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정전구간 최소화를 위한 방향과전류계전기 기반 분산전원 보호 방법
강용철(Kang, Yongcheol),이병은(Lee, Byungeun),김은숙(Kim, Eunsuk),황태근(Hwang, Taekeun),이지훈(Lee, Jihoon),차선희(Cha, Sunhee),박종민(Park, Jongmin),정태영(Jung, Taeyoung) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.06
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.
무효전력을 고려한 마이크로그리드의 단독운전 판단 알고리즘
강용철(Yongcheol Kang),장성일(Sungil Jang),차선희(Sunhee Cha),이병은(Byungeun Lee),김연희(Yeonhee Kim),이지훈(Jihoon Lee),김용균(Yongguen Kim) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
A microgrid is a new type of power system which is formed by the interconnection of small generator to distribution systems. Microgrids are able to supply electric power to their loads independently, which is called with islanding operation, even if they're separated from the power system. As a result, microgrids must be equipped with specific islanding detection schemes for the islanding operation of microgrids. This paper studies an islanding detection method considering reactive power. The proposed method is dealing with the reactive power of the cable which connects between a microgrid and a power system. To show the validity of the proposed method, many islanding operation cases are tested by varying the load conditions of microgrids.
히스테리시스 특성을 고려한 CCVT 2차 전압 보상 방법
강용철(Yongcheol Kang),정태영(Taiying Zheng),김연희(Yeonhee Kim),장성일(Sungil Jang),김용균(Yonggyun Kim) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
A coupling capacitor voltage transformer (CCVT) is used in extra high voltage and ultra high voltage transmission systems to obtain the standard low voltage signal for protection andmeasurement. To obtain the high accuracy at the power system frequency, a tuning reactor is connected between a capacitor and a voltage transformer (VT). Thus, no distortion of the secondary voltage is generated when no fault occurs. However, when a fault occurs, the secondary voltage of the CCVT has some errors due to the transient components resulting from the fault. This paper proposes an algorithm for compensating the secondary voltage of the CCVT in the time domain. With the values of the secondary voltage of the CCVT, the secondary and the primary currents are obtained; then the voltage across the capacitor and the tuning reactoris calculated and then added to the measured secondary voltage. The proposed algorithm includes the effect of the non-linear characteristic of the VT and the influence of the ferro-resonance suppression circuit. Test results indicate that the algorithm can successfully compensate the distorted secondary voltage of the CCVT irrespective of the fault distance, the fault inception angle and the fault impedance.
전압 불평형과 발전기 출력 변동을 이용한 분산전원의 단독운전 판단 기법
강용철(Yongcheol Kang),장성일(Sungil Jang),이지훈(Jihoon Lee),차선희(Sunhee Cha),김연희(Yeonhee Kim),이병은(Byungeun Lee),김용균(Yongguen Kim) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
Islanding operations of DG usually occur when power supply from the main utility is interrupted due to several reasons but the DG keeps supplying power into the distribution networks. These kinds of islanding conditions cause negative impacts on protection, operation, and management of distribution systems. Therefore, it is necessary to effectively detect the islanding conditions and swiftly disconnect DG from distribution network. This paper proposes the islanding detection algorithm for DG using the change of the voltage unbalance and the output power of DG. The proposed method effectively combines the conventional parameters for detecting the islanding conditions. The proposed methods were verified using the radial distribution network of IEEE 34 bus.
강용철(Yongcheol Kang),이병은(Byungeun Lee),이현웅(Hyunwoong Lee),김유다(Judah Kim),박준수(Junsu Park),이미선(Misun Lee),박지연(Jiyeong Park),이보은(Boeun Lee) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
A current differential relay has been used for transmission line protection. The relay may maloperate in the case of a failure of the secondary circuit of a current transformer (CT) because the differential current is produced. This paper presents an algorithm to detect a failure of a CT using the zero-sequence current. If the magnitude of the zero-sequence current is the same as the magnitude of the current of the other healthy phases, a failure of a CT is detected and then the blocking signal is activated. The proposed algorithm prohibit the maloperation of a differential relay in the case of a CT failure and thus increase the security of the relay.