IEC 60364의 접지방식에 기반한 안전성 평가 시험장치의 모델링 및 구현에 관한 연구

김순식(Soon-Sik Kim),한병길(Byeong-Gill Han),이후동(Hu-Dong Lee),페레이라 마리토(Marito Ferreira),노대석(Dae-Seok Rho) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.6

국내 접지방식은 2021년부터 IEC 60364에서 제시하는 접지방식을 새롭게 채택하고 있다. 이 접지방식은 인체접촉사고 발생 시, 접촉전압과 통과전류에 대한 특성이 다양하게 나타날 수 있어, 인체에 대한 안전성 평가가 구체적으로 요구되고 있다. 또한, 한국전기안전공사나 대한전기협회에서 IEC 60364의 접지방식에 대한 안전기술 교육을 부분적으로 수행하고 있지만, 안전성을 평가할 수 있는 시험장치가 미흡하여, 전기안전관리자에 대한 교육이 어려운 실정이다. 따라서, 본 논문에서는 IEC 60364의 접지방식별 안전성 평가를 수행할 수 있는 시험장치를 모델링하고, 이를 바탕으로 시험장치를 구현한다. 즉, 전력계통 상용해석 프로그램인 PSCAD/EMTDC를 이용하여, 계통 전원부, 접지방식별 시험장치부, 보조장치부로 구성된 안전성 평가 시험장치의 모델링을 제시하고, 계통전원부, TT접지방식 시험장치부, TN-S접지방식 시험장치부, 모니터링부로 구성된 안전성 평가 시험장치를 구현한다. 상기의 모델링과 시험장치를 이용하여, TT접지방식과 TN-S접지방식의 인체 안전성 특성을 분석한 결과, TT접지방식의 경우 고장점 임피던스가 0[Ω], 10[Ω], 100[Ω]에서 인체 통과전류는 각각 104[㎃], 87.4[㎃], 35.5[㎃]가 산정되었고, TN-S접지방식의 경우 54.9[㎃], 4.1[㎃], 0.4[㎃]가 산정됨에 따라, TN-S접지방식이 TT접지방식에 비하여 감전에 대한 보호가 우수함을 알 수 있고, 저압수용가에서 사용 중인 TT 접지방식에서 TN-S 접지방식으로 전환하면 감전에 대한 보호성능을 향상시킬 수 있음을 알 수 있었다. A novel grounding system, which is presented in IEC 60364, has been adopted since 2021. A safety evaluation for the hu㎃n body on the grounding system is required due to the various characteristics of the touch voltage and current passing when the human body experiences an electric shock. The Korea Electrical Safety Corporation (KESCO) and Korea Electric Association (KEA) have been conducting a safety technical education on the grounding system. On the other hand, it is difficult to instruct the electrical safety manager because of a lack of safety evaluations for the test equipment on the grounding system. Therefore, this paper modeled and implemented a test device for a safety evaluation depending on the grounding system of IEC 60364. Namely, this paper presents the modeling of the test device for a safety evaluation using PSCAD/EMTDC S/W, which is composed of an AC grid section, s test device section on the grounding system, and a sub-device section. This paper implemented a test device for safety evaluation, which consisted of an AC grid section, TT grounding system section, TN-S grounding system section, and monitoring section. From the simulation and test results with the safety characteristics of the hu㎃n body in the TT and TN-S grounding system, when the fault impedances are 0[Ω], 10[Ω], and 100[Ω], the currents passing through the hu㎃n body in the TT grounding system are 104[㎃], 87.4[㎃], and 35.5[㎃], respectively. The corresponding currents in the TN-S grounding system are 54.9[㎃], 4.1[㎃], and 0.4[㎃], respectively. Based on the results, the protection performance for an electric shock to the hu㎃n body in the TN-S system is better than the TT system. This can be improved when the existing grounding system is changed from the TT system to the TN-S system.

섬유강화 고분자 복합판의 기계적 성질에 미치는 섬유길이와 섬유함유율의 영향

이상동,김혁,허업,최종대,이동기 조선대학교 에너지.자원신기술연구소 1997 에너지·자원신기술연구소 논문지 Vol.19 No.2

This paper describes effect of chopped strand length fiber content and moisture absorption on mechanical properties of fiber-reinforced polymeric composites. It was extrusion compounded long fiber-reinforced polypropylene containing 20, 30 and 50 percent and short fiber-reinforced ABS and PAS containing 30 percent b37 the weight of glass fiber. The test methods of ASTM D638, D3410-87 and D79OM are applied for tensile, compressive and bending tests respectively. The results show that, in the case of 0.2% moisture absorption, the residual strength decreases dramatically.

급성심근경색후 발생한 심실중격결손 2례

김태희,이재호,김애란,허민영,문치숙,정수룡,김대경,김두일,김동수 인제대학교 백병원 2002 仁濟醫學 Vol.23 No.4

Ventricular septal defect remains an infrequent but devastating complication of acute MI. Approximately 1∼3% of cases of acute myocardial infarction are complicated by ventricular septal rupture in the prethrombolytic era and the incidence has decreased to 0.2% with reperfusion therapy. This mechanical complication usually occurs within the first 10 to 14 days when necrotic tissue is most abundant and the collateral coronary circulation is not well developed. This lesion is generally associated with complete coronary obstruction rather than severe stenosis. Rupture of the ventricular septum is a severe mechanical complication of acute myocardial infarction, usually resulting in death unless surgical repair is performed. The bad prognosis of this event within the first 2 weeks indicates the need for early surgical rapair. This complication is more frequent after the first acute myocardial infarction in the elderly and secondary to a transmural myocardial infarction. We report two cases of ventricular septal rupture after acute myocardial infarction.

3차원 전산화단층촬영 영상을 이용한 얼굴 연조직 두께 계측

정호걸,김기덕,한승호,신동원,허경석,이제범,박혁,박창서 대한구강악안면방사선학회 2006 Imaging Science in Dentistry Vol.37 No.1

Purpose : To evaluate accuracy and reliability of program to measure facial soft tissue thickness using 3D computed tomographic images by comparing with direct measurement. Materials and Methods : One cadaver was scanned with a Helical CT with 3 mm slice thickness and 3 mm/sec table speed. The acquired data was reconstructed with 1.5 mm reconstruction interval and the images were transferred to a personal computer. The facial soft tissue thickness were measured using a program developed newly in 3D image. For direct measurement, the cadaver was cut with a bone cutter and then a ruler was placed above the cut side, The procedure was followed by taking pictures of the facial soft tissues with a high-resolution digital camera. Then the measurements were done in the photographic images and repeated for ten times. A repeated measure analysis of variance was adopted to compare and analyze the measurements resulting from the two different methods. Comparison according to the areas was analyzed by Mann-Whitney test. Results : There were no statistically significant differences between the direct measurements and those using the 3D images (p>0.05). There were statistical differences in the measurements on 17 points but all the points except 2 points showed a mean difference of 0.5 mm or less. Conclusion : The developed software program to measure the facial soft tissue thickness using 3D images was so accurate that it allows to measure facial soft tissues thickness more easily in forensic science and anthropology. (Korean J Oral Maxillofac Radiol 2006; 36 : 49-54)

Research Paper : Allelopathic effect of the root exudates of K21, a potent allelopathic rice

( Hu Won Lee ),( Sita Ram Ghimire ),( Dong Hyun Shin ),( In Jung Lee ),( Kil Ung Kim ) 한국잡초학회 2008 Weed Biology and Management Vol.8 No.2

Operation Strategy of CVCF Inverter-based Micro-grid System Considering Energy Sinking

Lee Hu-Dong,Ferreira Marito,Tae Dong-Hyun,Lee Il-Moo,Rho Dae-Seok 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.3

For the purpose of reducing carbon dioxide (CO 2 ) emissions on island areas, operation methods of constant voltage and constant frequency (CVCF) inverter-based micro-grid(MG) system are being studied by replacing diesel generator with renewable energy sources (RES). However, in the operation of CVCF inverter-based MG system, phenomenon of energy sinking can be occurred when the total output power of RES is greater than total customer loads in inverter-based off -grid MG system. Where, the voltage of the battery system in CVCF inverter to form MG system can rapidly increase depending on the SOC(state of charge) condition, and then blackout in the entire MG system might be occurred due to the shut-down of CVCF inverter. Therefore, in order to overcome these problems, this paper presents transient operation algorithm based on 3 operation modes such as non-critical transient mode, critical transient mode and restoration mode, in order to prevent the shut-down of CVCF inverter with the energy sinking phenomenon in advance. Based on the proposed algorithm, this paper performs the modeling of 30 kW CVCF inverter-based MG system using PSCAD/EMTDC. From the simulation results based 3 operation modes, it is confi rmed that the shut-down of the CVCF inverter can be prevented in advance according to operation conditions of SOC and voltage of the battery system in a CVCF inverter.

Engineering Electronic Properties of Graphene by Coupling with Si-Rich, Two-Dimensional Islands

Lee, Dong Hyun,Yi, Jaeseok,Lee, Jung Min,Lee, Sang Jun,Doh, Yong-Joo,Jeong, Hu Young,Lee, Zonghoon,Paik, Ungyu,Rogers, John A.,Park, Won Il American Chemical Society 2013 ACS NANO Vol.7 No.1

<P>Recent theoretical and experimental studies demonstrated that breaking of the sublattice symmetry in graphene produces an energy gap at the former Dirac point. We describe the synthesis of graphene sheets decorated with ultrathin, Si-rich two-dimensional (2D) islands (<I>i.e.</I>, Gr:Si sheets), in which the electronic property of graphene is modulated by coupling with the Si-islands. Analyses based on transmission electron microscopy, atomic force microscopy, and electron and optical spectroscopies confirmed that Si-islands with thicknesses of ∼2 to 4 nm and a lateral size of several tens of nm were bonded to graphene <I>via</I> van der Waals interactions. Field-effect transistors (FETs) based on Gr:Si sheets exhibited enhanced transconductance and maximum-to-minimum current level compared to bare-graphene FETs, and their magnitudes gradually increased with increasing coverage of Si layers on the graphene. The temperature dependent current–voltage measurements of the Gr:Si sheet showed approximately a 2-fold increase in the resistance by decreasing the temperature from 250 to 10 K, which confirmed the opening of the substantial bandgap (∼2.5–3.2 meV) in graphene by coupling with Si islands.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-1/nn304007x/production/images/medium/nn-2012-04007x_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn304007x'>ACS Electronic Supporting Info</A></P>

Operation Algorithm of Protection Coordination for Isolating Fault Section in Radial MVDC Distribution System

Lee Hu-Dong,Han Byeong-Gill,Choi Sung-Moon,Kang Seong-Hyun,Rho Dae-Seok 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.3

Generally, the existing AC distribution system adopts a protection coordination method using the T-C characteristic curve. However, unlike the method which has coordination time interval with tens ~ hundreds of milliseconds, the protection devices in DC distribution system rapidly operate within several milliseconds, so that it is diffi cult to ensure a protection coordination time interval between protection devices. In order to overcome this issue, this paper proposes operation algorithm of protection coordination in radial MVDC distribution system to rapidly isolate fault sections by using slope characteristics of fault currents and presents prevention method for shutdown of the main power source based on the CLR (current limit resistor). And also, this paper performs modeling of 20 kV-scaled MVDC distribution system, which is composed of substation, main and section converter, based on the PSCAD/EMTDC S/W. From the simulation results of fault characteristics at primary and secondary side in MVDC, it is confi rmed that the main converter in primary feeder cannot be shut down due to keeping fault currents within allowable limits of main converter, if the proper capacity of the CLR is installed at secondary side of section converter. In addition, it is found that the proposed method can isolate outage sections in primary feeder and minimize them, if slope ranges of fault current are properly determined at each protection section.

Evaluation Method for Hosting Capacity of PV System in Distribution System with Micro Hydropower Generator

Hu-Dong Lee,Dong-Hyun Tae,Ji-Myung Kim,Dae-Seok Rho 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.6

According to the Korean government’s policy to demonstrate and expand renewable energy sources, distributed generators such as photovoltaic (PV) and wind power (WP) systems are energetically installed and operated in distribution systems. However, there are many issues related to power quality problems including an over-voltage phenomenon when the PV systems were interconnected and operated. In order to overcome these problems the electric power company has installed the step voltage regulator (SVR) in primary feeders interconnected with PV systems, and also has established technical guidelines for distributed generators to stabilize the customer voltages. However, despite such voltage regulators and technical guidelines, it is diffi cult to maintain the customer voltages within the allowable voltage limit. In order to actively host a large-capacity PV system, this paper proposes an optimal voltage control algorithm of micro hydropower generator (MHG) to keep customer voltages within the allowable voltage limit and presents an evaluation algorithm for hosting capacity of PV system based on a sensitivity analysis method. Furthermore, this paper performs PSCAD/EMTDC modeling based on the proposed algorithm and analyzes characteristics of customer voltages based on various scenarios related to the location and capacity of the PV system and MHG. From the simulation results, it is confi rmed that the proposed methods can contribute to the stabilization of the customer voltages and improve the hosting capacity of the PV system in a distribution system.

PSCAD/EMTDC에 의한 대규모 아파트단지의 접지특성 해석에 관한 연구

이후동(Hu-Dong Lee),신명기(Myeong-Ki Shin),최성식(Sung-Sik Choi),강민관(Min-Kwan Kang),남양현(Yang-Hyun Nam),노대석(Dae-Seok Rho) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.12

건물의 접지방식은 사고 발생 시 고장전류를 대지로 안전하게 방전시켜 인체와 기기의 안전성을 확립하기 위한 중요한 요소이다. 특히, 우리나라 아파트단지의 접지방식은 일본의 영향을 받아 TT접지방식으로 설계/시공되고 있지만, 전기안전을 확보하기 위하여 각동의 건물에서 기초 콘크리트 접지를 시설하고, 이들을 서로 연결하여 수변전실의 변압기 2차측 접지까지 연결하고 있다. 이러한 공동구로 연결된 TT접지방식은 TN접지방식에 가까우므로 1선 지락사고시 사고전류의 크기와 대지전압의 크기가 크게 증가하므로, 이를 정확하게 해석하여 사고에 대한 보호대책을 세우는 것이 중요한 과제로 대두되고 있다. 따라서, 본 논문에서는 대규모 아파트단지의 접지특성을 해석하기 위하여, 도면과 현장측정에 의한 사례분석과 PSCAD/EMTDC의 모델링에 의한 접지방식 특성을 분석하여, 대규모 아파트단지의 접지방식(TN접지방식과 TT접지방식)에 대한 정확한 유형을 파악한다. 또한, 공동구 연결유무에 의한 대규모 아파트단지의 접지방식 구조에 따른 사고해석 알고리즘을 제시하고, 사고발생시 접지계통에서의 접촉전압 및 보폭전압을 고려한 접지계통설계 알고리즘을 제안하였다. 본 논문에서 제시한 모델링과 알고리즘을 바탕으로 실 계통의 아파트단지에 적용한 결과, 대규모 아파트단지의 접지특성 해석에 유용함을 확인하였다. A grounding system in a large-scale apartment complex consists of a TT grounding system when viewed in each building unit, but the characteristics of TN grounding system appears when viewed in the total ground system function. Therefore, this study examined the characteristics of a grounding system in a large-scale apartment complex using design draft, field measurements and PSCAD/EMTDC modeling. This paper proposes an algorithm for fault analysis depending on the grounding system structure in large-scale apartment complexes considering the connection of the underground culvert as well as a design algorithm for each grounding system considering the contact voltage and step voltage. The simulation results based on the proposed modeling and algorithm confirmed that it is useful for analyzing the characteristics of a grounding system in a large-scale apartment complex.