• Proceedings of the KIEE Conference
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• summer
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• pp.363-365
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• 2004

This paper proposes a hardware implementation of intelligent electronic device for power transformer protection. And proposes an advanced main protection algorithm by voltage-current trend and flux-differential current slope characteristics. The secondary protection functions include UR, OCGR, OVR, and W etc. The main board of IED is based on the DSP chip TMS32C32 processor The IED was tested with relaying signals obtained for EMTP simulation package.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.415-423
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• 2018

We herein investigate the E1 pulse for evaluating the conducted performance of transmission lines connected to the electromagnetic pulse protection facilities against a conducted high-altitude electromagnetic pulse threat exposed to an external electromagnetic environment. The existing E1 pulse generator uses the Marx generator high-voltage step-up method; however, in this research, we used the Tesla transformer method to easily change the broadband output voltage(30 to 350 kV). We also analyzed the controller, power supply, high-voltage booster, and pulse-shaping device. The E1 pulse performance using the Tesla transformer was predicted through simulations and validated by measurements.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.467-469
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• 2000

This paper describes an application of discrete wavelet transform for power transformer protection. It is shown that the moving wavelet coefficients method based feature extraction for discrimination between actual internal faults and energizing state. The simulations of power transformer have been carried out using EMTP. The proposed method is more effectively and simpler to distinguish internal faults from inrush currents.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.2
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• pp.80-86
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• 2004

During magnetic inrush or over-excitation, saturation of the core in a transformer draws a large exciting current, which can cause mal-operation of a differential relay. This paper proposes a modified current differential relay for transformer protection. The relay calculates 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 and the magnetizing currents from the conventional differential current. Comparison study with the conventional differential relay with harmonic blocking is also shown. The proposed technique not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the speed of the conventional relay.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.6
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• pp.221-226
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• 2006

The current flowing though a power line is measured by a current transformer (CT). Since a CT is a kind of transformer, saturation of magnetic flux in the core may occur when a large primary current flows. This saturation makes the secondary current of a CT distorted and causes problems in the protection point of view. Because of the current distortion, a protection relay cannot collect the correct information showing how the primary power system changed. Consequently, the current distortion may cause the mal-operation or operation time delay of protective relay. In this paper, an algorithm based on AR model and LSQ is proposed to compensate the saturated CT secondary currents. Various test results indicate that the proposed algorithm can accurately compensate a severely distorted secondary current and is not affected by remanence.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2281-2283
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• 1998

In this paper, we propose a digital differential protection of power transformer using intelligent schemes. Intelligent schemes is based on fuzzy logic and neural networks. To enhance the distinction between fault and inrush of conventional approaches, relaying technique by fuzzy logic and neural networks are used. We used transformer inrush currents, external and internal fault signals, which are obtained from EMTP simulation.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.1
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• pp.37-45
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• 1993

A parametric transformer, as static power converter operating on the principle of parametric excitation, is analysed. For the purpose of quantitative analysis of device, the mathematical model of the device is derived. On the basis of this model, the performances of the parametric transformer, such as over and under voltage protection, overload protection, bilateral filtering and frequency multiplication, are obtained quantitatively and analysed qualitatively.

• KIEE International Transactions on Power Engineering
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• v.5A no.1
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• pp.1-8
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• 2005

During magnetic inrush or over-excitation, saturation of the core in a transformer draws a significant exciting current, which can cause malfunction of a current-differential relay. This paper proposes a modified-current-differential relay for transformer protection. The relay calculates the core-loss current from the induced voltage and the core-loss resistance as well as the magnetizing current from the core flux and the magnetization curve. Finally, the relay obtains the modified differential current by subtracting the core-loss and the magnetizing currents from the conventional differential current. A comparative study of the conventional differential relay with harmonic blocking is presented. The proposed relay not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the relay speed.

• KIEE International Transactions on Power Engineering
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• v.3A no.2
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• pp.70-78
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• 2003

This paper describes a transformer protection relay based on induced voltages. The ratio of the induced voltages of the primary and secondary windings is equal to the turns ratio during normal operating conditions such as magnetic inrush, overexcitation, and steady state, but it differs from the turns ratio in the case of internal faults. For a single-phase and a three-phase Y-Y transformer, the induced voltages are estimated and the ratios are compared with the turns ratio. For three-phase Y-Δ transformers, the differences between the induced voltages are estimated to use the line currents because delta-winding currents are practically unavailable. The proposed relay is tested under various conditions such as magnetic inrush, internal winding faults, overexcitation, and different core characteristics. The results evidently indicate that the relay successfully discriminates internal faults from magnetic inrush and overexcitation. This paper concludes by implementing the relay into a TMS320C6701 digital signal processor and reports satisfactory results. The relay requires no hysteresis data and can reduce the operating time of a relay.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.208-209
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• 2006

Voltage Transformer is used to transform high voltage into low voltage to input signal of protection relay. Most of the Voltage Transformers use the iron core which maximizes the flux linkage. The ratio of the Voltage Transformer depends on the transformer turns ratio. The current which flows in the Voltage Transformer has non-linear characteristic caused by hysteresis of the iron core, it causes a voltage loss in the winding impedances which makes measurement errors. This paper describes an error compensation method considering hysteresis characteristic. The proposed compensation method improves error by calculating the primary current from the exciting current of the hysteresis loop in the Voltage Transformer, compensating the voltage loss.