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코어의 히스테리시스 특성을 고려한 CCVT 2차 전압 보상 알고리즘
강용철(Yong-Cheol Kang),정태영(TaiYing Zheng),강해권(Hae-Gweon Kang),장성일(Sung-Il Jang),김용균(Yong-Gyun Kim) 대한전기학회 2009 전기학회논문지 Vol.58 No.8
This paper proposes a compensating algorithm for the secondary voltage of a coupling capacitor voltage transformer (CCVT) in the time domain by considering the hysteresis characteristics of the core. The proposed algorithm estimates the three error terms i.e. the voltage across the secondary winding parameters, the voltage across the primary winding parameters, and the voltage across the capacitor and the tuning reactor. These three terms are added to the measured secondary voltage to obtain the correct voltage. The algorithm reduces the errors of the CCVT significantly both in the steady state and during a fault. The performance of the algorithm is verified under the various fault conditions by varying the fault distance, the fault inception angle, and the fault impedance with the EMTP generated data. Test results clearly indicate that the algorithm can increase the accuracy of a CCVT significantly under the fault conditions as well as in the steady state. The algorithm helps improve the performance of a protection relay or a metering device.
姜龍澈(Yong-Cheol Kang),鄭太英(Taiying Zheng),李知勳(Ji-hoon Lee),張成一(Sung-Il Jang),金容均(Yong-Gyun Kim) 대한전기학회 2008 전기학회논문지 Vol.57 No.6
A coupling capacitor voltage transformer (CCVT) is used in an extra or ultra high voltage system to obtain the standard low voltage signal for protection. To avoid the phase angle error between the primary and secondary voltages, a tuning reactor is connected between a capacitor and a voltage transformer. The inductance of the reactor is designed based on the power system frequency. If a fault occurs on the power system, the secondary voltage of the CCVT contains some errors due to a de offset component and harmonic components resulting from the fault. The errors become severe in the case of a close-in fault. This paper proposes an algorithm for compensating the secondary voltage of a CCVT in the time-domain. From the measured secondary voltage of the CCVT, the secondary and primary currents are obtained; then the voltage across the capacitor and the inductor is calculated and then added to the measured secondary voltage to obtain the correct primary voltage. Test results indicate that the proposed algorithm can compensate the distorted secondary voltage of the CCVT irrespective of the fault distance, the fault inception angle, and the burden of the CCVT.
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.
히스테리시스 특성을 고려한 전압 변성기 오차 보상 알고리즘
강용철(Yong-Cheol Kang),정태영(Taiying Zheng),박종민(Jong-Min Park),장성일(Sung-Il Jang),김용균(Yong-Guen Kim) 대한전기학회 2007 대한전기학회 학술대회 논문집 Vol.2007 No.11
A voltage transformer (VT) is used to transform a high voltage into a low voltage as an input for a metering device or a protection relay. VTs use an iron core which maximizes the flux linkage. The primary current of the VT has non-fundamental components caused by the hysteresis characteristics of the iron core. It causes a voltage drop in the winding impedances resulting in the error of the VT. This paper describes a compensation algorithm for the VT. The proposed algorithm can compensate the secondary voltage of VT by calculating the primary current from the exciting current of the hysteresis loop in the voltage transformer. In this paper, the exciting branch was divided into a non-linear core loss resistor and a non-linear magnetizing inductor. The performance of the proposed algorithm was validated under various conditions using EMTP generated data. Test results show that the proposed compensation algorithm can improve the accuracy of the VT significantly.
히스테리시스 특성을 고려한 측정용 변류기 2차 전류 보상 알고리즘
姜龍澈(Yong-Cheol Kang),蘇淳鴻(Soon-Hong So),鄭太英(Taiying Zheng),張成一(Sung-Il Jang),金容均(Yong-Gyun Kim) 대한전기학회 2007 전기학회논문지 Vol.56 No.10
This paper proposes a compensating algorithm for the secondary current of the measurement current transformer (CT) that removes the effects of the hysteresis characteristics of the iron-core. The exciting current resulting from the hysteresis characteristics of the core causes an error between the primary current and the secondary current of the measurement CT. The exciting current can be decomposed into the magnetizing current and the core loss current, The core Joss current is obtained from the measured secondary current and the core loss resistance. The core flux linkage is calculated by integrating the measured secondary current, and then inserted into the flux-magnetizing current curve to obtain the magnetizing current. The exciting current at every sampling interval is obtained by summing the core-loss and magnetizing currents and then added to the measured current to obtain the correct current. The performance of the proposed algorithm is validated under various conditions using EMTP generated data. The results indicate that the proposed algorithm can improve the accuracy of the measurement CT significantly, and thus reduce the size and the cost of the measurement CT.
姜龍澈(Yong-Cheol Kang),朴志蓮(Ji-Youn Park),鄭太英(Taiying Zheng),張成一(Sung-Il Jang),金容均(Yong-Gyun Kim) 대한전기학회 2008 전기학회논문지 Vol.57 No.2
An air-gapped current transformer (CT) has been used to reduce a remanent flux in the core, particularly in the case of auto-reclosure. However, it causes larger transient, ratio and phase errors than the iron-cored CT because of the small magnetizing inductance. This paper proposes a compensation algorithm for the secondary current of the air-gapped CT during the fault conditions including auto-reclosure as well as in the steady-state. The core flux is calculated from the measured secondary current of the CT and inserted into the hysteresis loop to estimate the exciting current. Finally, the correct current is estimated by adding the measured secondary current to the estimated exciting current. Various test results clearly indicate that the proposed compensating algorithm can improve the accuracy of the air-gapped CT significantly and reduce the required core cross-section of the air-gapped CT significantly.
姜龍澈(Yong-Cheol Kang),金烟熙(Yean-Hee Kim),鄭太英(Taiying Zheng),張成一(Sung-Il Jang),金容均(Yong-Gyun Kim) 대한전기학회 2008 전기학회논문지 Vol.57 No.6
Coupling capacitor voltage transformers (CCVTs) have been used in extra or ultra high voltage systems to obtain the standard low voltage signal for protection and measurement. For fast suppression of the phenomenon of ferroresonance, three winding CCVTs are used instead of two winding CCVTs. A tuning reactor is connected between a capacitor voltage divider and a voltage transformer to reduce the phase angle difference between the primary and secondary voltages in the steady state. Slight distortion of the secondary voltage is generated when no fault occurs. However, when a fault occurs, the secondary voltage of the CCVT has significant errors due to the transient components such as dc offset component and/or high frequency components resulting from the fault. This paper proposes an algorithm for compensating the secondary voltage of a three winding CCVT in the time domain. With the values of the measured secondary voltage of the three winding CCVT, the secondary, tertiary and primary currents and voltages are estimated; then the voltages across the capacitor and the tuning reactor are calculated and then added to the measured voltage. Test results indicate that the algorithm can successfully compensate the distorted secondary voltage of the three winding CCVT irrespective of the fault distance, the fault impedance and the fault inception angle as well as in the steady state.