• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.3
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• pp.175-181
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• 2004

The protection against transient instability and consequent out-of-step condition is a major concern for the utility industry. Unstable system may cause serious damage to system elements such as generators and transmission lines. Therefore, out-of-step detection is essential to operate a system safely. The detection of out-of-step is generally based upon the rate of movement of the apparent impedance. However such relay monitors only the apparent impedance which may not be sufficient to correctly detect all forms of out-of-step and cannot cope with out-of-step for a more complex type of instability such as very fast power swing. This paper presents the out-of-step detection algorithm using voltage frequency deviation. The digital filters based on discrete Fourier transforms (DFT) to calculate the frequency of a sinusoid voltage are used, and the generator angle is estimated using the deviation of the calculated frequency component of the voltage. The proposed out-of-step algorithm is based on the assessment of a transient stability using equal area criterion. The proposed out-of-step algorithm is verified and tested by using EMTP MODELS.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.335-337
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• 2003

The protection against transient instability and consequent out-of-step condition is a major concern for the utility. The unstable system may cause serious damage to system elements such as generators and transmission lines. Therefore, out-of-step detection is essential to operate a system safely. This paper presents the Out-of-Step detection algorithm using voltage frequency variation. The digital filters based on Discrete Fourier Transforms (DFT) to calculate the frequency of a sinusoid voltage are used, and the generator angle is estimated using the variation of the calculated voltage frequency. The proposed out-of-step algorithm is based on the assessment of a transient stability using equal area criterion. The proposed out-of-step algorithm is verified and tested by using EMTP MODELS.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.4
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• pp.537-542
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• 2008

The protection against transient instability and consequent out-of-step condition is a major concern for the utility industry. Unstable system may cause serious damage to system elements such as generators and transmission lines. Therefore, out-of-step detection is essential to operate a system safely. Also, a multi-agent system is one that consists of a number of agents, which interact with one another. Multi-agent systems(MAS) can offer the flexibility and the adaptability to the previous algorithm. In this paper, the detection algorithm of out-of-step is designed by multi-agent system and implemented by EMTP-MODELS. To verify performance of the proposed algorithm based on multi-agent system, simulations by EMTP have been carried out.

• Fire Science and Engineering
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• v.31 no.6
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• pp.112-117
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• 2017

This research discusses the correlation about fire mechanism based on real fire cases. Electric power condenser failure mechanism is classified into 7 steps and fire mechanism is classified into 12 steps. In the 5th step, the procedure of operating a protection channel of a protection relay was identical in the case of the failure and fire. As the fire occurrence mechanism was applied from the 6th step, internal pressure was increased because of gas generation produced by internal combustion phenomenon and arc. This caused explosion in 10st step of fire occurrence mechanism. In 11th step, the flame such as arc gushed out with insulating oil which caused fire and leaded to second accident. This kind of step correlation could play an important part to examine fire.

• The Journal of Fisheries Business Administration
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• v.42 no.2
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• pp.113-130
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• 2011

The laver has been cultivated long time ago by Korea and Japan. Korean Laver Industry has been influenced by Japan on the many factors since 20th. Nevertheless now the both country showed widening disparities across the aspect of total Laver Industry each other. The development steps of Korea and Japan Laver Industry have been advanced differently. That is, we can keep the Laver Industry development steps of both countries separate by 4 steps. But insignificant of every step against both countries has been dissimilar. We can separate from 4 steps in Korea, 1 step is origin period from beginning of laver cultivation to 1961. Next step is First Development period from 1962 to 1978. This period come out production increase from about 10,000 tons early 1960 to 50,000 tons late 1970. Next step is Second Development period from 1979 to 2000. This period come out eminent production increase from about 50,000 tons early 1980 to 200,000 tons late 1990. Next step is Stabilization period from 2001 to now. This period come out production control the size of its production and enlargement of Laver Export. We can also separate from 4 steps in Japan, 1 step is origin period from beginning of laver cultivation to 1944. Next step is Development period from 1945 to 1975. This period come out production increase from about 4 billion sheets early 1960 to 8.5 billion sheets 1975. Next step is Peak period from 1976 to 1982. This period come out sustainable production peak by 6~8 billion sheets and high price. Next step is Decline period from 1983 to now. This period come out production control the size of its production and sustainable price down. These differences showed out facing problems of Korean and Japanese Laver Industry differently. In case of Korea, the facing problems show out 3. First is structural problem, for example, trouble between original laver producer and the finished producer by dry laver products. Second is Insufficiency of Plants Protection System. Third is low quality of Laver. In case of Japan, the facing problems also show out 3. First is sustainable decrease of laver consumption. Second is change of mind against laver, for example, the change of the propensity to consume, and decrease of brand power. Third is Influence of global system. The difference of development steps of Korea and Japan Laver Industry show out 2 point of view to us. First we need consider positive strategy against laver production system of enlargement. Second, we need consider separate strategy against high quality laver and low quality laver.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1466-1473
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• 2017

Generally, electrical torque in synchronous generator is balanced with the rotor mechanical torque under steady-state condition. Thus, the synchronous generator rotor rotates at constant speed. However, under fault condition, the electrical torque output is suddenly decreased and the sum of both torques does not remain constant. If the mechanical torque is not decreased at the same time, the generator rotor would accelerate. Therefore, this accelerating generator rotates at different speeds with respect to other generators in the power system. This phenomena is called as Out-of-Step (OOS). In this paper, we presented a certain two-step type quadrilateral OOS relay setting, which is applicable in actual field, and examined the validity of its setting value with OOS simulation conditions due to delayed fault clearing in transmission line. In order to conduct the study of OOS relay characteristics, we checked the impedance locus and generator output characteristics under the various delayed fault clearing conditions. Moreover, we proposed a countermeasure for avoiding the misoperation of OOS relay during the stable swing by modifying the setting values.

• Journal of the Korean Society of Safety
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• v.19 no.1
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• pp.102-107
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• 2004

Performance based design is a recent evolutionary step in the process of designing fire protection systems. In essence, it is a logical design process resulting in a solution that achieves a specified performance. Sometimes the prescriptive solutions presented in various codes and standards are too expensive or inflexible. Often the solutions do not and enables optimization of a solution for cost and function. In this study, performance based design was carried out to determine the extent of passive fire protection for oil terminal facilities. The results of performance based design were compared with those of prescriptive code based design. Performance based design is not always more economic than prescriptive code based design but provides more reliable and effective design that is fit for the purpose.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.6
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• pp.265-271
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• 2018

DC-DC buck converter is a critical building block in the power management integrated circuit (PMIC) architecture for the portable devices such as cellular phone, personal digital assistance (PDA) because of its power efficiency over a wide range of conversion ratio. To ensure a safe operation, avoid unexpected damages and enhance the reliability of the converter, fully-integrated protection circuits such as over voltage protection (OVP), under voltage lock out (UVLO), startup, and thermal shutdown (TSD) blocks are designed. In this paper, these three fully-integrated protection circuit blocks are proposed for use in the DC-DC buck converter. The buck converter with proposed protection blocks is operated with a switching frequency of 1 MHz in continuous conduction mode (CCM). In order to verify the proposed scheme, the buck converter has been designed using a 180 nm CMOS technology. The UVLO circuit is designed to track the input voltage and turns on/off the buck converter when the input voltage is higher/lower than 2.6 V, respectively. The OVP circuit blocks the buck converter's operation when the input voltage is over 3.3 V, thereby preventing the destruction of the devices inside the controller IC. The TSD circuit shuts down the converter's operation when the temperature is over $85^{\circ}C$. In order to verify the proposed scheme, these protection circuits were firstly verified through the simulation in SPICE. The proposed protection circuits were then fabricated and the measured results showed a good matching with the simulation results.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.4
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• pp.405-412
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• 2013

This paper includes new protection concepts and practices to avoid mechanical damage of three-phase transformer by asynchronous operation of synchronous generator. this failure is often caused just after synchronous generator was connected to the grid because of a malfunction of the controller or misconnections of the synchronous devices. The results of the studies on the analyzing the phenomenon of asynchronous operation experienced in Korea and rapidly detecting asynchronous state are descrived.

• Korean Journal of Materials Research
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• v.8 no.6
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• pp.571-576
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• 1998

This study was carried out for investigating the corrosion behaviors, corrosion mechanisms, and behaviors of elements on a separator for a molten carbonate fuel cell under both the electrolyte and anode side environment. A 310S austenitic stainless steel was used as the separator material. Corrosion proceeded via three steps; the formation step of corrosion product in which rapid corrosion takes place until stable corrosion product is formed after the beginning of corrosion, the protection step against corrosion until breakaway occurs after the formation step of stable corrosion product and the advancing step of corrosion after the breakaway. From the standpoint of the behavior of the elements in the specimen, Fe and Cr, Ni were enriched in the region of corrosion product, in the region of corrosion protection, and at the Cr-deplete zone, respectively. With respect to corrosion mechanism, ionization of electrolyte at the anode side was the main corrosion mechanism, and the final corrosion products were $LiFeO_2$ and $LiCrO_2$ at the anode side.