• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.1
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• pp.71-81
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• 2005

The main objective of the present study is to investigate the performance characteristics of a ground-source heat pump(GSHP) system with a 130 m vertical and 62 mm nominal diameter U-tube ground heat exchanger. In order to evaluate the performance analysis, the ground-source heat pump connected to a test room with $90\;m^2$ floor area in the Korea Institute of Construction $Technology(37^{\circ}39'N,\;126^{\circ}48'E)$ was designed and constructed. This ground-source heat pump system mainly consisted of ground heat exchanger, indoor heat pumps and measuring devices. The cooling and heating loads of the test room were 5.5 and 7.2 kW at design conditions, respectively. The experimental results were obtained from July 2, 2003 to July 1, 2004. The cooling and heating performance coefficients of the system were determined from the measured data. The average cooling and heating COPs for the system were obtained to be 4.90 and 3.96, respectively. The temperature variations in ground and the ground heat exchanger pipe surface at different depths were also measured.

• Journal of the Korean Solar Energy Society
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• v.34 no.2
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• pp.66-72
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• 2014

Ground source heat pump system can achieve high efficiency of performance by utilizing annually constant underground temperature to provide heat source for space heating and cooling. Generally, the depth of constant-temperature zone under the ground depends on surface heat flux and soil properties. The deeper the ground heat exchanger is installed, the higher the heat exchange rate can be acquired. However, in order to optimally design the system, it is necessary to consider both the installation cost and the system performance. In this study, performance analysis of ground source heat pump system according to the depth has been conducted through the case study.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.500-503
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• 2007

During the COMS system level test, the RF compatibility will be performed in order to verify that there is no issue in RF interface between satellite and COMS ground station, namely SOC (Satellite Operation Center) before the launch. As used for KOMPSAT1, the RF coaxial cable was chosen to be used to connect satellite and SOC with various advantages as compared with ground antennas. As the preparation step, RF cable and required multiplexer were tested in advance. This paper suggests the way for the RF compatibility tests between the satellite and the SOC over RF cable interface and presents the estimated level diagram as the signal power analysis result.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.10
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• pp.73-77
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• 2010

Most accidents occurred in power receiving & transforming facility are ground fault. The quality of power supply is deteriorated since the ground fault is not detected promptly. This paper analyzes the problems about system-grounding type of 2 step power receiving & transforming facility, arrangement of protection relaying scheme and ground-fault protection system of ungrounded system. Then, this paper presents the arranging scheme of system-grounding type to improve power supply reliability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.689-696
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• 2018

System grounding is applied to the neutral point of a power source to secure the from any abnormal voltage and/or grounding fault. System grounding, which is applied mainly in ships is an ungrounded and resistance grounded system. Vessels using the MV power system with 3.3kV, 6.6kV, and 11kV mainly adopt a high resistance grounding system among the resistance grounding systems. The ground fault accounts for 95% of all faults occurring in the electrical system and when a fault occurs, the line-to-ground voltage of the power system is increased excessively, which adversely affects the onboard insulation system. This study analyzed the variation characteristics of the line-to-ground voltage neutral point according to the degree of ground fault in a resistance ground system applied in vessels. For this purpose, the characteristics of the grounding system were first explained, and the modeling of the neutral point potential of the line-to-ground voltage of the resistance grounding system in the vessels was derived. Finally, this study examined how the line-to-ground voltage, line voltage, and neutral point change according to various variable environments through MATLAB simulations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.7
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• pp.37-44
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• 2013

Phase to ground faults are possibly one of the maximum number of faults in power distribution system. During a ground fault the maximum fault current and neutral to ground voltage will appear at the pole nearest to the fault. Distribution lines are consisted of three phase conductors, an overhead ground wire and a multigrounded neutral line. In this paper phase to neutral faults were staged at the specified concrete pole along the distribution line and measured the ground fault current distribution in the ground fault current, three poles nearest to the fault point, overhead ground wire and neutral line. A simplified equivalent circuit model for the distribution system under case study calculated by using MATLAB gives results very close to the ground fault current distribution yielded by field tests.

• KIEAE Journal
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• v.14 no.4
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• pp.127-131
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• 2014

The ground source heat pump (GSHP) system is a kind of the temperature differential energy system using relatively stable underground temperature as heat source of space heating and cooling. This system can achieve higher performance of system than it of conventional air source heat pump systems. However, its superiority of the system performance is different according to installation location or local climate, because the system performance depends on the underground condition which is decided by annual average air temperature. In this study, in order to estimate the feasibility of the ground source heat pump system according to the local climate, numerical simulation was conducted using the ground heat transfer model and the surface heat balance model. The case study was conducted in the condition of Seoul, Daejeon, and Busan, In the result, the heat exchange rate of Busan was 34.33 W/m as the largest in heating season and it of Seoul was 40.61 W/m as the largest in cooling.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.2
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• pp.16-26
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• 2014

After the GBAS ground system installing at the airport, a GBAS ground and flight testing must be conducted to verify functionality and performance of the system. Since Korea has no experience of the GBAS ground system installation, GBAS test and evaluation methods have never been studied so far. Therefore this paper analyzes the test items and methods for the GBAS ground and flight testing based on ICAO documents, FAA flight inspection manual and testing reports of other countries. As a result of the analysis, this paper proposes the GBAS ground and flight testing items in korea, also describes the flight procedures for the GBAS flight testing.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3142-3147
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• 2008

A simple transient simulation of ground source heat pump system was carried out to investigate the effects of ground thermal conductivity on its performance. The TRNSYS code with a simple water to water heat pump model was used to compare the COP variation of the system. A new ground heat exchanger called by semi-closed loop was proposed and constructed in the real site. The effective thermal conductivity was measured using the test equipment developed by according to the line source model. The simulation results showed that highly efficient thermal conductivity of the grout material could increase the performance of the heat pump system very well. And the new ground heat exchanger showed the increased effective thermal conductivity as the penetration water flow rate(PWFR) was increased. Therefore, the performance improvement of the heat pump system using the proposed ground heat exchanger can be expected.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.8
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• pp.443-449
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• 2013

The purpose of this study is to propose an enhanced variable-speed control method of ground-water circulation pumps using inlet and outlet ground-water temperature difference and analyze its effect for the ground source multi-heat pump system installed in a single-family house. As a result, it has shown to significantly reduce the electricity use of ground-water circulation pump and improve overall system Coefficient of Performance (COP) due to the proposed variable-speed control under partial load conditions after oversized and inefficient single-speed pump retrofit.