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CT와 CCVT의 오차를 고려한 거리 계전기의 응동 분석
강용철(Yong-Cheol Kang),정태영(Tai-Ying Zheng),최재선(Jae-Sun Choi),강해권(Hae-Gweon Kang),김광무(Kwang-Moo Kim),장성일(Sung-Il Jang),김용균(Yong-Gyun Kim) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.11
A distance relay has been widely used for transmission line protection. The distance relay detects a fault based on the calculated impedance i.e. the ratio of the voltage to the current measured from a current transformer (CT) and a coupling capacitor voltage transformer (CCVT), respectively. When a fault occurs and a C saturates due to the magnitude of fault current, dc component, primary time constant, and the remanent flux of the iron core, the secondary current of a CT is distorted. On the other hand, non-fundamental components generated during a fault can increase the error of a CCVT, particularly when a fault distance is short. The distortion of the current and voltage can cause mal-operation or the operating time delay of a distance relay. This paper describes the response of a distance relay considering the errors of a CT and a CCVT. The results indicate that the severe distortion of a CT and a CCVT have noticeable effect to a distance relay.
풍력단지의 Fault Ride-Through 기능을 위한 연계선 보호용 거리계전기의 성능향상 기법
강용철(Yong-Cheol Kang),강해권(Hae-Gweon Kang),정태영(Tai-Ying Zheng),이병은(Byung-Eun Lee),장성일(Sung-Il Jang),김용균(Yong-Gyun Kim) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
A large wind farm should satisfy the requirements for a grid and accomplish the optimization of the wind farm system. In that point of view, the wind farm intertie protection system, which must consider the Fault Ride-Through (FRT) requirement for more reliable protection, should be improved. This paper proposes a modified distance relay suitable for protection of a wind farm intertie considering a FRT requirement. The frequency change is used to discriminate the intertie fault from a outside zone fault. The performance of the proposed algorithm is verified using a PSCAD/EMTDC simulator.
강용철(Yong-Cheol Kang),이혜원(Hye-Won Lee),이병은(Byung-Eun Lee),강해권(Hae-Gweon Kang),배시화(Si-Hwa Bae) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.11
As the capacity of a wind farm grows larger and larger. it should be operated to minimise its effect to the grid. This paper presents analysis of response of a wind farm for a grid fault. For a fault, each turbine might generate different frequency components in the internal voltage. The internal voltages with different frequency components results in the currents with different frequencies. These might results in "beats" in the voltage and current signals of a wind farm. This phenomenon can cause some problems for a wind farm to do the fault ride-through requirement In addition, it may cause difficulties in protection relays of a wind farm. This paper analyze the response of a wind farm for various fault conditions using a PSCAD/EMTDC simulator.
Fault ride-through 요구를 고려한 풍력발전단지 연계선 보호 거리계전 알고리즘
강용철(Yong-Cheol Kang),강해권(Hae-Gweon Kang),정태영(Tai-Ying Zheng),김연희(Yeon-Hee Kim),이영귀(Young-Gui Lee) 대한전기학회 2010 전기학회논문지 Vol.59 No.6
A large modern wind farm should satisfy the requirements for a grid and accomplish the optimization of the wind farm system. The wind farm intertie protection system should consider a Fault Ride-Through (FRT) requirement for more reliable protection. The wind farm should keep connected to the grid in the case of a grid fault whilst it should be isolated for an intertie fault. This paper proposes a distance relaying algorithm suitable for wind farm intertie protection considering the FRT requirement. The proposed algorithm estimates the impedance based on a differential equation method because the frequency of the voltage and current deviates the nominal frequency. The algorithm extends the reach of Zone 1 up to 100 % of the length of the intertie to implement the FRT requirement. To discriminate an intertie fault from a grid fault, the algorithm uses a voltage blocking scheme because the magnitude of the voltage at the relaying point for an intertie fault becomes less than that for a grid fault. The performance of the algorithm is verified using a PSCAD/EMTDC simulator under various fault conditions. The algorithm can discriminate successfully the intertie fault from grid fault and thus helps to implement the FRT requirement of a wind farm.
姜龍澈(Yong-Cheol Kang),金恩淑(En-Shu Jin) 대한전기학회 2006 전기학회논문지A Vol.55 No.3
This paper proposes a modified current differential relay for Y-ㅿ, transformer protection. The relay uses the same restraining current as a conventional relay, but the differential current is modified to compensate for the effects of the exciting current. A method to estimate the circulating component of the delta winding current is proposed. To cope with the remanent flux, before saturation, the core-loss current is calculated and used to modify the measured differential current. When the core then enters saturation, the initial value of the flux is obtained by inserting the modified differential current at the start of saturation into the magnetization cure. Thereafter, the core flux is then derived and used in conjunction with the magnetization curve to calculate the magnetizing current. A modified differential current is then derived that compensates for the core-loss and magnetizing currents. The performance of the proposed differential relay was compared against a conventional differential relay. Test results indicate that the modified relay remained stable during severe magnetic inrush and over-excitation, because the exciting current was successfully compensated. This paper concludes by implementing the relay on a hardware platform based on a digital signal processor. The relay does not require additional restraining signal and thus cause time delay of the relay.