면크기를 갖는 경우가 있다. 이러한 소단면 터널의 경우에는 협소한 작업공간으로 인하여 적용공법 뿐만 아니라 장비의 사용 또한 제약을 받게 되어 작업효율이 저하되고 공사기간이 늘어나게 되는 등 여러 가지 문제점을 안고 있다. 특히, 에멀젼 폭약을 사용하는 발파에서 먼저 기폭된 발파공의 충격압력에 의해 인접공의 폭약이 예비압축(Precompression)되어 사압현상을 일으키고 잔류약을 발생시키는 사례가 종종 발생하고 있다. 사압현상은 당해 발파의 실패와 함께 2차적인 사고의 위험요인이 될 수 있으므로 이를 방지하기 위한 대책을 수립하여야 한다. 이를 위해 기존 문헌을 통하여 사압현상의 원인과 발생 가능성을 검토하였고, 국내에서 주로 사용되는 에멀전폭약의 수중 내충격성시험과 충격압력 전달시험을 실시하여 사압현상의 발생정도를 측정하였으며, 사압현상이 발생한 소단면 터널현장을 대상으로 대책을 수립하여 적용하였다. 심발방법을 변경하여 전단의 충격압력을 견딜 수 있는 공간격을 확보하고 뇌관의 초시간격을 적절하게 배치한 발파패턴을 적용한결과, 사압현상을 억제하고 잔류약의 발생을 감소시켜 계획 굴진장을 확보하고 파쇄석의 크기를 감소시키는 등 양호한 결과를 얻을 수 있었다.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.307-310
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• 2016

The operational cost for maintaining the superconductivity of high-temperature superconducting (HTS) cables needs to be reduced for feasible operation. It depends on factors such as AC loss and heat transfer from the outside. Effective operation requires design optimization and suitable operational conditions. Generally, it is known that critical currents increase and AC losses decrease as the operational temperature of liquid nitrogen ($LN_2$) is lowered. However, the cryo-cooler consumes more power to lower the temperature. To determine the effective operational temperature of the HTS cable while considering the critical current and AC loss, critical currents of the HTS cable conductor were measured under various temperature conditions using sub-cooled $LN_2$ by Stirling cryo-cooler. Next, AC losses were measured under the same conditions and their variations were analyzed. We used the results to select suitable operating conditions while considering the cryo-cooler's power consumption. We then recommended the effective operating temperature for the HTS cable system installed in an actual power grid in KEPCO's 154/22.9 kV transformer substation.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.245-251
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• 2016

Despite the exponential throughput improvement in mobile communications systems, their ability to satisfy requirements of state-of-the-art and future applications of advanced metering infrastructure (AMI) is still under investigation. Challenges are mainly due to the inadequacy of third generation partnership project (3GPP) networks to support large amounts of devices simultaneously, while the number of AMI end-devices and the frequency of their data transmission increase with new AMI-based applications. In this introductory survey, innovative and future AMI applications and their communication requirements are first reviewed. Then, we identify challenges of 3GPP long term evolution (LTE) in enabling future AMI applications. More importantly, the latest improvements to LTE-A standard release 12 and 13 are reviewed and analyzed with regards to their potential to improve the quality of LTE-enabled AMI. It is found that 3GPP enhancements on machine type communications (MTC) standards will significantly enhance AMI communications. Beyond MTC specifications, non-MTC-specific enhancements such as carrier aggregation and multi-connectivity for user equipment will also contribute greatly to improving reliability and availability of AMI devices. The paper's focus is towards improved backhaul support for innovative and future AMI applications, beyond traditional automatic meter reading.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.273-278
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• 2016

In order to evaluate the lifespan of high-temperature parts with thermal barrier coating in gas turbines used for power generation, this study was performed on an 80 MW-class gas turbine exceeding 24 k equivalent operating hours. Degradation characteristics were evaluated by analyzing the YSZ (Yttria Stabilized Zirconia) top coat, which serves as the thermal barrier coating layer, the NiCrAlY bond coat, and interface layers. Microstructural analysis of the top, middle, and bottom sections showed that Thermal Growth Oxide (TGO) growth, Cr precipitate growth within the bond coat layer, and formation of diffusion layer occur actively in high-temperature sections. These microstructural changes were consistent with damaged areas of the thermal barrier coating layer observed at the surface of the used blade. The distribution of Cr precipitates within the bond coat layer, in addition to the thickness of TGO, is regarded as a key indicator in the evaluation of degradation characteristics.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.279-284
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• 2016

Assessing the handling properties of coal becomes a major issue for the operation of a fuel supply system in power plants, due to the increased types of coal imported into Korea. In this study, the cohesion strengths of 13 bituminous and sub-bituminous coals from different countries were tested by measuring the amount of force that leads to a failure of consolidated particles. The particle size was in the range of 0.1-2.8 mm, which represents the coarse particles before pulverization. While the cohesion strength was proportional to the compression force in the tested range, the effects of the surface moisture content and the weight fraction of fines were crucial for cohesive coals. At fixed conditions of surface moisture and particle size, large variations were found in the cohesion propensity between coals. For coals of 0.1-0.5 mm with the moisture added close to the critical value, cohesive coals had the density over $900kg/m^3$ after consolidation. The cohesion propensity was not correlated with the basic properties of coals with sufficient statistical significance.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.119-122
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• 2020

With recent ESS (Energy Storage System) fire accident, the fault protection performance is becoming more important. However, there has never been any experiments with the protection performance on the faults in the ESS system level. In this study, the effect of AC ground fault and IGBT (Insulated Gate Bipolar mode Transistor) short-circuit failure on MW class ESS was performed experimentally for the first time in the world. First of all, the effect of the AC single line ground fault on battery was analyzed. Moreover, the transient voltage was investigated as a function of the battery capacity and the power level. Finally, the breaking capability and insulation performance of ESS were examined under PCS short-circuit fault condition. Through the tests, it was found that ESS protection system safely blocked the faulty current regardless of the faults, whereas the electronic parts such as IGBT and MC (Magnetic Contactor) were broken by the fault current. Also, the electrical breakdown in ESS resulted from the transient voltage during the protection process.