• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.208-210
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• 1998

A high speed digital distance relaying algorithm based on a modified least square error method is proposed. To obtain stable phasor values very Quickly, first, a lowpass filter which has very short transient period and no overshoot is used. Secondly, the conventional least square error method is modified to the one having the data window of 3 samples by applying a FIR filter which removes the DC-offset component in current relaying signals.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.121-124
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• 1990

Distance relaying is one of the most commonly used protection schemes in the high voltage transmission systems. In this scheme, coordination between the primary and backup relays is very critical for the power system security. This paper reports an rule-based methodology for checking and correction of miscoordination problems in the distance relaying. Diagnosis rules achieving an accurate but simple checking have been developed through the geometric analysis of the impedance characteristics of the distance relays. Heuristic rules having the pratical power for miscoordination correction are suggested. The proposed method has proved very effective through the several case studies on the actual systems.

• Journal of Communications and Networks
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• 제17권5호
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• pp.463-472
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• 2015

This paper considers a limited feedback system for two-way wireless relaying channels with physical network coding (PNC). For full feedback systems, the optimal structure with the PNC has already been studied where a modulo operation is employed. In this case, phase and power of two end node channels are adjusted to maximize the minimum distance. Based on this result, we design new quantization methods for the phase and the power in the limited feedback system. By investigating the minimum distance of the received constellation, we present a code-book design to maximize the worst minimum distance. Especially, for quantization of the power for 16-QAM, a new power quantization scheme is proposed to maximize the performance. Also, utilizing the characteristics of the minimum distance observed in our codebook design, we present a power allocation method which does not require any feedback information. Simulation results confirm that our proposed scheme outperforms conventional systems with reduced complexity.

• 한국지능시스템학회논문지
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• 제8권2호
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• pp.9-20
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• 1998

본 논문에서는 패턴인식 형태로 구성된 거리계전시스템에 신경회로망을 적용한 새로운 형태의거리계전기법이 제시되었다. 제안된 거리계전기법은 패턴인식 단계인 두개의 블록으로 구성되었다. 첫 단계에서는 과도신호의 특징 파라미터인 기본파성분을 효율적으로 추출하기 위해 신경회로망을 이용한 필터링 방법이 적용되었으며, 두번째 단계에서는 첫단계에서 추출된 기본파성분을 입력으로 고장형태를 신속하고 정확하게 판별 분류 될 수 있도록 신경회로망을 이용한 고장패턴 추정기가 개발적용되었으며, 이울러 고장판별에 따라 고장점을 효율적으로 추정될 수 있도록 하였다. 적용 시스템의 각 단계는 함수 근사화, 보간성능 및 패턴분류 등의 능력이 뛰어난 다층 퍼셉트론의 역전파 학습 알고리즘이 적용되었다. 제신된 기법의 성능을 입증하기 위하여 EMTP 시뮬레이션을 하여 얻은 다양한 과도 고장파형의 계전시호를 활용하여 시험하였으며, 그결과 제시된 기법은 학습되지 않은 임의의 패턴에 대하여 적응성을 가지고 효율적으로 고장점이 추정될 수 있었으며, 고장발생후 3샘플 이내에서 고장형태가 신속하고도 정확하게 판별되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.2195_2196
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• 2009

DC-offset is a very important subject in power systems protection, since DC-offset causes mal-operation of the distance relay. This paper deals with the influence of a FIR filter used for removing the DC-offset upon the convergence characteristics of distance relaying algorithm based on Fourier Transform.

• Journal of Communications and Networks
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• 제13권4호
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• pp.393-399
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• 2011

We evaluate the link-level performance of cooperative multi-hop relaying networks with an maximum distance separable (MDS) code. The effect of the code on the link-level performance at the destination is investigated in terms of the outage probability and the spectral efficiency. Assuming a simple topology, we construct an absorbing Markov chain. Numerical results indicate that significant improvement can be achieved by incorporating an MDS code. MDS codes successfully facilitate recovery of the message block at a relaying node due to powerful error-correcting capability, so that it can reduce the outage probability. Furthermore, we evaluate the average number of hops where the message block can be delivered.

• 전기학회논문지
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• 제59권8호
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• pp.1360-1365
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• 2010

In this paper, we propose a distance relaying algorithm using a Discrete Fourier Transform (DFT)-based modified phasor estimation method to eliminate the adverse influence of exponentially decaying DC offsets. Most distance relays are based on estimating phasors of the voltage and current signals. A DFT is generally used to calculate the phasor of the fundamental frequency component in digital protective relays. However, the output of the DFT contains an error due to exponentially decaying DC offsets. For this reason, distance relays have a tendency to over-reach or under-reach in the presence of DC offset components in a fault current. Therefore, the decaying DC components should be taken into consideration when calculating the phasor of the fundamental frequency component of a relaying signal. The error due to DC offsets in a DFT is calculated and eliminated using the outputs of an even-sample-set DFT and an odd-sample-set DFT, so that the phasor of the fundamental component can be accurately estimated. The performance of the proposed algorithm is evaluated for a-phase to ground faults on a 345 kV, 50 km, simple overhead transmission line. The Electromagnetic Transient Program (EMTP) is used to generate fault signals. The evaluation results indicate that adopting the proposed algorithm in distance relays can effectively suppress the adverse influence of DC offsets.

• 대한전기학회논문지
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• 제41권3호
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• pp.227-236
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• 1992

In this paper, a simulation program of relaying system including the CT and CPD ( capacitive potential device ) is developed to study the effect of its operation under various system conditions. To deal with the dynamic characteristics of relaying system, state space technique is applied, and then the state equations of CT, CPD and mho distance relay are constructed. Also the dynamic response characteristics of overall relaying system is verified by digital simulation. Since the proposed model is capable of taking arbitrary input waveforms from EMTP in analyzing its dynamic responses, the effects of CT-saturation and CPD-subsidence transient characteristics on the operating points of who distance relay can be accurately prodicted. It gives more effective results, compared with the model without considering those characteristics by checking the exprimental data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.509-512
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• 1995

The relaying algorithm to calculate the fault distance from only transient signal at faults in T/L is presented. In this paper. At faults the oscillation frequency components exist in both voltage and current and these components minimize the input impedance shown in fault point. The equivalent source impedance shown in relaying point is needed to calculate the fault distance using these components. To source impedance, the reflection coefficient between forward wave and backward and the Prony's analysis is also employed to extract the oscillation frequency component from transient signals. The case study show that the new distance relaying algorithm satisfies the high operation speed and high accuracy even if the algorithm uses only transient signals.

• 융합보안논문지
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• 제11권5호
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• pp.13-19
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• 2011

모바일 애드 혹 네트워크를 형성하는 노드들은 불규칙한 이동성을 갖기 때문에 소스 노드와 목적지 노드 간의 초기 경로 설정 시 임의의 시간동안 경로 유지가 가능한 최적의 중계 노드들을 선택하는 것이 중요하다. 이의 분석을 위해, 본 논문에서는 중계 노드들 간의 초기 거리 및 이동 속도를 고려한 링크 유지 확률을 유도하고 임의의 시간 동안 두 중 계노드 간 링크 유지가 가능한 최적의 거리를 제시하며, 이를 기반으로 임의의 두 노드 간에 설정되는 경로의 신뢰성을 분석한다.