전원용 SPD의 건전성 평가 장치 개발

장석훈 ( Sughun Chang ),김영진 ( Youngjin Kim ),김성주 ( Sungju Kim ),김재형 ( Jaehyung Kim ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.4

This paper deals with development of integrity evaluation instrument for the power line surge protective device. A reliable power supply is an essential element in the developed information and communication society by highly advances in IT technology. However, the lightning incidence also increased with the recent extreme weather events. In Korea, in order to protect the electrical system from lightning surge, SPD(Surge Protective Device) has been used for these past 30 years. However, the method of diagnosing the safety of the SPD in the industry is insufficient. In this paper, SPD integrity evaluation system was composed of a variable DC power source unit, voltage-current sensor and the embedded controller. In order to measure V-I characteristics of MOV, 3 type samples were degraded by impulse current generator. After impulse tests, the varistor voltage of all samples and nonlinearity coefficient were decreased. It confirmed the utility of the developed equipment by this experimental test and the reliability of SPD is expected for surge accident prevention when applied to industrial plant.

Experimental Research on Impulse Breakdown Characteristics of Soil

Jaebok Lee,Sughun Chang,Sungho Myung,Yuengue Cho 대한전기학회 2004 KIEE International Transactions on Electrophysics Vol.4C No.2

Fast Evaluating the Electromagnetic Fields Generated by a Vertical Electric Dipole Over the Lossy Ground Using Sommerfeld Integral Without Truncation

Jaebok Lee,Jun Zou,Jing Wan,Sughun Chang IEEE 2011 IEEE transactions on electromagnetic compatibility Vol.53 No.4

<P>The electromagnetic fields generated by a vertical electric dipole, expressed in the form of the Sommerfeld integral, are important in the study of lightning. In this paper, an algorithm, which can analytically approximate the Sommerfeld tail integral, is proposed. Due to the fact that the tail integral is expressed by a sum of several error functions, the tail integral of a vertical electric dipole can be evaluated without the truncation of the infinite upper limit. The comparison indicates that the results calculated by the proposed algorithm are accurate, and the computational time, compared to the one using direct numerical quadrature method, is much shorter.</P>

Calculation of the Earth Return Impedance of a Conductor Inside a Tunnel by Using the Fictitious Medium Method

Jun Zou,Jaebok Lee,Yafei Ji,Sughun Chang Institute of Electrical and Electronics Engineers 2007 IEEE transactions on power delivery Vol.22 No.4

<P>This paper describes an efficient numerical approach for the calculation of the per-unit length earth-return impedance of a conductor inside a tunnel. The influence of the tunnel on the per-unit length impedance is replaced by a set of equivalent current sources via the fictitious medium method. The main advantage of the proposed approach is that it can solve the boundary value problem within the tunnel region. The proposed method can reduce the calculation region and, thus, leads to time savings. A comparison of the numerical results with published data shows very good agreement. The proposed method is a good candidate for impedance calculation of a conductor inside a tunnel.</P>

Calculation of the Magnetic Field in Air Produced by the Underground Conductor Using Pollaczek Integral

Jun Zou,Mo Li,Jaebok Lee,Sughun Chang IEEE 2012 IEEE transactions on electromagnetic compatibility Vol.54 No.1

<P>A fast approach for evaluating the magnetic field in air generated by an underground conductor is proposed in this paper. By means of the asymptotic extraction technique, the magnetic field can be decomposed into two parts. One is the contribution from the asymptotic integrand, which can be calculated analytically; and the other can be expressed by a sum of the definite integral and the exponential integrals. Due to the fact that there is no improper integral involved, the approach proposed here is highly efficient. Meanwhile, the impact of the eddy current to the magnetic field is quantitatively analyzed. The proposed approach could be used in the electromagnetic environment assessment for underground power cable systems.</P>

GIS 진단시스템의 평가를 위한 PD 모의 펄스발생기 개발에 관한 연구

김성주,장석훈,조국희,Kim, Sungju,Chang, Sughun,Cho, Kook-hee 한국안전학회 2018 한국안전학회지 Vol.33 No.2

The expansion and stable operation of electric power facilities are important factors with development of industrial facilities in modern society. In high-voltage equipment such as GIS, the insulation characteristics may be deterioated by environment-friendly gas adaption and miniaturization. There is also the possibility of accidents due to insulation breakdown due to the deterioration of power facilities. Therefore, it is necessary to extend the diagnosis system to continuously monitor the danger signals of these power equipment and to prevent accidents. Most of the internal defects in the GIS system are conductive particles, floating electrode defects, protrusion defects, and the like. In this case, a partial discharge phenomenon is accompanied. These partial discharge signals occur irregularly and various noise signals are included in the field, so it is difficult to evaluate the reliability in the development of the diagnostic system. In this paper, a study was made on equipment capable of generating a partial discharge simulated signal that can be adjusted in size and frequency to be applied to a diagnostic device by electromagnetic wave detection method. The PD simulated pulse generator consists of a user interface module, a high-voltage charging module, a pulse forming circuit, a voltage sensor and an embedded controller. In order to simulate the partial discharge phenomenon similar to the actual GIS, a discharge cell was designed and fabricated. The application of the prototype pulse generator to the commercialized PD diagnosis module confirmed that it can be used to evaluate the performance of the diagnostic device. It can be used for the development of GIS diagnosis system and performance verification for reliability evaluation.

A Hermite Interpolation Model to Accelerate the Calculation of the Horizontal Electric Field of a Lightning Channel Along a Transmission Line

Jun Zou,TaoBin Jin,WenWen Li,Jaebok Lee,Sughun Chang IEEE 2013 IEEE transactions on electromagnetic compatibility Vol.55 No.1

<P>The radiated horizontal electromagnetic field of a lightning channel acts as the excitation when the lightning-induced voltages on overhead lines are under study. To accelerate the calculation of the horizontal electric field of a lightning channel, a piecewise Hermite interpolation model is proposed, which exploits the distinct feature of the transmission line whose height keeps unchanged. In the piecewise Hermite interpolation model, the key technique is fast evaluating the derivative of the horizontal electric field expressed by the generalized Sommerfeld integral. In this paper, the moment technique is utilized to calculate the derivatives efficiently. As demonstrated in the numerical examples, the piecewise Hermite interpolation model can reach a high accuracy with a very low computation cost.</P>

Evaluating ground fault current distribution on overhead transmission lines using an iterative nodal analysis

Zou, Jun,Lee, Jae-bok,Li, JunJie,Chang, Sughun Emerald Group Publishing Limited 2011 Compel Vol.30 No.2

<B>Purpose</B> - The purpose of this paper is to present an original iterative nodal approach to calculate the fault current distribution on overhead lines. <B>Design/methodology/approach</B> - By changing the mutual couplings among different conductors into the equivalent voltage sources, node voltages are updated iteratively by using conventional nodal analysis with those additional sources until the convergence is achieved. <B>Findings</B> - The proposed algorithm can handle the complicated topology of a power transmission line and has no difficulties in taking all physical couplings into account. The fault current distribution calculated by this method is in good agreement with those published in the literature. Although the proposed approach is iterative, the CPU time needed is still reasonable compared to the direct solution approach. The memory requirement is low because the coefficient matrix is highly sparse for the nodal analysis of each iteration loop. <B>Originality/value</B> - The proposed approach can serve as an alternative in calculating the fault current because of its efficiency and ease of implementation.

Fast evaluation of the lightning electromagnetic field in the time domain with an adaptive piecewise approximation of channel base current

Lee, Jae-bok,Zou, Jun,Li, Mo,Chang, Sughun Emerald Group Publishing Limited 2013 Compel Vol.32 No.3

<B>Purpose</B> - A fast algorithm is proposed to calculate the lightning electromagnetic field over a perfectly conducting earth surface. <B>Design/methodology/approach</B> - The channel base current is approximated by a number of sub-domain quadratic functions using the proposed adaptive sampling technique, and the derivative and integral of the channel base current with respect to time can be analytically expressed. With the help of these approximations, the ideal electromagnetic field of the lightning channel can be evaluated along the lightning channel with respect to the height. <B>Findings</B> - The computational time can be greatly reduced using the proposed approach to evaluate the electromagnetic field of a lightning channel in the time domain. <B>Originality/value</B> - The adaptive sampling technique is a general-purposed approach, which can be potentially used in other applications to fit a function with the minimal number of intervals.

Evaluation of the horizontal electric field of the lightning channel with the fast convergent sommerfeld integral tail

Zou, Jun,Zhou, Chenglong,Li, Wenwen,Lee, Jae-bok,Chang, Sughun Emerald Group Publishing Limited 2013 Compel Vol.32 No.6

<B>Purpose</B> - The electromagnetic field radiated from a lightning channel is the excitation for analyzing the field-to-transmission line coupling problem. The purpose of this paper is to propose a novel efficient approach to evaluate the horizontal electric field of the lightning channel expressed by the generalized Sommerfeld integral. <B>Design/methodology/approach</B> - The asymptotic integral is extracted from the original one, which actually makes the Sommerfeld integral tail reach its convergence very quickly. To handle the sharp variance around k0, a closed-form integral, which is obtained by replacing the original kernel with an approximated function, is presented in detail. The numerical examples validated the proposed approach in the both frequency and time domain. <B>Findings</B> - The approach proposed in this paper has been validated by the comparison with results in other papers. The agreement among these results reaches very well, and the approach proposed in this paper is more efficient and easy to implement, especially for the calculation of the tail integral part. <B>Originality/value</B> - In accordance with the numerical experiments, the proposed approach can be served as a qualified candidate in terms of computational efficiency to evaluate the electromagnetic field generated by the lightning channel.