• KIEE International Transactions on Power Engineering
• /
• 제4A권4호
• /
• pp.236-242
• /
• 2004

Previous research results indicated that the designed current reduction device could effectively reduce the sheath circulating current and that its RDP protection device could shield it against both fault and lightning strokes. In this paper, cable impedance is analyzed using wavelet analysis and distance relay algorithm following the installation of these devices so that the operation of distance relay can be estimated. The test results confirm that in these devices, the fault inception angle and SVL bonding types have no impact on the change of cable impedance. In other words, the conventional distance relay can be used without a new relay setting. Thus we can finally assert that the designed current reduction device and its protection device are effective and can be safely installed on the cable transmission system without disturbance.

• 인터넷정보학회논문지
• /
• 제3권1호
• /
• pp.1-10
• /
• 2002

원격 영상전송 장치는 안전상의 문제가 있거나 사람이 갈 수 없는 곳을 관찰하기 위해 로봇 기술과 영상전송 기술을 결합한 것이다. 최근 원격 제어를 위해 웹서버와 로봇간 유선 및 RF를 이용한 제어 장치들이 개발되고 있지만, 작동 거리 및 인터넷 라인을 설치해야 하는 제한점이 있으며, 무선 방식의 통신장비를 이용할 경우 무선 라우터의 가격이 고가라는 문제가 있다. 본 연구에서는 이러한 문제점을 해결하기 위해 셀룰러 폰 통신망을 이용하여 영상전송 및 영상전송 장치를 원격으로 제어할 수 있는 시스템을 개발하였으며, 개발된 시스템은 기존의 무선통신(RF)을 이용한 영상 전송시의 단점인 거리 제한 문제와 인터넷을 이용한 영상전송시의 문제를 해결할 수 있었고, 현재의 통신망을 비롯한 제한된 조건 하에서 최적의 영상 및 음성을 전송할 수 있었다.

• 한국항행학회논문지
• /
• 제20권3호
• /
• pp.246-251
• /
• 2016

본 논문에서는 자기공진방식 무선전력전송 표준인 A4WP (alliance for wireless power) 주파수 6.78 MHz에서, 1 m 거리 무선전력전송 안테나를 최적화하고 이에 따른 시뮬레이션 및 측정 결과를 비교하였다. 전력전송 거리는 시스템 형태, 안테나의 크기, 공진기내 코일과 코일사이 간격인 피치(pitch) 등 다양한 요인에 따라 영향을 받으며, 전자계 시뮬레이션을 통해 이를 확인하였다. 시뮬레이션을 통해 고정된 거리에 대하여 최적화된 무선전력전송 안테나를 설계하였으며, 거리에 따른 전송손실인 ${\mid}S_{21}{\mid}$ 값을 계산하였다. 설계된 안테나를 제작하여 측정치를 시뮬레이션 값과 비교한 결과, 최대 1.3 m 거리에서 시뮬레이션은 전송손실 1.6dB 및 효율 69 %, 측정결과는 전송손실 1.5dB 및 효율 70 %를 나타내었다.

• 대한전기학회논문지:전력기술부문A
• /
• 제49권12호
• /
• pp.595-601
• /
• 2000

This paper describes the improvement method of distance relaying algorithm for the underground transmission cables. Distance relaying algorithms have been mainly developing to protect the overhead transmission lines than the underground cables. If the cable systems are directly protected using distance relaying algorithm developed for overhead line without any improvement, there will be really occurred many misoperation in cable systems, because the cable systems consist of the conductor, the sheath, several grounding method, cable cover protection units(CCPUs), and grounding wire. Accordingly, the complicated phenomena are occurred, if there is a fault in cable systems. Therefore, to develope a correct distance relaying algorithm, such cable characteristics should be taken into account. This paper presents the process to improve distance relaying algorithm which is now used. REal cable system was selected to establish modeling in EMTP and ATP Draw. It was discovered through the detailed simulation during the fault that the large error existed between impedance measured at the relay point and real impedance is due to the resistance of grounding wire in each grounding method. And also compensation factor obtained by the simulation is proposed in this paper. It is proved that the factor proposed can fairly improve the accuracy of impedance at the relay point. It is evaluated that the protective ability will be really much improved, if the algorithm proposed in this paper is applied for cable systems of utility.

• 센서학회지
• /
• 제23권1호
• /
• pp.46-50
• /
• 2014

In this paper, we report a novel algorithm based on phase displacement, which supplements conventional TOF methods for distance measurement using an ultrasonic wave. The proposed algorithm roughly measures the distance between the transmission part and the receiving part by using the initial TOF. Thereafter, the precise distance is determined by measuring the phase displacement value between the synchronizing transmission signal and the signal obtained at the receiving end. A distance measurement experiment using a micrometer was performed to verify the accuracy of the ultrasonic wave sensor system. We found that the mean errors from the one adopting the distance measurement algorithm based on phase displacement varied from a minimum of 0.03 mm to a maximum of 0.09 mm. In addition, the standard deviation varied from a minimum of 0.04 mm to a maximum of 0.07 mm, thus giving a precision of ${\pm}0.1$ mm.

• 조명전기설비학회논문지
• /
• 제26권2호
• /
• pp.51-60
• /
• 2012

An improved method for detecting fault distance in overhead transmission lines is described in this paper. Based on single-ended measurement, propagation theory of traveling waves together with the wavelet transform technique is used. In estimating fault location, a simple, but fundamental method using the time difference between the two consecutive peaks of transient signals is considered; however, a new method to enhance measurement sensitivity and its accuracy is sought. The algorithm is developed based on the lattice diagram for traveling waves. Representing both the ground mode and alpha mode of traveling waves, in a lattice diagram, several relationships to enhance recognition rate or estimation accuracy for fault location can be found. For various cases with fault types, fault locations, and fault inception angles, fault resistances are examined using the proposed algorithm on a typical transmission line configuration. As a result, it is shown that the proposed system can be used effectively to detect fault distance.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 하계학술대회 논문집 A
• /
• pp.440-442
• /
• 2000

This paper describes the digital distance algorithm in case of combined transmission line connected with overhead line and underground cable. Actually as fault is occurred in cable, it results in the complicated phenomena due to the several kind of grounding method in the sheath of cable. Accordingly the impedance. Therefore the correct impedance calculation algorithm is requested in combined transmission line to avoid the wrong trip of relay. This paper presents the development result of impedance calculation algorithm In such transmission line.

• 한국안전학회지
• /
• 제20권1호
• /
• pp.30-35
• /
• 2005

This study proposes construction of through transmission for weld defects detection of rail weld zone from ultrasonic signals. For these purposes, the ultrasonic signals for defects(porosity and crack) of weld zone in rails are acquired in the type of time series data and echo strength. 6 lines in the distance amplitude characteristics curve(DACC) indicated damage evaluation standard of weld zone in rails. The acquired ultrasonic signals agree flirty well with the mesured results of reference block and sensitivity block(defect location beam propagation distance, echo strength, etc). The proposed construction of through transmission in this study can be used for weld defects detection of rail weld zone.

• 대한전기학회논문지:전력기술부문A
• /
• 제54권12호
• /
• pp.573-579
• /
• 2005

Dynamic analysis of a transmission line which is compensated by a FACTS device such as STATCOM, SSSC and UPFC is carried out in this paper and the impacts on conventional line protection methods such as the DCPM (Differential Current Protection Method) and the DPM (Distance Protection Method) are reviewed. A refined DCRM is proposed to detect faults properly regardless of the FACTS operation. The proposed method is applied to a FACTS-compensated line with a variety of faults and is verified by simulation results. An adaptive DPM on a FACTS-compensated line was proposed previously in the literature. In order to emphasize the necessity of the modified DPM, the conventional DPM is applied to a FACTS-compensated system. Significant factors such as fault types, fault locations, and fault resistances as well as FACTS device types are considered for relaying setting.

• 대한전기학회논문지:전력기술부문A
• /
• 제53권8호
• /
• pp.432-437
• /
• 2004

Since the characteristic frequency is decreased in proportion to the fault distance, the characteristic frequency component may be insufficiently eliminated by a low-pass filter on a long transmission line. In order to set a standard for the cut-off frequency of the low-pass filter, this paper proposes a method for obtaining the characteristic frequencies due to line faults. The application results of the proposed method are presented for line to ground (LG) faults and line to line (LL) faults on a 345 kV 200 km overhead transmission line. The EMTP is used to generate fault signals under different fault locations and fault inception angles. By comparison between the characteristic frequencies obtained from the proposed method and the EMTP simulation, it is shown that the proposed method accurately obtains the characteristic frequency.