• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.7
• /
• pp.429-434
• /
• 2016

This paper deals with the characteristics of partial discharge (PD) for the purpose of a condition based maintenance (CBM) of gas insulated switchgears (GIS) in power equipment. Four types of electrode systems such as a protrusion on enclosure (POE), a particle on spacer (POS), a free particle (FP) and a Floating were designed and fabricated. PD pulses were measured using UHF sensor with a frequency range of 300 MHz~1.4 GHz and a DAQ with a sampling rate of 250 MS/s. Discharge inception voltage (DIV), discharge extinction voltage (DEV), and phase resolved partial discharge (PRPD) were analyzed depending on electrode systems. The average DIV in the POS was 28.8 kV. It was about 1.7 times higher than that in the FP, which was the lowest value of 17.2 kV. The FP shuffled and jumped at the applied voltage of 23.5 kV. Over 95% of PD pulses in the POE were generated in the negative polarity ($181^{\circ}{\sim}360^{\circ}$) of applied voltage. The results showed the phase (${\Phi}$)-magnitude (dBm) of PD pulses by UHF sensor, a cluster was formed separately depending on electrode systems.

• Fire Science and Engineering
• /
• v.22 no.1
• /
• pp.1-9
• /
• 2008

Carbon dioxide($CO_2$) agent, which has more safely extinguished fire than any other gaseous fire extinguishing agents, has been widely used in various protected enclosures and types of fires. According to the concept of performance-based design(PBD). $CO_2$ extinguishing system to be designed is needed to be evaluated for the performance of fire suppression with possible fire scenarios in an enclosure. In this paper, CFD simulations were carried out to study the effects of opening area on the performance of $CO_2$ extinguishing system and the flow characteristics in the machine room of $100m^3$ in which kerosene spill fire happened. This study showed that time of fire suppression increased linearly in proportion to the size of opening area, and fires for each model were completely suppressed prior to the end of discharge of $CO_2$ agent. It was shown that mass flow rate through opening was influenced by the combined effects of heat release rate of fire and discharge of $CO_2$ agent. After $CO_2$ agent was completely discharged, oxygen concentrations in enclosures for each model were lower than the limit concentration of combustion.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.4
• /
• pp.34-42
• /
• 2016

In order to prepare for the type approval test for the United States Coast Guard (USCG) Phase-II of Ballast Water Treatment System (BWTS), a phytoplankton mass culture was conducted in a mesocosm enclosure. We evaluated the response of the phytoplankton community after nutrient addition (+N, +P, and +NP) and investigated the development of the species with increasing culture time. After nutrient dosing, the phytoplankton population significantly (p < 0.05) increased from day 1 to day 3, depending on the nutrient treatments In particular, the specific growth rate of the phytoplankton community in the case of +NP treatment and + N treatment were estimated to be $2.47d^{-1}$ and $1.98d^{-1}$, respectively. The phytoplankton population density in the case of + NP treatment was approximately 50 times higher than that of the control group, suggesting that these treatments could be useful for mass culturing phytoplankton (> 75% of natural community) for the approval regulation of USCG Phase-II. In the phytoplankton community of the mesocosm, Pseudo-nitzchia spp. dominated in the logarithmic growth phase. The cell density decreased significantly (p < 0.05) with increasing time, coinciding with the nutrient limitation. At that time, the dominance of Pseudo-nitzchia spp. shifted to that of Cylindrotheca closterium. Therefore, the optimum nutrient concentration ($N:30{\mu}M$, $P:3{\mu}M$) and reasonable harvesting time (after 3 days in summer) found in this study for the mass culturing of phytoplankton may be helpful to meet the USCG Phase-II biological criteria to be used in BWTS.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.6
• /
• pp.1274-1279
• /
• 2011

The purpose of this paper is to present the manufacturing defect and damage pattern of a 3 phase 22.9/3.3kV oil immersed transformer, as well as to present an objective basis for the prevention of a similar accident and to secure data for the settlement of PL related disputes. It was found that in order to prevent the occurrence of accidents to transformers, insulating oil analysis, thermal image measurement, and corona discharge diagnosis, etc., were performed by establishing relevant regulation. The result of analysis performed on the external appearance of a transformer to which an accident occurred, the internal insulation resistance and protection system, etc., showed that most of the analysis items were judged to be acceptable. However, it was found that the insulation characteristics between the primary winding and the enclosure, those between the ground and the secondary winding, and those between the primary and secondary windings were inappropriate due to an insulating oil leak caused by damage to the pressure relief valve. From the analysis of the acidity values measured over the past 5 years, it is thought that an increase in carbon dioxide (CO2) caused an increase in the temperature inside the transformer and the increase in the ethylene gas increased the possibility of ignition. Even though 17 years have passed since the transformer was installed, it was found that the system's design, manufacture, maintenance and management have been performed well and the insulating paper was in good condition, and that there was no trace of public access or vandalism. However, in the case of transformers to which accidents have occurred, a melted area between the upper and the intermediate bobbins of the W-phase secondary winding as well as between its intermediate and lower bobbins. It can be seen that a V-pattern was formed at the carbonized area of the transformer and that the depth of the carbonization is deeper at the upper side than the lower side. In addition, it was found that physical bending and deformation occurred inside the secondary winding due to non-uniform pressure while performing transformer winding work. Therefore, since it is obvious that the accident occurred due to a manufacturing defect (winding work defect), it is thought that the manufacturer of the transformer is responsible for the accident and that it is lawful for the manufacture to investigate and prove the concrete cause of the accident according to the Product Liability Law (PLL).

• Fire Science and Engineering
• /
• v.24 no.5
• /
• pp.136-141
• /
• 2010

The purpose of this study is to examine the structure and heat generation mechanism of low voltage switches used to turn on or off the power supply to an indoor lighting system and investigate how the fixtures and movable contacts of the switches are damaged depending on the types of energy sources in order to secure the judgment base for expected PL disputes. Based on the Korean Standard (KS) testing method for incombustibility, this study applied a general flame to the switch. In addition, current was supplied to the switch using the PCITS (Primary Current Injection Test System). The ambient temperature and humidity were maintained at $22{\pm}2^{\circ}C$ and 40~60% respectively while performing the test. It is thought that the switch generated heat due to a defective connection of the wire and clip, insulation deterioration and defective contact of the movable contact, etc. The surface of the switch damaged by the general flame was uniformly carbonized. When the flame source was removed, the fire on the switch was extinguished naturally. From the result obtained by disassembling the switch carbonized by the general flame, it could be seen that fixtures and movable contacts remained in comparatively good shape but the enclosure, clip support, movable contact, indicating lamp, etc. showed carbonization and discoloration. In the case of the switch damaged by overcurrent, the clip connecting the wires, clip support, etc. showed almost no trace of damage, but the fixtures, movable contact, indicating lamp, etc. were severely carbonized. That is, the sections with high contact resistance were intensively damaged and showed a damage pattern indicating that carbonization progressed from the inside to the outside. Therefore, it is possible to judge the initial energy source by analyzing the characteristics of the carbonization pattern and the metal fixtures of damaged switches.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.4
• /
• pp.466-471
• /
• 2007

The purpose of study is to obtain basic but important information for the operation of the greenhouse facility located in the suburb of town. Special emphasis is given on the aspect of energy saving method, which can be easilyapplicable in a practical sense. For this end numerical calculation has been made systematically in order to increase the energy efficiency by the evaluation of the temperature distribution in greenhouse. Major parameters considered are primarily the overall shape of greenhouse together with the various conditions of baffle installion inside greenhouse. Further, the performance of heating system is also carefully compared each other for a number of typical arrangements of heating duct. The performance of the computer program developed in this study is evaluated by the observation of the famous fluid trapping phenomenon occurred in staggered baffle condition in the enclosure of greenhouse. Based on the this study, a number of useful conclusions can be drawn, that is, the installation of baffles are quite effective in energy saving method with a minor modification of facility. Also, it is found that the change of the heating duct system can contribute significantly to the uniform temperature distribution in greenhouse. Further other findings obtained by numerical calculation were not only physically consistent and meaningful but also useful for the determination of optimum condition of practical operation of greenhouse.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.1
• /
• pp.40-45
• /
• 2015

Electrode systems: a protrusion on conductor (POC), a protrusion on enclosure (POE), a crack in epoxy plate and a free particle (FP) were fabricated to simulate insulation defects in a gas insulated switchgear (GIS). $SF_6$ gas was filled in the electrode systems by 3 bar and/or 5 bar, respectively. Partial discharge (PD) pulses were detected through a $50{\Omega}$ non-inductive resistor. A calibration test was carried out according to IEC 60270, and the sensitivity was 0.25 pC/mV. PD pulses were distributed in the phase of $50^{\circ}{\sim}135^{\circ}$ and over 95% of them existed in the phase of $55^{\circ}{\sim}120^{\circ}$ for the POC. PD pulses were distributed in the phase of $230^{\circ}{\sim}310^{\circ}$ and over 90% of them existed in phase of $220^{\circ}{\sim}300^{\circ}$ for the POE. PD pulses occurred in the phase of $40^{\circ}{\sim}60^{\circ}$ and $220^{\circ}{\sim}300^{\circ}$ for the crack, and pulse counts were 25% higher in negative polarity than in positive polarity. PD pulses were distributed in every phase unlike to other three electrode systems and the peak magnitude was measured at $118^{\circ}$ and $260^{\circ}$ for the FP. As described above, PD pulses were observed in positive polarity for the POC, in negative one for the POE, in both one for the crack and the FP. In conclusion, it is expected that the identification rate of defect type can be improved by considering the polarity ratio of PD pulses on the PRPDA method.

• Journal of Korean Society of Forest Science
• /
• v.110 no.4
• /
• pp.543-553
• /
• 2021

This research focused on the investigation of isoprene and terpene emissions from 30 major urban tree species. We conducted sampling using a specific dynamic enclosure system between August and September 2020. Seedlings less than three years old were enclosed in a chamber consisting of a 400 L transparent Tedlar bag. The air-flows from the chamber's outlet were sampled using Tenax-filled sorbent tubes in the presence of standard conditions (temperature: 30℃, PAR: 1,000 μmol/m²/sec). A thermal desorption GC/MS system was used to analyze 38 BVOC compounds (isoprene, monoterpene, sesquiterpene, oxygenated monoterpene, and sesquiterpene). Isoprene emitters included Phyllostachys bambusoides, Quercus serrata, Daphniphyllum macropodum, and Buxus Koreana. Monoterpene emitters included Pinus rigida, Acer pictum subsp. mono, Larix kaempfer, Magnolia denudata, Metasequoia glyptostroboides, Pinus koraiensis, Pinus densiflora, and Abies holophylla. The monoterpene emission profiles were dominated by α-pinene, myrcene, limonene, β-pinen, and sabinene, while caryophyllene and farnesene were the prominent sesquiterpenes. Predominant oxygenated monoterpene compounds were also discovered as pulegone, borneol, menthol, eucalyptol, and nerol, while caryophyllene oxide were the prominent oxygenated sesquiterpenes. Sesquiterpenes and oxygenated sesquiterpenes had relatively lower contributions for all species.

• Journal of Korean Society of Forest Science
• /
• v.111 no.4
• /
• pp.490-501
• /
• 2022

In this study, the isoprene and terpene emissions from 32 major urban tree species were investigated. We conducted sampling using a dynamic enclosure system between June and July 2021. Seedlings aged < three years were enclosed in a chamber consisting of a 400 L transparent Tedlar bag. The air flow from the outlet of the chamber was sampled using Tenax-filled sorbent tubes under standard conditions (temperature: 30°C; PAR: 1,000 μmol/m²/sec). A thermal desorption gas chromatography/mass spectrometry system was used to analyze the following 38 biogenic volatile organic compounds: isoprene, monoterpenes, sesquiterpenes, oxygenated monoterpenes, and oxygenated sesquiterpenes. Isoprene emitters included Quercus mongolica, Salix koreensis, Robinia pseudoacacia, and Salix chaenomeloides. Monoterpene emitters included Pinus strobus, Cedrela sinensis, and Cercis chinensis. The monoterpene emission profiles were dominated by á-pinene, myrcene, camphene, and limonene. The predominant oxygenated monoterpene and oxygenated sesquiterpene were eucalyptol and caryophyllene oxide, respectively. For all species, the contributions of sesquiterpenes and oxygenated sesquiterpenes were relatively low.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.25 no.6
• /
• pp.346-361
• /
• 2013

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2012. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. The conclusions are as follows : (1) The research works on thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and valves, fuel cells and power plants, ground-coupled heat pumps, and general heat and mass transfer systems. Research issues are mainly focused on new and renewable energy systems, such as fuel cells, ocean thermal energy conversion power plants, and ground-coupled heat pump systems. (2) Research works on the heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, and industrial heat exchangers. Researches on heat transfer characteristics included the results for natural convection in a square enclosure with two hot circular cylinders, non-uniform grooved tube considering tube expansion, single-tube annular baffle system, broadcasting LED light with ion wind generator, mechanical property and microstructure of SA213 P92 boiler pipe steel, and flat plate using multiple tripping wires. In the area of pool boiling and condensing heat transfer, researches on the design of a micro-channel heat exchanger for a heat pump, numerical simulation of a heat pump evaporator considering the pressure drop in the distributor and capillary tubes, critical heat flux on a thermoexcel-E enhanced surface, and the performance of a fin-and-tube condenser with non-uniform air distribution and different tube types were actively carried out. In the area of industrial heat exchangers, researches on a plate heat exchanger type dehumidifier, fin-tube heat exchanger, an electric circuit transient analogy model in a vertical closed loop ground heat exchanger, heat transfer characteristics of a double skin window for plant factory, a regenerative heat exchanger depending on its porous structure, and various types of plate heat exchangers were performed. (3) In the field of refrigeration, various studies were executed to improve refrigeration system performance, and to evaluate the applicability of alternative refrigerants and new components. Various topics were presented in the area of refrigeration cycle. Research issues mainly focused on the enhancement of the system performance. In the alternative refrigerant area, studies on CO2, R32/R152a mixture, and R1234yf were performed. Studies on the design and performance analysis of various compressors and evaporator were executed. (4) In building mechanical system research fields, twenty-nine studies were conducted to achieve effective design of mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, renewable energy systems, and lighting systems in buildings. New designs and performance tests using numerical methods and experiments provide useful information and key data, which can improve the energy efficiency of buildings. (5) In the fields of the architectural environment, studies for various purposes, such as indoor environment, building energy, and renewable energy were performed. In particular, building energy-related researches and renewable energy systems have been mainly studied, reflecting interests in global climate change, and efforts to reduce building energy consumption by government and architectural specialists. In addition, many researches have been conducted regarding indoor environments.