• Journal of Magnetics
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• v.21 no.1
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• pp.65-71
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• 2016

To increase the retaining force, a novel design for a concentric, bi-directional, electromagnetic valve actuator that contains double-layer permanent magnets is presented in this paper. To analyze the retaining-force change caused by the magnets, an equivalent magnetic circuit (EMC) model is established, while the EMC circuit of a double-layer permanent-magnet valve actuator (DLMVA) is also designed. Based on a 3D finite element method (FEM), the calculation model is built for the optimization of the key DLMVA parameters, and the valve-actuator optimization results are adopted for the improvement of the DLMVA design. A prototype actuator is manufactured, and the corresponding test results show that the actuator satisfies the requirements of a high retaining force under a volume limitation; furthermore, the design of the permanent magnets in the DLMVA allow for the attainment of both a high initial output force and a retaining force of more than 100 N.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.911-918
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• 2008

In this paper, we propose new cell structures using multi-hop Relay Station(RS) based on IEEE802.16j in Narrow-Beam Trisector Cell (NBTC) and Wide-Beam Trisector Cell (WBTC), which are two methods for cell sectorization using 3-sector directional antennas. Then, we analyze our proposed structures compared with the existing system which does not use any RS about the numbers of optimized Base Station (BS) and multi-hop relay, the extended BS coverage, and the deployment cost according to the traffic density using optimization model. According to the results, we know the reduction of total deployment cost of the proposed systems and that WBTC is suitable when the traffic density is high and NBTC is suitable when the traffic density is low in our proposed multi-hop based NBTC and WBTC structures.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.80-82
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• 2005

Distributed generation (IX;) plays an important role in the power system nowadays. Over-current relay, widely used in the DG protection, causes a wide outage section and long time delay. This paper proposes a DG protection technique to minimize the outage section. The proposed method uses three directional over-current relays with delay, which are connected to the point of common coupling. The method can minimize the outage section.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.450-452
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• 2005

Distributed generation (DG) plays an important role in the power system nowadays. Over-current relay, widely used in the DG protection, causes a wide outage section and long time delay. This paper proposes a DG protection technique to minimize the outage section. The proposed method uses three directional over-current relays with time delay, which are connected to the point of common coupling. The method can minimize the outage section.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.456-458
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• 2005

송전선로에서 발생하는 고장은 낙뢰나 수목접지로 인한 순간 고장이 대다수를 차지한다. 따라서 송전선로 보호 기능에 있어서 재폐로 기능은 계통의 안정성 향상과 공급 신뢰도의 제고를 위해서 중요한 역할을 담당한다. 본 논문에서는 154kV 송전선로 보호에 널리 사용되고 있는 디지털 방향비교 보호방식(Directional Comparison Blocking Scheme)에서 보호 구간 내부에 고장이 진전되어 발생했을 때, 재폐로 기능의 동작 특성에 대한 성능 검증 방안에 대해서 기술한다.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.535-536
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• 2006

In the embedded system, external device interface that operates serial protocol with lower speed than the general computers is used commonly. This paper describes I2C bus protocol that is a bi-directional serial bus with a two-pin interface. The I2C bus requires a minimum amount of hardware to relay status and reliability information concerning the processor subsystem to an external device.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.67-73
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• 1996

Subsynchronous resonance(SSR) causes a torsional shaft torque on the generator. Damages resulting from the uncontrolled SSR have resulted in the breakdown in the shaft and costs for replacement power. This paper is to determine the feasibility of controlling SSR by the fast modulation of series compensation capacitors. The presence of subsynchronous currents in the system was detected by a subsynchronous relay which was modeled by the transient analysis of control systems(TACS) in electromagnetic transients program (EMTP). The capacitor segments were switched by bi-directional thyristor switches. These were modeled into EMTP. The strategy to switch the capacitors were modeled as a closed loop system. The paper proves that effective control of SSR can be obtained only by the detuning of the system and the removal or blocking of subsynchronous energy from the system. (author). refs., figs., tabs.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.803-805
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• 1993

This paper describes the development of a digital multifunction controller for the protection, measurement and control of the high voltage customer switchboard. The magnitude of the fundamental component is estimated using a simple filter based on cross-correlation with a heptagonal wave. The characteristics of flexible relay functions such as adjustable pickup and time-dial settings, various time-magnitude curve and directional capability including measurement functions are presented. The controller implementation is carried out on two microprocessors for real time operation.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.434-436
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• 1995

This paper was to determine the feasibility of controlling subsynchronous resonance(SSR) by the fast modulation of series compensation capacitors. The presence of subsynchronous currents in the system was detected by a subsynchronous relay which was modeled by the transient analysis of control systems (TACS) in the electromagnetic transients program (EMTP). The capacitor segments were switched by bi-directional thyristor swtiches. The paper proved that effective control of SSR can be obtained only by the detuning of the system and the removal or blocking of subsynchronous energy from the system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.198-201
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• 2015

The prompt and accurate location determination of the nodes of the wireless indoor shipboard networks is crucial to forming the stable wireless shipboard sensor networks. To this end in this paper it can be achieved through the measurement of the bi-directional channel qualities among the nodes after the locations of the sensor nodes temporarily placed. For the 1st stage the piconet-type sensor networks are considered to measure the channel qualities between a specific node and the cluster node which is the master node. After finishing the 1st stage measurement the nodes needing the relay nodes are selected and the measurement action goes into the 2nd stage. In the 2nd stage the measurement between a candidate relay node and the node needing a relay node starts to begin. After the 2nd stage the relay nodes to connect to the cluster node are fixed and the information delivery paths between a node and the cluster head are established. In this paper the measurement results in the realistic environment are gathered and analysed to show that the measurement procedure can be applied in the wireless indoor shipboard networks.