• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.255-263
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• 2014

In this paper, seismic fragility analysis of lightning arrester is performed using capacity spectrum method(CSM). Since seismic fragility analysis of structure with many structural members is required to calculate many inelastic responses for several tens or hundreds of ground motions, simple method such as CSM is more appropriate than response history analysis(RHA). In general, accuracy of seismic response evaluated by CSM is less than that by RHA. In order to increase accuracy of CSM, equivalent SDOF method and performance point calculation technique are applied to CSM. Seismic fragility method proposed by Shinozuka et al. is used. In order to evaluate site effect of ground motions on seismic fragility, 60 different site classification earthquakes are selected as input ground motions. From the seismic fragility curves of lightning arrester evaluated by CSM and RHA, it can be observed that the seismic fragility curves evaluated by CSM are very similar to those by RHA. Also, it can be observed that main seismic failure mode of lightning arrest is bushing breakage.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.6
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• pp.96-103
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• 1997

This paper deals with the malfunction characteristics of the earth leakage circuit breakers(ELBs) applied by a lightning impulse voltage. In the cases of the regulation of KS C 4613 and the simulated circuits with surge protection devices, the dead operation characteristics of the ELBs against lightning impulse voltages were experimentally investigated and discussed. As a result, all the specimens(ELBs) used in this work have a cutoff performance of the lightning impulse voltage when the differential mode surges were injected at the input terminals of the ELBs owing to a surge absorber installed at the power source side of amplification circuit. Four kinds of the specimens have brought about malfunction in the condition of the lightning impulse dead operation test defined in KS C 4613, and the malfunction voltages are relatively high and are about 5-6.5[kV]. In the case of the simulated test circuit with surge protection devicesthree kinds of the ELBs have led to malfunction. Also the voltage level causing the malfunction of the ELBs is decreased by operation of surge protection devices, and it ranges from 3 to 5(kV).

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.19-24
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• 2016

One of key parameters on lightning protection system design of electric, information and communication system is grounding impedance. Earth impedance includes numerous information about earthing performance of grounding system. This paper suggests grounding impedance measuring device which is comprised of wideband current source, voltage and current measuring components. We used IQ Demodulation to measure more accurate phase difference of voltage and current. The range of frequency is up to 1 MHz that is IEEE defined as the range of lightning surge. We compared developed grounding impedance measuring device with existing one to test its performance, and we used grounding system while we implemented measurement and analysing by using fall of potential method IEEE Std.81 proposed.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1464-1465
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• 2007

The purpose of this paper is to identify the requirements for Surge Protective Devices (SPDs) used in protecting telecommunication and signalling system. All of these systems may be exposed to the effects of lightning and power line faults, either through direct contact or induction. These effects may subject the system to overvoltages or overcurrents or both, whose levels are sufficiently high to harm the system. SPDs are intended to provide protection against overvoltages and overcurrents caused by lightning and power line faults. This paper describes tests and requirements which establish methods for testing SPDs and determining their performance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1471-1476
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• 2012

A study on the dielectric characteristics of the Glass Fiber Reinforced Plastic (GFRP) is important for designing a reliable high voltage superconducting machines such as transmission superconducting fault current limiters, superconducting cables, and superconducting transformers. In this paper, dielectric experiments of the GFRP under lightning impulse voltage are conducted in liquid nitrogen($LN_2$) according to various experimental conditions such as the thicknesses of the GFRP, the diameters of electrode systems and the pressures. The dielectric characteristics of the GFRP are analyzed by using a Finite Elements Method(FEM) according to various field utilization factors. It has been reported that the electrical insulation design of the GFRP would be conducted by considering the mean electric field intensity($E_{mean}$) distributed inside the GFRP. In this study, it is found that the dielectric performance of the GFRP could be explained by not only $E_{mean}$ but also the maximum electric field intensity ($E_{max}$). Finally, the empirical formulae of the GFRP to estimate an electrical breakdown voltage at sparkover under the lightning impulse condition are deduced. It is expected that the presented experimental results in this paper are helpful to design electrically reliable high voltage superconducting machines using the GFRP as an insulation material.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.343-346
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• 2009

The grounding system of low voltage power systems is TT grounding system in Korea. In order to follow the international standard, TN grounding system is adopted. However, the performance of grounding systems has not been evaluated. This paper deals with the experimental results of protection ability of grounding system when lightning surge invades to the neutral line of low voltage power system. As a result, the TT grounding system is most frail for the lightning surge and it does not protect the electrical devices. On the other hand, the TN grounding system perfectly protects the electrical equipment and prevents the electric shock for human through the equipotential bonding. In case of TN system with supplement grounding, it is very important to lower the supplement grounding resistance to protect the electrical equipment and electric shock for human.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.119-125
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• 2009

This paper deals with the characteristics of soil ionization affecting the dynamic performance of grounding systems under lightning impulse voltage. A concentric hemispherical electrode system was employed in order to facilitate the field calculation and analysis of the experimental results. The parameters such as the ionization threshold and breakdown field intensity, the pre-ionization and the post ionization resistances, the time-lag to ionization, the transient impedance, the equivalent ionized radius for various soil media were measured and analyzed. The dynamic characteristics of ionization processes under lightning impulse voltage are strongly dependent on the types of soil and water content. As a result, a soil ionization reduces the ground resistance and there is a little effect of applied impulse polarity on the soil ionization threshold field intensity. Although the ionization threshold field intensity of wet clay with 30% water content is the highest, its ionized zone was found to be the smallest amongst the test samples.

• Journal of the Korean Society of Safety
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• v.31 no.1
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• pp.48-53
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• 2016

This paper deals with analysis of complex grounding system using electromagnetic simulation method. Electrical devices could be damaged by transient voltage such as a lightning surge. Therefore the measures to protect the equipments from transient, such as a lightning are required. The ground system is important in this respect. The representative parameter of grounding system performance is earth ground resistance. Precise prediction of earth resistance is required, because it is difficult to modify and change after the completion of the grounding system construction. Numerical modeling is often used in numerical analysis to identify the electrical characteristics of the grounding system. However complex systems are difficult to predict grounding characteristics by numerical analysis. If the total electric field of the earth in general is similar to the antenna model, in that the incident electric field and expressed as a sum of the scattering field. In this study, the electromagnetic field simulation tool "ANSYS HFSS" module containing the antenna model was used to analyze performance of ground system. Both the simple and complex grounding system were analyzed by simulation tool and experimental method. As a result simulation method is effective to predict performance of a complex ground system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.127-131
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• 2002

The surge protector is crucial power apparatus to guarantee the safe operation of power transmission of underground cable which can effectively restrain the overvoltage and inductive lightning stroke in power system. The surge protector is crucial power apparatus to guarantee the safe operation of power transmission of underground cable which can effectively restrain the overvoltage and inductive lightning stroke in power system. This paper described the results of a study on the performance for surge protector for underground cable. And, the performance of surge protector was evaluated through such as measurement of the reference voltage, residual voltage and impulse current etc. In results of surge protector, reference and residual voltage of ZnO element is 4.75 kV, 9.86 kV respectively. Also, In the impulse current test, thermal properties are good, despite of that polymeric housing of surge protector has thick structure. Therefore the developed surge protector is thought to apply for underground cable.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.162-168
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• 2009

This paper describes a study that is to redesign insulation of transmission lines and determine required the numbers of insulators in order to enhance the insulation performance of existing transmission lines which were constructed with standard insulation design, considering overvoltage analysis results, probabilities and characteristics of faults. To ensure proper insulation distance without deteriorating the required performance, EMTP model is established to calculate maximum overvoltage in the line. The fault records and predicted outage rates due to lightning and contamination in the line were investigated and analyzed respectively. It presents a method to determine the numbers of insulators considering the probability and the characteristic of fault.