• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.4
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• pp.261-268
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• 2020

Transformer saturation in full bridge (FB) isolated DC-DC converters is caused by uneven switching speeds and voltage drops in semiconductor devices and mismatched gate signals. In order to prevent transformer saturation, most popular and widely used approach is to insert a capacitor in series with the transformer windings. This study conducts extensive analyses on transformer saturation and the effect of DC blocking capacitors when they are placed in the primary or secondary windings of a transformer. The effect of the DC blocking capacitors is verified in voltage-fed and current-fed FB converters.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.236-243
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• 2008

This paper analyses magnetic flux saturation of matching transformer considering characteristic of dynamic voltage restorer(DVR) system to solve voltage sags which are considered the dominant disturbances affecting power quality. This DVR consist of PWM inverter to inject arbitrary voltage, LC low pass filter and matching transformer for isolation and grid connection. However, the matching transformer has an excess of inrush current by magnetic flux saturation in the core of transformer. Due to this inrush current, the rating of matching transformers is double for needed nominal rating for protection of DVR. Therefore, in this paper, an advanced modeling method of magnetic flux saturation is used to analyze a magnitude and characteristic of magnetizing current. Simulation and experimental results considering characteristic of DVR system are provided to demonstrate the validity of the proposed analysis method.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.428-431
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• 2006

Matching transformer in Dynamic Voltage Compensator is needed for grid connection and isolation. Flux saturation in transformer will be occurred by voltage of transformer from inverter and DC offset voltage and flux saturation makes over current in transformer. In this paper, mathematical modeling of matching transformer is proposed for flux saturation simulation of Dynamic Voltage Compensator.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.879-884
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• 2009

A Method for detection of saturation of a current transformer(CT) is proposed. The algorithm is initiated when the end point of a saturation period is detected. This detection is achieved by checking the time interval between the adjacent zero-crossing points of the second derivative of the secondary current. Once the end point of the saturation period is detected, the beginning point of the corresponding saturation period is determined by backward examination of the sum of the secondary current from the end point. The performance of the algorithm was evaluated for a-g faults on a 345 kV 100km overhead transmission line. The Electromagnetic Transient Program(EMTP) was used to generate fault current signals for different fault inception angles and different remanent fluxes. The performance evaluation shows that the proposed algorithm successfully detects the saturation period even in the presence of a remanent flux.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.7
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• pp.781-786
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• 2015

In this paper, we analyzed characteristic of window type current transformer and we performed the optimal design consider to the loss; in order to design the current transformer figured signal of overcurrent warning circuit. The core size of window type current transformer was determined by the secondary coil turns. We analyzed current waveform, which is appeared by the number of coil turns on the core, we made sure the relation of secondary coil turns and load resistance in order to improve the non-sinusoidal wave by the flux saturation of the current transformer core. Additionally, we did improvement of the accuracy and optimal design through the transformation of the inner diameter and the stack length when the outer diameter of core is sustaining.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.3
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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

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.9
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• pp.150-158
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• 2010

We had experienced the several system failures which were concerned about zero sequence voltages at the tertiary side of 345[kV] transformers. In this paper, we had considered the zero sequence voltage and its reduction methods at the 345[kV] auto-transformer tertiary. For analysis, we used EMTP(Electro-Magnetic Transients Program). The calculation results by EMTP were compared with the measured data of the field tests. From the calculation and the field tests, we had verified that it is due to pre-saturation characteristics of the potential transformer. So, we had improved its saturation characteristics and applied it at real site. After improvements, we could reduce the zero sequence voltage below the setting level of the 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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• 2002.11b
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• pp.50-52
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• 2002

Distance relays need accurate current and voltage for determining the trip ignition. Therefore we must analyze nonlinear phenomena which cause distortion in signals first of all. This paper presents the effect of some distortion(arcing fault and current transformer saturation) in power system. The saturation of a current transformer distorts input current of a distance relay and arcing faults make current and voltage to be changed. This paper describes modeling methods of a current transformer and arcing faults, and describes the simulation result of two distance relay algorithms (discrete fourier transform and modified differential equation methods)

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.157.2-157
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• 2001

This paper describes the synergism of Artificial Neural Network and Fuzzy Logic based approach to improve the reliability of transformer differential protection, the conventional transformer differential protection commonly used a harmonic restraint principle to prevent a tripping from inrush current during initial transformer´s energization but such a principle can not performs the best optimization on tripping time. Furthermore, in some cases there may be false operation such as during CT saturation, high DC offset or harmonic containing in the line. Therefore an artificial neural network and fuzzy logic has been proposed to improve reliability of the transformer protection relay. By using EMTP-ATP the power transformer is modeled, all currents flowing ...