• 한국산업융합학회 논문집
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• 제17권3호
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• pp.103-112
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• 2014

BY the Transformers and reactors, the input electrical energy is converted into magnetic energy. At the end through the magnetic energy was passed at the output parameter. Specially At the flyback transformer or a reactor airgap were designed to contain more magnetic energy. But that work is very difficult for the optimal design. It is that Contradictions are between the length of the Air-gap, Winding inductance, DC bias. As to e Several conflicting conditions in order to determine the optimum Air-gap has a lot of experience and trial & error is necessary. The approach proposed in this paper, the auxiliary winding on the core attached to part of primary core, that by applying a DC voltage has a dramatic effect like Core with designed Air-gap. This inventiveness and advantage is to regulate arbitrarily the Saturation Flux Quantity by the input signal to secondary winding. Accordingly obtained the biggest effect is that increasing limits of the saturation current destined by the material and shape of the conventional core. In other words, that can decreas the size of the transformer and reactor, While maintaining the current saturation capacity. This paper, prove its effect as using the local flux saturation in transformers and reactors for research by the computer program using the finite element method (FEM) simulation, followed by actual experiment to verify

• 대한전기학회논문지:전력기술부문A
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• 제53권9호
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• pp.500-506
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• 2004

This paper proposes a modified current differential relay for transformer protection unaffected by the remanent flux. 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. To cope with the remanent flux, before saturation, the relay calculates the core-loss current and uses it 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 actual 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. 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 discriminates magnetic inrush and over-excitation from an internal fault and is not affected by the level of remanent flux.

• 조명전기설비학회논문지
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• 제25권2호
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• pp.137-142
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• 2011

In this paper, the fault current limiting and the hysteresys characteristics of a superconducting fault current limiter (SFCL) using magnetic coupling of two coils on the iron core with an air-gap were analyzed. The introduction of the air-gap in the SFCL with magnetically coupled two coils can suppress the saturation of the iron-core and, on the other hand, make the limiting impedance of the SFCL decreased, which results from the increase of the exciting current. To analyze the effect of the aig-gap on the fault current limiting characteristics of the SFCL, the hysteresys curves of the iron core comprising the SFCL were derived from the short-circuit experiment and the variation in the voltage-current trace of the SFCL during the fault period was analyzed. Through the comparison with the current limiting characteristics of the SFCL without air-gap, the air-gap could be confirmed to contribute to the suppression of the iron core's saturation through the increase of the SFCL's burden from the short-circuit current.

• 한국초전도ㆍ저온공학회논문지
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• 제20권1호
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• pp.15-18
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• 2018

In this paper, the magnetizing characteristics of the current limiting reactor (CLR) using $high-T_C$ superconducting (HTSC) module were analyzed. Since the saturation of iron core comprising the CLR using HTSC module deteriorates its current limiting operation, the design of the CLR using HTSC module considering the magnetizing characteristics is needed. For the analysis on the magnetizing characteristics, the flux linkage and the magnetizing current of this CLR using HTSC module were derived from its electrical equivalent circuit. Through the analysis on the linkage flux versus the magnetizing current, obtained from the short-circuit tests, the suppressing effect of the iron core's saturation was discussed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.591-599
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• 2001

The paper identifies a severe form of core saturation instability in an DC/AC interaction system. It then seeks solutions to the problem by HVDC control means. This is achieved by a proper design of the Voltage Dependent Current Order Limiter (VDCOL), the Current Regulator and Timing Pulse generator. Supplementary control loops have also been introduced to result in a satisfactory performance as compared to that obtained one with the use of uncharacteristic harmonic filter on the AC side. Robustness of all the options has been demonstrated through recovery performance of the DC link in response to both I-phase and 3-phase 5 cycle faults on both rectifier and inverter commutating buses.

• Journal of Power Electronics
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• 제2권4호
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• pp.297-304
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• 2002

The paper identifies a severe form of core saturation instability in a DC/AC interaction system. It then seeks solutions to the problem by HVDC control means. This is achieved by a proper design of the Voltage Dependent Current Order Limiter (VDCOL), the Current Regulate. and Timing Pulse generator. Supplementary control loops have also been introduced to result in a satisfactory performance as compared to that obtained one with the use of uncharacteristic harmonic filter on the AC side. All the options have been demonstrated through recovery performance of the DC link in response to both 1-phase and 3-phase 5 cycle faults on both rectifier and inverter commutating buses.

• 한국전자통신학회논문지
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• 제10권7호
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• pp.781-786
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• 2015

본 논문은 과전류 경고회로의 신호를 나타내는 변류기를 설계하기 위해 관통형 변류기의 특성을 분석하고 손실을 고려한 최적 설계를 수행하였다. 관통형 변류기 코어의 크기는 2차측의 코일 턴수에 따라 결정된다. 우리는 코어에 코일을 감는 턴수에 따라 다르게 나타나는 전류 파형을 분석하였으며, 변류기 코어의 자속포화에 의한 비정현적인 파형을 개선하고자 2차측 코일 턴수와 부하저항과의 관계를 확인하였다. 또 코어의 외경은 유지하면서 내경 및 적층을 변화시켜 정밀도 개선 및 최적설계를 하였고, 이를 통하여 과전류 경고회로의 동작에 필요한 전류 값을 도출하였다.

• 대한전기학회논문지:전력기술부문A
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• 제55권3호
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• pp.95-101
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• 2006

This paper proposes a modified current differential relay for $Y-{\Delta}$ 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.9-13
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• 2004

This paper proposes a modified current differential relay for Y-$\Delta$ 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. The relay correctly discriminates magnetic inrush and over-excitation from an internal fault and is not affected by the level of remanent flux.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.262-265
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• 2003

During magnetic inrush or over-excitation saturation of the core in a transformer draws a large exciting current. This can cause mal-operation of a differential relay. This paper proposes a modified current differential relay for transformer protection. In order to cope with the remanent flux at the beginning. the start of saturation of the core is detected and the core flux at the instant is estimated by inserting the differential current into a magnetization curve. Then, this core flux value can be used to calculate the core flux. The proposed relay calculates the core-loss current from the induced voltage and the core-loss resistance; the relay calculates the magnetizing current from the core flux and the magnetization curve. Finally, the relay obtains the modified differential current by subtracting the core-loss current and the magnetizing current from the conventional differential current. The proposed technique not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the speed of the conventional relay.