• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.257-263
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• 2016

This paper describes the lightning arrester transients in cable head termination. The installation references of cable head tower and lightning arresters are firstly reviewed, then the performance of lightning arrester operation is also evaluated based on lightning overvoltage analysis by the change of grounding lead cable length. This paper finally proposes the optimal length of grounding lead cable at the cable head termination. The limited lightning current is also proposed according to the change of grounding lead cable length. The results will contribute to protecting insulation breakdown failure against lightning surge at the terminations and joints.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1503-1510
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• 2007

To implement a high-precision lightning tracking system utilizing TDOA measurements, high-speed data acquisition and precise timing synchronization between ground sensors should be achieved. At the same time, considering the size of digitizer's memory, the data memory needs to be managed so that only the sampled data around the occurrence of stepped leader pulse is stored. This paper presents a detection-and-acquisition system for lightning signals that is the main equipment of ground sensor in lightning tracking system. GPS clock module is used to get precise timing synchronization and the 500MHz high speed digitizer is employed. In order to detect the leading edge of the lightning pulse and save the sampled data and its timing, lightning detection module is implemented and multi-record method is employed in the proposed system. Field experiment results show that the proposed system can detect and save the lightning signal efficiently.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.2
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• pp.191-196
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• 2010

The electricity distribution system in Korea is adopting a multi-grounding system. Protection of this distribution system against lightning is performed by installing overhead ground wires over the high voltage wires, and connecting the overhead ground wires to the ground every 200 m. The ground resistance in this system is limited not to exceed $50\Omega$ and overhead ground wire and neutral wire are multiple parallel lines. Although overhead ground wire and neutral wire are installed in different locations on the same pole, this circuit configuration has duplicated functions of providing a return path for unbalanced currents and protecting the distribution system against induced lightning. Therefore, the purpose of this study is to analyze the induced lightning shielding effect according to the neutral wire installation structure of a 22.9kV distribution line in order to present a new 22.9kV distribution line structure model and characteristics. This study calculated induced lightning voltage by performing numerical analysis when an overhead ground wire is present in the multi-grounding type 22.9kV distribution line structure, and calculated the induced lightning shielding effect based on this calculated induced lightning voltage. In addition, this study proposed and analyzed an improved distribution line model allowing the use of both overhead wire and neutral wire to be installed in the current distribution lines. The result of MATLAB simulation using the conditions applied by Yokoyama showed almost no difference between the induced lightning voltage developed in the current line and that developed in the proposed line. This signifies that shielding the induced lightning voltage through overhead wire makes no difference between current and proposed distribution line structures. That is, this study found that the ground resistance of the overhead wire had an effect on the induced lightning voltage, and that the induced lightning shielding effect of overhead wire is small.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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• pp.82-88
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• 2013

It is important to give lightning warning prior to a cloud-to-ground (CG) discharge within an Area of Concern (AOC) because most of lightning damage and victim are usually occurred by the first lightning in the AOC. The aim of this study is to find the optimal operation conditions of the automated lightning warning systems in order to make the best use of the available data. In this paper, the test-operated results of the automated lightning alert and risk management system (ALARM) based on detections of CG discharge and eletrostatic field and optimized at probability of lightning have been described. It was possible to obtain the following warning performance parameters: probability of detection (POD), false alarm ratio (FAR), probability of lightning (POL) and failure-to-warn rate (FTW). The data obtained from trial operation for 5months were not sufficient but the first analysis of domestic lightning warning was carried out. We have observed that the evaluated statistical results through trial operation depend on the various factors such as analysis methods and criteria, topographical conditions, etc. Also we suggest some methods for improvement of POL and POD including the finding of the optimal electric field threshold level to be used, based on the high values of FAR and FTW found in this work.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.11
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• pp.532-537
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• 2006

Lightning induced faults accounts for more than 66% at the transmission lines of KEPCO. The lightning causes damages to power system equipments including transmission line, the blackout of electricity and the electro-magnetic interference. Because of this reason, we need the real time lightning information for the optimal operation of power system. And, it is required to obtain and accumulate the lightning current parameters for the insulation design. In 2005, KEPRI constructed a lightning detection network, the KLDNet (i.e. Kepco Lightning Detection & Information System) and launched a lightning information service for KEPCO customers. It is intended to provide data service on the operation of transmission lines and collect lightning-related data, which is the most important factor regulating power system design and operation. The new system will replace LPATS, the old detection system, which has been operating since 1995 and is rapidly failing in terms of both detection performance and location accuracy. The purpose of this paper is to explain the work performed and the results of that work in performing a site survey of several locations. The purpose of the site survey is to find locations acceptable for the installation of a lightning location receiver in support of a Lightning detection system(LDS). A restriction was placed on the surveyed locations, as they must belong to the Korea Electric Power Company. This requirement was made to facilitate the communication needs of the LDS network. Total of 15 sites were evaluated as possible LDS sensor sites. Some of the sites were rejected for physical reasons and therefore no electrical testing was performed. Of the 15 sites, total of 10 sites were considered acceptable and 5 sites were rejected for various reason. In this paper, we would like to explain the site survey and detection efficiency for LDS.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.459-465
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• 2017

In this paper, we introduce the design consideration of the lightning induced transient protection circuit for the indirect lightning strike on the avionics equipment. The lightning induced surge voltage, which is so-called as indirect effects of lightning, may cause a functional failure or physical damage to the electrical and electronic equipment of aircraft. In order to protect the electrical and electronic equipment of aircraft from the indirect effects of lightning, we should analyze the effect of lightning strike on aircraft and consider applying protection design for each avionics device. However, lightning induced transient protection circuits can have unintended consequences because parasitic inductance elements are exist in PCB and TVS diodes. In this paper, we introduce the design method of the protection circuit considering the parasitic inductance of the protection circuit. In addition, we show the result of verification test performed to validate the protection circuits for indirect effects of lightning.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.824-831
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• 2013

Lightning electromagnetic fields are important issues for the evaluation of lightning induced overvoltage on power lines and for setting the appropriate protection level for power networks. Such electromagnetic fields are strongly dependent on lightning return stroke currents at different heights along the lightning channel. On the other hand, the ground reflection factor due to the difference between the return stroke channel impedance and the equivalent ground impedance at channel base can have an effect on the shape of the return stroke currents by entering additional reflected currents into the channel. In this paper, the effect of the ground reflection factor on the return stroke currents at different heights along a channel and the electromagnetic fields associated with the lightning channel at close distances are considered. Moreover, the behavior of the electromagnetic fields versus the reflection factor changes and the radial distance changes are considered and the results are discussed accordingly. The results illustrate that the reflection factor has a direct relationship with the values of the electromagnetic fields while this is usually ignored in earlier studies.

• Journal of the Korean earth science society
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• v.31 no.7
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• pp.749-761
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• 2010

A relationship between cloud-to-ground lightning and rainfall was investigated by using the two-years (2006-2007) summer lightning data and the automatic weather stations (AWSs) data of the Korea Meteorological Administration. The negative lightning occurred at the core of highly concentrated convection, which is often accompanied with heavy rains. Whereas most positive lightning occurred at the anvil cloud with low density and light rains. The rainfall intensity is strongest when the negative and positive lightning occurred concurrently, and one with lightning is much stronger than that without lightning. A portion of the positive lightning of the total lightning was less than 10% during summer seasons, and the lightning without rains was about 34%. The rain rate was strongly correlated with the negative flash rate, and the correlation coefficients varied between 0.87 and 0.94 according to the co-location radius (5-15 km) of AWSs. Most of the lightning occurred 10 minutes before and/or concurrently occurred with rains. A portion of the convective rainfalls of the total rainfalls was at least 20% when we define the rainfalls with lightning as convective. The convective rainfall was greater during August than in June and July. In general, the portion of convective rainfalls showed a maximum diurnal variation during late afternoon as in the rains and lightning.

• Journal of the Korean earth science society
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• v.30 no.2
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• pp.210-222
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• 2009

Lightning data, observed from total lightning detection system (TLDS) of KMA, for the recent five years (2002-2006) have been analyzed for temporal and spatial characteristics of frequency, intensity, duration, and flash rate. Lightning frequency varies largely with years (most frequent in 2006) and the lightning during the summer accounts for 75% of total flashes and only 0.6% of lightnings strike in cold season. In rainy season (JJAS), the ratio of positive flashes to negative ones is as low as 0.15, but it increases up to 0.98 in February. The seasonal variation of lightning duration is strongly linked with lightning occurrences, whereas flashes rates show weak seasonal variability. In a daily scale, lightning, on average, occurs more often at dawn (2 am, 5-7 am) and in the mid-afternoon (15 pm), and the lightning at dawn (around 5 am) is most intense during the day. The western inland areas md the West/South Sea show high lightning density during JJAS, whereas eastern part and the East Sea exhibit a low density of lightning. Considering the low ratio of positive flashes (0.15) for the whole analysis domain during summer period, Chungnam and Jeonbuk areas have a high ratio of flashes over 0.4. However, these should be analyzed with much caution because weak positive cloud-to-cloud discharges can be regarded as cloud-to-ground flashes. The western inland also exhibits long annual flash hours (15-24). And the W3st Sea has high flash rates as a result of large density and low flash hours. The most frequent time of lightning occurrence over most inland areas lies between mid-afternoon and early-evening, whereas mountainous and coastal areas, and the northern Kyoungki and Hwanghae provinces show the maximum lightning strikes in the morning and at dawn, respectively.

• Journal of the Korea Computer Graphics Society
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• v.22 no.3
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• pp.53-61
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• 2016

In this paper, we propose an algorithm for generating lightning paths, which are more realistic than those of random tree based algorithm and faster than a physically based simulation algorithm. Our approach utilizes physically based Dielectric Breakdown Method (DBM) and approximates the electric potential field dramatically to generate the lightning path. We also show a guide path method for the lightning to avoid obstacles in a complex scene. Finally, our method renders fast and realistic lightning by considering physical characteristics for the thickness and brightness of the lightning stream. Our result of the lightning path shares similarity to natural phenomenon by having about 1.56 fractal dimensions, and we can generate the lightning path faster than a previous physically based algorithm. On the other hand, our method is difficult to apply on the real-time games yet, but our approach can be improved by performing the path generation algorithm with GPU in future.