• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.217-219
• /
• 2004

The installation of small sized dispersed generation(DG) units operating in parallel with the utility supply presents several technical problems for the protection and control of the system. One of the critical concerns is the occurrence of islanding. Hence, this paper propose the Digital Universal Relay(DUR) including anti-islanding function as DG interconnection interface. The existent islanding detection algorithms are examined. And the most effective and reliable method of those is modified for DUR application. The modified algorithm is evaluated through the modeling of the test system by PSCAD/EMTDC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.2
• /
• pp.131-137
• /
• 2005

Protective relays provide important features to electrical power systems for protecting against faults and consequent short circuits. This research presents a novel VLSI design of the digital protective relay, which overcomes today's uP/DSP-based relays. This design features good cancellation of DC/k-th harmonic components, noticeable not performance and flexible Protection behavior in the minimized core area The proposed design was successfully implemented by a FPGA(Field Programmable Gate Array) device and can concurrently process over 16KSPS at less $0.03[\%]$ error rate.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.49 no.12
• /
• 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.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.53 no.3
• /
• pp.175-181
• /
• 2004

The protection against transient instability and consequent out-of-step condition is a major concern for the utility industry. Unstable system may cause serious damage to system elements such as generators and transmission lines. Therefore, out-of-step detection is essential to operate a system safely. The detection of out-of-step is generally based upon the rate of movement of the apparent impedance. However such relay monitors only the apparent impedance which may not be sufficient to correctly detect all forms of out-of-step and cannot cope with out-of-step for a more complex type of instability such as very fast power swing. This paper presents the out-of-step detection algorithm using voltage frequency deviation. The digital filters based on discrete Fourier transforms (DFT) to calculate the frequency of a sinusoid voltage are used, and the generator angle is estimated using the deviation of the calculated frequency component of the voltage. The proposed out-of-step algorithm is based on the assessment of a transient stability using equal area criterion. The proposed out-of-step algorithm is verified and tested by using EMTP MODELS.

• Proceedings of the KIEE Conference
• /
• 2003.07a
• /
• pp.345-347
• /
• 2003

본 논문에서는 디지털 보호 계전기에 쓰이는 필터 중에서 최소 자승 알고리즘을 이용한 고성능 FIR 필터를 설계하였다. 기존의 DFT필터와 MATLAB 시뮬레이션을 이용하여 비교하였으며 FIR 필터의 VHDL모델 및 합성에 중점을 두었다. FIR 필터는 기본적으로 유한개의 임펄스 응답이 이루어지기 때문에 기타 다른 필터에 비하여 안정도가 높으며 선형적인 위상을 가지기 때문에 차단 주파수 대역의 왜곡현상을 없앨 수 있는 장점을 가지고 있다. 여러 가지 알고리즘으로 구현한 FIR 필터를 시뮬레이션 한 결과 최소 자승 알고리즘이 가장 우수한 결과를 나타내었다. 기본적으로 디지털 보호 계전기에서 디지털 필터의 기능은 사고 전압, 전류로부터 60Hz의 기본파 추출 CT, PT 왜곡 및 DC offset을 제거하는데 있다. 본 논문에서는 이러한 기능을 가지면서 샘플링 주파수와 차수를 같게 하여 FIR 필터와 DFT 필터의 주파수 응답과 연 산 속도를 비교 하였다. 본 논문에서 설계된 최소 자승 알고리즘을 이용한 FIR 필터는 같은 조건의 DFT필터에 비해 1고조파와 2고조파의 차이가 10db 이상 더 우수 하였으며 연산 속도 또한 2배 이상 좋은 결과를 보였다.

• KEPCO Journal on Electric Power and Energy
• /
• v.6 no.3
• /
• pp.253-257
• /
• 2020

The local information processing devices are devices that process information by converting voltage, current, and digital electric signals from legacy-type power facility into IEC 61850 based data. It acquires and processes the operation information of legacy-type power facility, performs control of power facility, and interlock function using internal logic. In particular, the time to convert data to process input and output information for a device is important because a number of protection relay input and output signals are handled by only one device. This paper introduces test methods and cases for measuring IEC 61850 communication function and input/output data conversion time of local information processing device.