• Journal of the Korean Society of Safety
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• v.26 no.5
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• pp.41-45
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• 2011

The fire event occurred in fire proof zone often causes serious electrical problems such as shorts, ground faults, or open circuits in nuclear power plants. These would be directed to the loss of safe shutdown capabilities performed by safety related systems and equipments The fire event can treat the basic design principle that safety systems should keep their functions with redundancy and independency. In case of a cable fire, operators can not perform their mission properly and can misjudge the situation because of spurious operation, wrong indication or instrument. These would deteriorate the plant capabilities of safety shutdown and make disastrous conditions. In this paper, the cables of the representative nuclear power plant in korea is selected and the cable functional failure temperature by exposed fire using Cable Response to Live Fire(CAROLFIRE) is studied. It is expected that the results are very useful to know the cable failure temperature by exposed fire. We confirmed the safety and integrity of the cable by exposed fire and those results will use the based data of cable exposed fire characteristics.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.943-946
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• 2018

본 논문은 공공데이터 API를 활용한 ITS(Intelligent Transport System)를 구현하여, 버스 승하차 관련 문제를 개선하는 버스 승하차 사전 알림 시스템에 관한 것이다. 수도권 및 대도시 전체 버스 관련 민원신고 중 가장 많이 차지하는 부분이 버스의 정류장 무정차 통과 및 승차거부 문제다. 이를 해결하기 위해 사전에 승객의 승하차 여부를 버스 운전사에게 미리 알리는 시스템을 제안한다. 이 시스템은 승객용 애플리케이션, 중앙 서버 그리고 버스에 설치되는 디바이스로 구성되어 있으며 예비 승하차 승객이 애플리케이션을 이용하여 자신이 원하는 버스에 대한 정보를 MQTT Broker를 이용하여 서버에 보내고 서버는 해당 버스의 정보와 현재 노선의 운행 현황을 주기적으로 확인하여 요청 정류장 이전에 도달하였을 때 버스 운전자 측 디바이스에 신호를 보내어 버스 운전자가 예비 승하차 승객이 있음을 사전에 알 수 있게 한다. 이 시스템을 통해 무정차 및 승차거부 문제를 근본적으로 해결하여 사용자 편의 승객 안전 일반 차량 운전자 안전 도로 교통 안정화를 도모한다.

• Journal of Internet Computing and Services
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• v.10 no.6
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• pp.37-50
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• 2009

In this paper, we proposed a mechanism for effective cooperation in sensor network. There are a few mechanism like RBS, TPSN, FPSN for sensor network. However these are supporting synchronization among nodes without global state. Therefore, we proposed SGSM(Simple Global State Management) to maintain global state among sensor nodes. As experimental results, we confirmed loss rate is within 1% as maintaining global state with SGSM mechanism. In this paper, we defined global state in sensor network and introduced SGSM for improving timming accuracy in sensor environment.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.22-30
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• 2019

In 2018, overload, overcurrent, insulation aging, and a contact failure caused 659 electric fires. There is almost no failure of electrical socket outlets during their manufacturing or installation period. After several months or several years, overload or overcurrent of electrical socket outlets leads to a contact failure or short circuit which causes an electric fire. Therefore, this paper analyzed for thermal characteristics based on a current value and the change in insulation resistance along with a temperature rise caused by electrical socket outlets and the state of laboratory use in workplaces. As a results, regarding the thermal characteristics based on the current value of each installation year, a temperature increase was related to a current value, an installation year, and whether the contact unit is corroded. Insulation resistance began to decrease when a temperature increased to a certain level. With a lapse of installation year, the temperature at which insulation resistance began to decrease was lowered. This paper can be applicable for the survey data about electrical socket outlet induced fire accidents and management guidelines.

• Journal of the Korean Society of Safety
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• v.34 no.3
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• pp.8-14
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• 2019

Many electrical socket-outlet fire accidents take place not only in homes but in the offices each year. The causes are mostly faulty constructions, managerial problems and carelessness. Construction and managerial flaws can be resolved by regular or special inspections, but carelessness is not solvable through inspections. Such carelessness can be related to the consumption capacity of electrical socket-outlets presently, the rated current of electrical socket-outlets is based on 16A. However, even at 16A, the heat generated in the insulator of an electrical socket-outlet varies due to such factors as part damage and environmental conditions of use. To explore this situation, the study conducted an experiment to analyze thermal relationship by applying 10A, 20A, and 30A currents. To secure reliability, the study employed thermal analysis simulation and compared the thermal relationship in the same current value. The experimental and simulation values were found to be similar and therefore, diverse current values were replaced with the simulation. At 30A, the temperature was found to rise to at least $169.9^{\circ}C$ which had worked as a sufficient amount of energy to bring the insulation aging of insulator.

• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.21-26
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• 2019

This paper is purposed to develop hardware for controlling abnormal temperature that can occur environment and component itself in PCS. In order to be purpose, the hardware which is four part(sensing, PLC, monitoring and output) keep detecting temperature for critical components of PCS and can control the abnormal temperature. Apply to the hardware, it is selected to PV power generation facilities of 20 kW in Cheong-ju city and measured the data for one year in 2017. Through the temperature data, it is found critical components of four(discharge resistance, DC capacitor, IGBT, DSP board) and entered the setting value for operating the fan. The setting values for operating the fan are up to $130^{\circ}C$ in discharge resistance, $60^{\circ}C$ in DC capacitor, $55^{\circ}C$ in IGBT and DSP board. The hardware is installed at the same PCS(20 kW in Cheong-ju city) in 2018 and the power generation output is analyzed for the five days with the highest atmospheric temperature(Clear day) in July and August in 2017 and 2018 years. Therefore, the power generation output of the PV system with hardware increased up to 4 kWh.

• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.14-20
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• 2019

This paper presents a safety assessment based approach for the safe operation for PCS(Power Conditioning System) of photovoltaic and energy storage systems, applying FTA. The approach established top events as power outage and a failure likely to cause the largest damage among the potential risks of PCS. Then the Minimal Cut Set (MCS) and the importance of basic events were analyzed for implementing risk assessment. To cope with the objects, the components and their functions of PCS were categorized. To calculate the MCS frequency based on IEEE J Photovolt 2013, IEEE Std. 493-2007 and RAC (EPRD, NPRD), the failure rate and failure mode were produced regarding the basic events. In order to analyze the top event of failure and power outage, it was assumed that failures occurred in DC breaker, AC breaker, SMPS, DC filter, Inverter, CT, PT, DSP board, HMI, AC reactor, MC and EMI filter and Fault Tree was drawn. It is expected that the MCS and the importance of basic event resulting from this study will help find and remove the causes of failure and power outage in PCS for efficient safety management.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.1
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• pp.17-24
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• 2021

In this study, Ti-X (X=Mn, Fe, Mo) powder alloys were designed and manufactured by both powder metallurgy (PM) and metal powder injection molding (MIM) process to improve strength and formability compared to CP-Ti powder materials. It was found that the lamellar microstructure consisted of α and β phases was formed in PM-processed alloys. However, MIM-processed alloys showed not the lamellar microstucture but the equiaxed α + β microstructure. It was also revealed that the contents of X component and feedstock were not affected to microstructure evolution. The reason why different microstructure was appeared between PM-processed and MIM-processed alloys is not clear yet, but supposed to be the effect of intersticial elements such as C, H and N derived from feedstock during debinding process of MIM.

• Journal of the Korean Society of Safety
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• v.37 no.2
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• pp.69-75
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• 2022

Fire-alarm systems are safety equipment that facilitate rapid evacuation and early suppression in case of fire. It is highly desirable that fire-alarm systems have low false-alarm rates and are thus reliable. Until now, researchers have attempted to improve detector performance by applying new technologies such as IoT. To this end, IoT-based fire-detection systems have been developed. However, due to scarcity of large-scale operational data, researchers have barely studied malfunctioning in fire-alarm systems or attempted to reduce false-alarm rates in these systems. In this study, we analyzed false-alarm rates of smoke/temperature detectors and unwanted fire-alarm signal patterns at K institution, where Korea's largest IoT-based fire-detection system operates. After analyzing the fire alarm occurrences at the institution for five years, we inferred that the IoT-based fire-detection system showed lower false-alarm rates compared to the automatic fire-detection equipment. We analyzed the detection pattern by dividing it into two parts: normal operation and unwanted fire alarms. When a specific signal pattern was filtered out, the false-alarm rate was reduced to 66.9% in the smoke detector and to 46.9% in the temperature detector.

• Journal of the Korean Society of Safety
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• v.37 no.3
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• pp.16-23
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• 2022

This study aims to provide a fundamental material for identifying fire and no-fire signals using the detection signal characteristics of IoT-based fire-detection systems. Unlike analog automatic fire-detection equipment, IoT-based fire-detection systems employ wireless digital communication and are connected to a server. If a detection signal exceeds a threshold value, the measured values are saved to a server within seconds. This study was conducted with the detection data saved from seven fire accidents that took place in traditional markets from 2020 to 2021, in addition to 233 fire alarm data that have been saved in the K institute from 2016 to 2020. The saved values demonstrated variable and continuous VC-Signals. Additionally, we discovered that the detection signals of two fire accidents in the K institution had a VC-Signal. In the 233 fire alarms that took place over the span of 5 years, 31% of smoke alarms and 30% of temperature alarms demonstrated a VC-Signal. Therefore, if we selectively recognize VC-Signals as fire signals, we can reduce about 70% of false alarms.