• Proceedings of the KIEE Conference
• /
• 2006.07a
• /
• pp.204-205
• /
• 2006

This paper describes the protective ability of lightning arrestor in combined distribution system with power cable. To evaluate the protective ability, change of arrestor and grounding location are considered. On the other hand, arrestor developed by Cooper Power Systems for underground power cable system, is considered to evaluate surge protective ability as in underground system, when arrestor occurs failure has overhead line. The result shows that lightning arrestor in combined distribution system with power cable protect effectively when failure at arrestor in overhead line. On the other hand, arrestor developed by Cooper Power Systems for underground power cable system, is considered to evaluate surge protective ability in underground distribution system, when arrestor of overhead line has failure. The result shows that lightning arrestor installed in underground cable can effectively protected cables from surge when arrestor of overhead line has failure. And also even though grounding locations are decreased, it is revealed that protective ability is nearly similar.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.8
• /
• pp.2064-2070
• /
• 1995

Characteristics of thermal flow stratification were studied experimentally by using the small scale pressurizer-surge line model. Thermal flow stratifications in the horizontal section of surge line were analyzed by the relation between the maximum temperature difference at any cross section in surge line and the Froude number representing the boundary conditions, i.e., in/out surge flow velocity and temperature difference of system. Thermal flow stratifications in outsurge flow decreased inversely proportional to the Froude number and did not exist for Fr>1. In insurge flow thermal flow stratifications disappeared near Fr=1.5, but resulted in the higher temperature difference than the case of outsurge flow.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.208-216
• /
• 2004

The waterhammer occured when the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity. The field tests of the waterhammer were carried out for PanGyo booster pumping station. The PanGyo pumuing station was installed booster pump of 6 sets and in-line pump of 2 sets. The main surge suppression device was equipped with the pump control valve and the surge relief valve as auxiliary. However, the pump control valve had not early controlled in the planned closing mode, and the slamming occurred to the valve of which abruptly closed during the large reverse flow. Because the pressure wave caused by the pump failure was superposed on the slam surge, the upsurge increased so extremely that the shaft of the valve was damaged. After the addition surge suppression device was equipped with air chamber. Further more in-line pump is needed surge suppression device that the pumping station acquired the safety and reliability for the pressure surge.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.276-277
• /
• 2015

As the effect of global warming continues, surge rates in Korea are also getting increased. Although there are devices to protect distribution line from the surge like lightning arrester, insulation of the lightning arrester can be destroyed if frequent surge occurs in distribution line. This paper assumed that the lightning surge hits the lightning arrester and make this device's insulation destroyed. This paper also simulated these processes utilizing EMTP/ATPDraw and verified voltage behavior when faults such as line to ground fault due to frequent lightning surge occur in lightning arrester.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.26 no.2
• /
• pp.78-85
• /
• 2012

Low-Voltage power lines should equip surge protection devices which protect electronic equipments and human lives against lightning and abnormal voltages. Data transmission capacity of the power line is determined by frequency characteristics of the surge protective devices. To analyze the effects of surge protective devices on the data transmission performance, various combinations of installation methods are tested which include ZnO varistor elements that is compatible with class I, class II and class III. The result claims that ZnO varistor for class III is found to be one of the main factors that deteriorates the transmission performance. To overcome this problem a serial connection methed between Gap type SPD and ZnO varistor is proposed. With the proposed scheme, laboratory experimental results show that the data transmission performance can be improved up to 91.9[%] with proper SPD combination.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.8
• /
• pp.1259-1269
• /
• 1997

The procedure for the determination of the residual life of the pressurizer surge line nozzle in the nuclear plant is developed. The design fatigue life for the 1800 $ft^3$ pressurizer surge line nozzle in cast head design is compared with that of Westinghouse stress report, and the percentage difference between two results is less than 9%. The design fatigue life evaluation of the 1000 $ft^3$ pressurizer surge line nozzle in fabricated head design is carried out, and the consuming rate and residual life are estimated using the operating data.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.18 no.5
• /
• pp.132-139
• /
• 2004

Unsymmetrical faults are classified into single line-to-ground faults, line-to-line faults, or double line-to-ground faults in receiving and distribution power systems. Many of overhead distribution-line faults are single line-to-ground faults, and lightning surge arresters are stressed by system frequency overvoltages due to unsymmetrical faults. In this work, the unsymmetrical faults in receiving and distribution systems were experimentally simulated, and the characteristics of total leakage current flowing through lightning surge arresters due to various unsymmetrical faults were investigated. As a result, a little variations of the leakage current flowing through Zinc oxide (ZnO) surge arresters in the range of $\pm$10[%] voltage regulations were observed. It could be concluded that the unsymmetrical faults have no effect on the long-term life performance of ZnO surge arresters in effective grounding systems. On the other hand, the magnitude of the leakage current flowing through ZnO surge arrester elements under single line-to-ground faults was more than 140 times as compared with that under normal operating voltages in ineffective grounding systems. But abnormal voltages caused by line-to-line faults and double line-to-ground faults have a little effect on total leakage current of ZnO surge arrester elements.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.729-734
• /
• 2008

A thermal stratification may occur in the horizontal parts of the surge line during operating transients of the pressurizer, which produces relatively high fatigue usage factor. Heat-up transient is the most severe case among the transient conditions. In this study, to study the relationship between the magnitude of thermal stratification and the length of vertical part of the surge line, some parametric fluid-structure interaction (FSI) analyses with different length variables of the vertical part of the surge line were performed for plant heat-up transient condition by using 3-dimensional numerical analysis. The conservativeness of the traditional finite element model for thermal stratification analysis based on the conservative assumption in the surge line was also discussed by comparison of the results of 3-dimensional transient FSI analysis of this study. Stresses calculated with 3-dimensional transient model were considerably reduced comparing with the traditional analysis.

• Proceedings of the KIEE Conference
• /
• 1997.07e
• /
• pp.1642-1644
• /
• 1997

The simulation study of lightning faults reducing effects by the installation of surge arresters on the 154 kV transmission line is stated here. For the purpose of detailed simulation of arcing horn, a flashover model with dynamic characteristics of arcing horn gap was represented as a non-linear inductance which is controlled by EMTP/TACS(Electromagnetic Transient Program/fransient Analysis of Control Systems) switches. The back flashover inducing current was increased from 50 kA to 88 kA by the installation of surge arresters on the transmission line which has one ground wire and 20 ohms of tower footing resistances. The great advantage of surge arrester installation on one circuit of the double circuit transmission line is to prevent the simultaneous back flashover up to 190 kA.

• Nuclear Engineering and Technology
• /
• v.40 no.3
• /
• pp.239-250
• /
• 2008

If there is a water flow with a range of temperature inside a pipe, the wanner water tends to float on top of the cooler water because it is lighter, resulting in the upper portion of the pipe being hotter than the lower portion. Under these conditions, such thermal stratification can play an important role in the aging of nuclear power plant piping because of the stress caused by the temperature difference and the cyclic temperature changes. This stress can limit the lifetime of the piping, even leading to penetrating cracks. Investigated in this study is the effect of thermal stratification on the structural integrity of the pressurizer surge line, which is reported to be one of the pipes most severely affected. Finite element models of the surge line are developed using several element types available in a general purpose structural analysis program and stress analyses are performed to determine the response characteristics for the various types of top-to-bottom temperature differentials due to thermal stratification. Fatigue analyses are also performed and an allowable environmental correction factor is suggested.