• Journal of the Korea Convergence Society
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• v.2 no.4
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• pp.21-27
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• 2011

Recently, new distributed power sources such as photovoltaic, wind power, fuel cell systems etc. are energetically interconnected and operated in the distribution feeders, as one of the national projects for alternative energy. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection conditions of new power sources may cause several power quality problems like voltage sag, voltage swell, harmonics, since new power sources can change typical characteristics of distribution systems. Under these situations, this paper deals with the analysis the power quality problems at primary and secondary feeders in distribution systems, when new power sources like photovoltaic (PV) systems are interconnected, by using the test devices for PV systems based on the LabVIEW S/W. This paper presents the test device which is consisted with model distribution system and model PV systems. By performing the simulation for power quality operation characteristic based on the test facilities, this paper presents the optimal countermeasures for power quality.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.122-124
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• 2005

Underground distribution system is a trend due to the successive development of metropolitan area and satellite cities and the environment of the commercial and residential areas. The high quality of electricity, which is related with the minimal outage duration time due to the maintenance work for the underground distribution line, is mandatory. Hence, the construction method and tools for the outage-free maintenance construction have been required for underground distribution system. So far, all the efforts for outage-free maintenance for the underground distribution have been limited only to the survey for foreign countries situation and the theoretical provision; thus, It is required to develop the various construction method and the application tools. Differently from the aerial line, the construction of the underground cable is complicated and the insulation distance between conductor and shield should be maintained in loadmaking/breaking operation, though the apparatus connected with cable is a deadfront type. Also since the apparatus is installed above ground, by-pass of faulted area at busy area needs a variety of high technologies. Therefore, in this these, the authors introduce the development status of the loadbreak connectors, connection facilities, outage-free maintenance system for secondary side, a secondary auxiliary bushing and additional tools so that there can be more progress on this field.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.49-58
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• 2003

Underground flexible pipes for electric cables are subject to external loads and surrounding soil pressure. Particularly, strain of flexible pipes is of great concern in terms of safety and maintenance for electric cables. In this paper, stress and strain of flexible pipes with various installation depth are compared using traditional formula, FEM analysis, model soil box test and field test. from the findings of various analyses, considering the strain criteria-maximum 3.5%, it is suggested that flexible pipes can be buried at the depth of 80cm without additional soil improvement.

• Fire Science and Engineering
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• v.20 no.1 s.61
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• pp.71-76
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• 2006

The major causes of electrical fire are classified to short circuit fault, overload fault, electric leakage and electric contact failure. The occurrence factor of the fire is electric arc or spark accompanied with electrical faults. Residual Current Protective Device(RCD) of high sensitivity type used at low voltage wiring cuts off earth leakage and overload, but the RCD can't cut off electric arc or spark to be a major factor of electrical fire. As the RCDs which are applied low voltage distribution panel are prescribed to rated breaking time about 30[ms](KS C 4613), the RCDs can't perceive to the periodic electric arc or spark of more short wavelength level. To be improved on such problem, this paper is proposed to a auxiliary control apparatus for RCD trip on electric arc or spark due to electrical fire. Some experimental results of the proposed apparatus is confirmed to the validity of the analytical results.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.173-179
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• 2001

This paper represents the control algorithm of the instantaneous voltage sag corrector for the power quality enhancement in distribution line. Especially, a novel detection technique of the symmetrical components is proposed for the analysis of the three-phase unbalanced and asymmetrical problems caused by the single line ground fault which is he most frequent event. This proposed method is based on the simple calculation and the control references of the symmetrical components for voltage compensation can be described as dc value without any other phase detection procedure. And also, for the generation of the reference voltages, the UF and MF defined by IEC is considered. Using this proposed control algorithm, the compensator has the fast dynamic characteristics and the THD of the compensated voltage waveform is very low. Finally, the validity of the proposed algorithm is proved by the PSCAD/EMTDC simulation and experimental results.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.3
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• pp.29-33
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• 2016

Development of the distributed energy resources such as photovoltaic, wind, and fuel cell has increased rapidly due to the rising demand for clean energy utilization. On the other hand, the distribution system became complex and has problems such as degradation of power factor and current unbalance caused by power converters, reactive power and unbalanced loads. To solve these problems, this paper proposes a 3-phase 4-leg type power conditioning system with compensation control algorithm for the reactive power and unbalance current in distribution system using photovoltaic resource. It is simulated in PSCAD/EMTDC and the effectiveness is confirmed.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.5
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• pp.420-429
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• 2004

This paper proposes a novel current control strategy on active power filters using PQR instantaneous power theory which can compensate the line current harmonics and the neutral line current under the unbalanced and/or distorted source conditions in three-phase four-wire systems. The characteristics of the inverter ac filters are analyzed and a novel digital controller are proposed to overcome the inherent time delay problem in digital controllers with designed control gain in this paper. The proposed current control method is based on a sinusoidal PWM for fully-digital implementation compared with a conventional hysteresis PWM. PSiM simulation results verify the good performance of the proposed current control strategy on shunt type APFs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.269-278
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• 2016

In order to maintain customer voltages within allowable limit($220{\pm}13V$) as much as possible, tap operation strategy of SVR(Step Voltage Regulator) installed in distribution system is very important, considering the scheduled delay time(30 sec) of SVR. However, the compensation of BESS(Battery Energy Storage System) during the delay time of SVR is being required because the customer voltages in distribution system interconnected with PV(Photovoltaic) system have a difficultly to be kept within allowable limit. Therefore, this paper presents the optimal voltage stabilization method in distribution system by using coordination operation algorithm between BESS and SVR. It is confirmed that customer voltage in distribution system can be maintained within allowable limit($220{\pm}13V$).

• Fire Science and Engineering
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• v.15 no.1
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• pp.23-33
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• 2001

The utility tunnels are the important facility as a mainstay of country because of the latest communication developments. However, the utilities tunnel is difficult to deal with in case of a fire accident. When a cable burns, the black smoke containing poisonous gas will be reduced. This black smoke goes into the tunnel, and makes it difficult to extinguish the fire. Therefore, when there was a fire in the utility tunnel, the central nerves of the country had been paralyzed, such as property damage, communication interruption, in addition to inconvenience for people. This paper is based on the fire occurred in the past, and reenacting the fire by making the real utilities tunnel model. The aim of this paper is the scientific analysis of the character image of the fire, and the verification of each fire protection system whether it works well after process of setting up a fire protection system in the utilities tunnel at a constant temperature. The fire experiment was equipped with the linear heat detector, the fire door, the connection water spray system and the ventilation system in the utilities tunnel. Fixed portion of an electric power supply cable was coated with a fire retardant coating, and a heating tube was covered with a fireproof. The result showed that the highest temperature was $932^{\circ}c$ and the linear heat detector was working at the constant temperature, and it pointed at the place of the fire on the receiving board, and Fixed portion of the electric power supply cable coated with the fire retardant coating did not work as the fireproof. The heating tube was covered with the fireproof about 30 minutes.

• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.165-172
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• 2015

The class of Dynamic Positioning System is divided in 3 classes depending on its redundancy and reliability according to IMO and classification society. There are 3 DP classes such as DP Class 1, 2 and 3 according to IMO MSC/Circ. 645. Higher DP class vessel has higher reliability, since redundancy concept is applied to the DP vessel depending on its DP class and can operate more safely. There are not enough information about DP class notation, which are needed when a company builds a new or buys second hand DP vessel or modifies DP classes, even the Korean shipyard is building a lot of DP vessels now. Also, the practical case of DP vessel modification, which had been done in Korea, to meet DP notation of IMO and classification society, will be helpful for DP vessel modification and sales industry development in Korea as a new business. As such this research identified what kind of requirements need to be taken into account to be from DP class 1 to DP class 2. The real DP class modification case is used to identify the requirements of DP class upgrade. Through the FMEA the redundancy concept on power system, thruster system and DP control system need to apply for DP class upgrade. The power system have to keep its DP function even if just a single fault happens on the generator or switchboard. Also, the PMS is required to monitor and control power system. Ship's Surge, Sway and Yaw movements can be controlled by the remaining thruster system after a single thruster fails. Lastly, multiple installation of PRS, sensors and DP control system are required to keep DP ability after a single fault on the DP control systems.