• Transactions of the Korean hydrogen and new energy society
• /
• v.9 no.2
• /
• pp.53-64
• /
• 1998

Thermal analysis on a Linde-Hampson hydrogen liquefaction system using cryogenic refrigerators as precooling has been carried out. Three commercially available models of cryogenic refrigerators, such as CTI l020CP, CVI CGR009 and CVI CGR011, are considered in the performance analysis. The effect of ortho-para conversion process during hydrogen liquefaction is also studied in detail. The results obtained indicate that the optimal hydrogen mass flow rate and the optimal compressed pressure exist for the maximum hydrogen liquefaction rate. The optimal compressed pressure is increased in the range of 80 - 120 bar with an increase in the hydrogen mass flow rate. It is also found that better performance could be obtained with a cryogenic refrigerator, which produces high cooling capacity at precooling temperature in the range of 80 - 100 K.

• Proceedings of the KIEE Conference
• /
• 1995.11a
• /
• pp.77-79
• /
• 1995

In performing lightning and fault studies in GISs, it is of great importance to accurately model the conductor network consisting of the grounding systems and overhead conductor structures. In particular, the overhead grounded pipe enclosures of the GIS should be appropriately modelled. In this paper, the overhead pipe enclosures of a 500 kV $SF_6$ breaker and substation grounding system are presented in detail. During a phase-to-ground fault, scalar potentials and electromagnetic fields are computed at different frequencies for various conductor network configurations is defined by varying the number of conductors used to represent the pipes at different frequencies are obtained. Such knowledge will be very useful in reducing computation time for a transient ground potential rise study which will be performed in the future.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.113-120
• /
• 1990

This paper presents a new aggregation method of induction motors for the load flow and transient stability analysis. The proposed method aggregates a group of motors into a single motor considering the variations of the system voltage and frequency so that the aggregated model represents the dynamic characteristics of the system accurately. The performance of the Method is shown by numerical simulation and is compared with that of LOADSYN algorithm.

• Proceedings of the KIEE Conference
• /
• 2001.07a
• /
• pp.168-170
• /
• 2001

This paper presents the strategy of reactive power compensation which directly improves voltage stability. Voltage stability index that serves as an indirect assessment of voltage stability margin is derived from M.G.C.F. (Modified Generalized Curve Fit) algorithm incorporating load model. Weak buses are ranked by this stability index, and amounts of reactive power compensation are determined by function of reactive power and stability index. Using the proposed strategy, all load buses can be prevented from voltage collapse gradually. A simple illustrative example is given as well as simulation results obtained on 5 bus test system and 19 bus real power system.

• Proceedings of the KIEE Conference
• /
• 1993.07a
• /
• pp.82-85
• /
• 1993

The load forecasting has been essential in planning and operation of power systems. The load composition rata is also needed to analyze power-systems - load flow calculation and system stability. This paper proposes the monthly peak load forecasting methods for load groups in residential class using load composition rate and electric consumption characteristics. The proposed methods were applied to a real-scale power system and the effectiveness was turned out.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.298-300
• /
• 1998

The superconducting magnetic energy storage (SMES) system which has characteristics of high efficiency and rapid response is a way to maximize a utility's generation and transmission capacity. But SMES is required for much capital and operating cost. Therefore, It is important to determine the optimal size of SMES for constructing and operating. In this paper, we proposed a method of determinating an optimal size of a large scale of SMES for energy storage and a small scale of SMES for stabilizing power system.

• Proceedings of the Korean Information Science Society Conference
• /
• 2007.06a
• /
• pp.264-265
• /
• 2007

• 제어로봇시스템학회:학술대회논문집
• /
• 2002.10a
• /
• pp.57.5-57
• /
• 2002

$\textbullet$ Introduction $\textbullet$ Configuration of the ENG System $\textbullet$ Calibration of ENG system $\textbullet$ Algorithm $\textbullet$ Experiment and result $\textbullet$ Conculsion

• Journal of the Korean institute of surface engineering
• /
• v.31 no.1
• /
• pp.54-62
• /
• 1998

In this study, the behaviorof ion nitriding of AISI 304 stainless steel was investigated using plasma ion nitriding system. The characteristics of ion nitriding, and their micsoctrucyures, and physical properties were investigated as a function of process parmeteds. important conclusions can be summarzied as follows. Firstly, it was found that growth of nitride layer in ion nitriding are mainly affected by N2 partial pressures and nitriding temperatures for AISI 304 stainless steel. The $N_2$<\TEX> partial pressure plays on important role in ion nitriding since it determiness the incoming flux of nitrogen species onto specimen surface. Nitriding thmprrature is also important besauseit determines the diffusion rates of nitrogen through nitride layers. While both parameters affects the characteristics rateding are controlled by nitridingen diffusion nitration profiles of N and alloying elements such as Cr and Ni are observed through niride layers. Secondly, nitride layer consists of the upper white laywe having various nitride phases and the underneath diffusion layers. The thickness of white layer increases with $N_2$<\TEX> partial pressures and nitriding temperatures. The thinkness of diffusion layer is increasting nitriding temperatures. Finally, nitriding of stainless steels steel show slighly low their corrsionce prorerties. However, passivation properties, which is normally observed in stainless steels, were still observed aftre ion nitriding.

• Proceedings of the Korean Nuclear Society Conference
• /
• 2004.10a
• /
• pp.1419-1420
• /
• 2004