• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.3
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• pp.111-115
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• 2012

Generally, brushless DC motor(BLDCM) driving system uses hall sensors or encoders as the mechanical position or speed sensor. It is necessary to achieve the informations of rotor position for driving trapezoidal type brushless DC motor without any position sensor. In this paper, the commutation signals are obtained without the motor neutral voltage, multistage analog filters, A/D converters, or the complex digital phase shift circuits which are indispensable in the conventional sensorless control algorithms. In the proposed method, in stead of detecting the zero crossing point of the nonexcited motor back electromagnetic force for the average motor terminal to neutral voltage, the commutation signal are extracted directly from the specific average line to line voltage with low-pass filter, adder and comparators circuit. In contrast to conventional methods, the neutral voltage is not need; therefore, the commutation signals are insensitive to the common mode noise. Moreover, the complex phase shift circuit can be eliminated. The effectiveness of the proposed method is verified through simulation results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.35-40
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• 2007

The one step type and two step type pole are used in distribution line. If the three phases are not balanced, the communication line can be damaged by induced voltage. This paper calculates the neutral current using KEPCO's distribution system model which is only composed by one step type pole. The used system model is modelled by using ATPDraw and the neutral current is calculated by using EMTP/MODELS. Many cases for abstracting the neutral current characteristics in KEPCO's distribution system are simulated and analyzed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.169-174
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• 2005

The conventional harmonic filters to reduce zero harmonic current from neutral reactors and Zig-Zag connection, have several disadvantages of the decreased reduction rate of harmonics under a light load, because they have the load factor-dependent reduction rate of harmonics, and the risk of potential breaking in the neutral line by heated neutral reactor. Based Zig-Zag connection and Open-Delta mode, this new harmonic eliminating device (HANOS) adopts the combination of Zig-Zag connection and Open-Delta mode-the latter is additionally applied to the transformer's core block for connection to the neutral line. The results of this study demonstrated that the new device could eliminate safely zero harmonic current running in the neutral line without heating.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1459-1467
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• 2011

This paper proposes the effective method to improve the protection from induced lightning Surge by making common grounding from individual grounding. Common grounding under equipotential principle is more effective than individual grounding for lightning Surge protection, and so common grounding is indicated as international technical standard under the AC power supply system with neutral line. So, this paper is to propose the effective way of induced lightning Surge protection method for currently installed power supply system which has no neutral grounded line and individual grounding which are weak for lightning Surge protection. This proposal can improve the power supply system as has neutral line, and improve the grounding system to common grounding system. And also this paper proposes to make effective equipotential system with voltage variable shunting devices for lightning Surge protection.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.215-218
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• 2013

This paper proposes the effective method to improve the protection from induced lightning surge by making common grounding from individual grounding. Common grounding under equipotential principle is more effective than individual grounding for lightning surge protection, and so common grounding is indicated as international technical standard under the AC power supply system with neutral line. So, this paper is to propose the effective way of induced lightning surge protection method for currently installed power supply system which has no neutral grounded line and individual grounding which are weak for lightning surge protection. This proposal can improve the power supply system as has neutral line, and improve the grounding system to common grounding system. And also this paper proposes to make effective equipotential system with voltage variable shunting devices for lightning surge protection.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.510-512
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• 2000

This paper describes the voltage induced at neutral line and the proper location of lightning arrester in combined 22.9 kV class distribution line jointed overhead line and cable each other Modeling is established in ATP Draw to perform simulation. Simulated distribution line at this paper consists of distribution line 4.2km and underground distribution line 2km. Overvoltage and induced voltage are analyzed at several point of combined line. Analysis results was compared to select the best point to install arrester. Such analysis technology will be applied to obtaining capacity and location of arrester in the similar combined distribution line.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.689-696
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• 2018

System grounding is applied to the neutral point of a power source to secure the from any abnormal voltage and/or grounding fault. System grounding, which is applied mainly in ships is an ungrounded and resistance grounded system. Vessels using the MV power system with 3.3kV, 6.6kV, and 11kV mainly adopt a high resistance grounding system among the resistance grounding systems. The ground fault accounts for 95% of all faults occurring in the electrical system and when a fault occurs, the line-to-ground voltage of the power system is increased excessively, which adversely affects the onboard insulation system. This study analyzed the variation characteristics of the line-to-ground voltage neutral point according to the degree of ground fault in a resistance ground system applied in vessels. For this purpose, the characteristics of the grounding system were first explained, and the modeling of the neutral point potential of the line-to-ground voltage of the resistance grounding system in the vessels was derived. Finally, this study examined how the line-to-ground voltage, line voltage, and neutral point change according to various variable environments through MATLAB simulations.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.103-106
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• 2008

OPNW, which takes charge of the outer neutral wire role and the inner optical network role, was developed at the first time among nation and substituted the neutral wire of distribution line between electric power substation and neighboring station. This paper refers to results about its optical character measured periodically, and examines closely whether the unique matter will be occurred or not about the role of neutral wire during more than one year. Also, established OPNW became a new chance to distribution facility's working by establishing remote portrait supervisory system and doing remote supervisory about essential equipment of distribution line.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.87-89
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• 2005

If the three phases are not balanced, the current in neutral line is not zero. Then, the induced voltage can be generated In communication line. The KEPCO's rule about unbalanced current in single electric pole is a twenty percent of phase current. But the unbalanced current in double electric pole can't decide the rule because there are many different views. This paper develops the calculation and analysis technique of neutral current in single electric pole and double electric pole using equivalent circuit analysis, vector analysis and EMTP simulation.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2212-2213
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• 2008

In this paper, we studied the method for simultaneous quenching of a transformer type superconducting fault current limiter (SFCL) with two superconducting elements connected in series. Only an element between two elements of the transformer type SFCL was quenched like the case of the resistive type SFCL. By this quenching characteristics, the power burden of the superconducting element was increased. In order to solve this problem, we connected the neutral line between two superconducting elements and the center of secondary coils. The two elements were all quenched in the transformer type SFCL with a neutral line. As a result, the power burden of superconducting elements was decreased, so it was efficient for the increase of power capacity of the transformer type SFCL.