Review on Operation Fault of High-voltage Power Transmission Lines and Effective Prevention Countermeasures

Cunxu Wang,Xiaolin Sun,Xiaoyu Sun,Xinxing Chi 보안공학연구지원센터 2015 International Journal of Smart Home Vol.9 No.7

In the power system, transmission line as a guarantee for effective power supply, takes charge of the transmission from output power of substation to the consumers. The present study mainly focuses on the fault of transmission line resulted from external uncertainties, such as lightning, wind age yaw, ice coating and bird damage, as well as internal factors of high-voltage transmission line, including the grounding and short circuit. Accordingly, fault diagnosis and protecting measures on the high-voltage transmission line are proposed with advices on the improvement of operation and maintenance management of the line to reduce the fault frequency of the transmission line in the process of operation at a greater extent and to ensure the power supply stability of the whole power grid system to the user.

임펄스 측정을 위한 고속 고전압 용량성 분압기 설계

이재호,이건아 한국철도학회 2019 한국철도학회논문집 Vol.22 No.7

In this paper, a high-speed, high-voltage capacitive voltage divider (CVD) for impulse measurement wasdesigned and fabricated. The impulses generated during accidents such as railway applications are generated by waveformswith high rise time and high peak value. The voltage divider has been improved on the basis of a CVD. A CVDhas a large partial voltage ratio and is suitable for high voltage applications; it has a simple structure. Designed to meetthe target voltage, the circuit is designed for fast rise time by reducing the stray inductance. The fabricated CVD wasverified under various conditions in comparison with a commercial probe. Experimental results show good results in theform of high measured voltage and rising waveform. Device can be applied to research into high voltage impulse applicationsthat have rapid rise time, such as lightning, accident current, etc.

A Study on Optimization of Compact High-voltage Generator Based on Magnetic-core Tesla Transformer

Jeong, Young-Kyung,Youn, Dong-Gi,Lee, Moon-Qee The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.4

This paper presents a compact and portable high-voltage generator based on magnetic-core Tesla transformer for driving an UWB high power electromagnetic source. In order to optimize the performance of the high-voltage generator, a novel open-loop cylindrical magnetic-core adopting the quad-division lamination structure is proposed and manufactured. The designed high-voltage generator using the proposed magnetic core has a battery-powered operation and compact size of $280mm{\times}150mm$ in length and diameter, respectively. The high-voltage generator can produce a voltage pulse waveform with peak amplitude of 450 kV, a rise time of 1.5 ns, and pulse duration of 2.5 ns at the 800 V input voltage.

고전압 입력용 SMPS의 고효율 전략

우동영,박성미,박성준 한국산업융합학회 2019 한국산업융합학회 논문집 Vol.22 No.3

Recently, the demonstration and research on the power transmission using high voltage DC such as HVDC(High Voltage DC), Smart Grid, DC transmission and distribution have been actively conducted. In order to control the power converter in high-voltage DC power transmission system, SMPS(Switching Modulation Power Supply) for power converter control using high-voltage DC input is essential. However, the demand for high-pressure SMPS is still low, so the development is not enough. In the low-output SMPS using the high-voltage input, it is difficult to achieve high efficiency due to the switching transient loss especially at light load. In this paper, we propose a new switching scheme for high power SMPS control for low output power. The proposed method can provide better efficiency increase effect in the light load region compared to the existing PWM method. To verify the feasibility of the proposed method, a 40 W SMPS for HVDC MMC(Modulation Multi-level Converter) was designed and verified by simulation.

Development of a Pulsed Magnet System

손광효,S. H. KIM,Z. H. JANG,서병진 한국물리학회 2014 새물리 Vol.64 No.6

We report the development of a high-voltage-capacitor-discharge-type pulsed magnet system generating a magnetic field of higher than 30 T. It is composed of a magnet solenoid, a capacitor bank, a high-voltage high-current switching unit, a high-voltage capacitor-charging DC power supply, and a magnet-cooling liquid-nitrogen dewar. The capacitor bank is composed of 10 units of 9 kV 830 μF pulse capacitors. The switching unit is composed of a high-voltage SCR (silicon controlled rectifier) with a surge current capacity of 65 kA and a maximum voltage of 8.5 kV. The maximum output voltage of the high-voltage DC power supply is 10 kV, and the maximum charging current is 0.5 A. From a test with a calibrated induction magnetometer, the maximum field is found to reach ~30 T at a charging voltage of 4 kV. The duration of the pulse is 50 ~ 200 ms, depending on the crowbar's resistance value. The diode circuit can easily be modified to switch between a full-wave mode and a half-wave mode. Results on the training of the magnet is also reported.

Investigation on aerodynamic instability of high-voltage transmission lines under rain-wind condition

Chao Zhou,Yibing Liu,Zhiyong Ma 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.1

Under rain-wind conditions, rain-wind induced aerodynamic instability phenomenon often occurs on high-voltage transmission lines. Like the effects of any other oscillations, this kind of vibration intensifies the fatigue of high-voltage conductors, especially on line supportsor clamps. The presence of raindrops and wind associated with electric field maybe the main cause of this phenomenon. On rainydays, raindrops hit the transmission line and suspends to the high-voltage conductor. The suspended raindrops form upper rivulet andlower rivulet and take an elliptical arch shape along the surface of the high-voltage conductor by action of the wind, if rainfall is sufficient. Moreover, the rivulets are enlarged as a cone shape with the electric field of high-voltage conductor. The upper rivulet’s effect onthe original cross-section formation of the high-voltage conductor and its movement are likely to be the cause of aerodynamic instability. The objective of this paper is to validate a two-dimensional model to investigate the effects of different parameters (electric field strength,wind velocity, frequency and damping ratio of the dynamic system) on aerodynamic stability of the conductor. The Lyapunov stabilitytheory is applied to the model to derive the criterion for the instable angle of the rivulet. Moreover, an experimental conductor modelwith a moveable artificial upper rivulet is set-up and tested in a wind tunnel. The theoretical results are in good agreement with the experimentaldata. The model enable better comprehension of the rain-wind induced aerodynamic instability on the conductor.

고효율 및 슬림형 전압 평형 3-레벨 벅 컨버터

정준봉,김찬규,하가산,우원명,강정일,한상규 전력전자학회 2023 전력전자학회 논문지 Vol.28 No.2

The 3-level buck converter features half the switch voltage stress of the conventional synchronous buck converter. The operating frequency of the output inductor is also twice the switching frequency. The slope of the inductor current can be reduced as well due to the flying capacitor voltage, which can greatly reduce the size of the output inductor. Therefore, the 3-level buck converter can achieve high efficiency and high power density. The flying capacitor voltage must be half the input voltage to achieve the abovementioned strength. Most conventional control schemes for the voltage balance of the flying capacitor adopt a peak or valley current mode control method using real-time current sensing. Therefore, the control algorithm is complicated, and high performance and expensive digital controller is required. This study proposes an independent two-loop voltage mode control scheme that can guarantee the flying capacitor voltage to be half of the input voltage. The proposed control scheme can be simply implemented without current detection and does not require complicated control algorithms. Thus, simple and low-cost micro controller can be used. Experimental results from a rated prototype of 500 W are provided to verify the performance of the proposed control scheme.

A Study on Optimization of Compact High-voltage Generator Based on Magnetic-core Tesla Transformer

Young-Kyung Jeong,Dong-Gi Youn,Moon-Qee Lee 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.4

This paper presents a compact and portable high-voltage generator based on magneticcore Tesla transformer for driving an UWB high power electromagnetic source. In order to optimize the performance of the high-voltage generator, a novel open-loop cylindrical magnetic-core adopting the quad-division lamination structure is proposed and manufactured. The designed high-voltage generator using the proposed magnetic core has a battery-powered operation and compact size of 280 mm × 150 mm in length and diameter, respectively. The high-voltage generator can produce a voltage pulse waveform with peak amplitude of 450 kV, a rise time of 1.5 ns, and pulse duration of 2.5 ns at the 800 V input voltage.

Study on High Resistance Distance Relay in Directly Earth System

Liu, Huan-Zhang,Li, Ying-Hong The Korean Institute of Electrical Engineers 2011 The Journal of International Council on Electrical Vol.1 No.4

The coverage of transition resistance and the avoidance of load impedance is in essence a contradiction for distance protection. It's evident from the impedance plane that the requirement to avoid the load impedance results in that the action space of the distance relay is greatly limited, which accordingly reduces the ability of the relays to cover the transition resistance. In fact, there are some limitations to analyze the distance relays in the impedance plane. It would be better in the voltage plane. The three elements of distance relay in the voltage plane are the polarization voltage, operation voltage and operation characteristic, of which the polarization voltage is most important. The relay could ideally select pre-fault voltage as polarization voltage, while it practically employs the positive voltage. The difference between the two kinds of polarization voltage is negligible in the state of low impedance ground fault, while significant in the state of high impedance ground fault. Thus, this paper uses the memory and the non-fault phase parameters to gain the pre-fault voltage, that is, the new polarization voltage, and puts forward a new self-adaptive high impedance ground distance relay.

Experimental Study on High Voltage Gain DC-to-DC Boost Type Converter EmployingSwitched-Inductor

오만석,문은아 조선대학교 공학기술연구원 2018 공학기술논문지 Vol.11 No.2

The high boost dc-dc scheme is one most of the topic that attracted the attention of researchers because they have some merits over the conventional boost converter. Recently, a high gain DC-to-DC boost type converter has been introduced by employing switched-inductor. The high gain DC-to-DC boost type converter topology is suitable for high gain conversion applications where a varying low dc input voltage is converted to a high stabilized dc output voltage. In the paper, the experimental results of the novel high gain DC-to-DC boost type converter employing switched-inductor are illustrated. Furthermore, an extended high gain DC-to-DC boost type converter is also proposed. Circuit analysis, operating theories of the extended high gain DC-to-DC boost type converter are presented. Finally, the experimental results of the high gain DC-to-DC boost type converter are also presented to validate the performance of the high gain DC-to-DC boost type converter for the practical implementation.