Consequences of lightning strikes on nuclear power generating stations

The goal of this article is to investigate the effect of frequency-dependent soil models on the performance of grounding electrodes subjected to lightning strikes. Several soil models are examined while accounting for the variation of soil resistivity and permittivity as a function of the lightning current frequency spectrum. The analysis is performed for a homogeneous soil and a two-layer horizontally stratified soil. The impact of the frequency-dependent soil parameters on the ground potential rise (GPR) of simple grounding electrodes subjected to lightning is analyzed and discussed. The analysis is performed in the frequency domain and in the time domain. A wind turbine and its grounding system are also considered in this article. Special attention is given to the case of indirect lightning, rarely mentioned in the literature. The GPR of the grounding electrodes is examined when the frequency dependence of the soil is taken into account and the lightning channel is located at close distances to the electrodes. Indeed, the level of induced electromagnetic fields caused by a nearby lightning channel can still be too high and potentially dangerous. The computations are performed using an efficient Method of Moments (MoM) numerical tool based on surface-wire integral equations for a stratified medium in the frequency range from dc to several MHz. Numerical results demonstrate that the frequency dependency of the soil parameters results in a decrease of the potential rise of the grounding electrodes, with respect to the case where the parameters are assumed constant.

Influence of photovoltaic support on lightning transient under direct lightning strike

A tropical climate country experience high lightning related activities. This can be represented in terms of the keraunic level which lies within the region of 100 to 150 thunderstorm days per year. For a utility company, the high keraunic level would contribute to high possibility of power interruptions. These outages would ultimately lead to loss of revenue and reduced network reliability. These lightning related interruptions may be in terms of direct strikes to the line. Apart from that a consequent back flashover may result from an indirect lightning strike near the vicinity of the line. The aggregate of the direct and indirect lightning strikes would contribute to the overall lightning performance of the line. This paper outlines the application of a lightning performance analysis tool based upon the IEEE Std 1410-2004 conditioned for a tropical climate country. Results and analysis indicates factors that would affect the lightning performance of the line. The contributing factors found from these analyses would be dependent upon the environment at which the line is located, e.g. presence of tall objects which ultimately acts as a lightning shield would improve the lightning performance whereas if the lines are located in an open field, the probability of lightning strikes would be high. Based upon these factors, a list of possible mitigating actions is presented in improving the lightning performance of the line.

Significant differences have been identified in loss of offsite power (LOSP or LOOP) event description, category, duration, and applicability between the LOSP events used in NUREG/CR-6890 and ENS’ LOSP packages, which were based on EPRI LOSP reports with plant-specific applicability analysis. Thus it is appropriate to reconcile the LOSP data listed in the subject NUREG and EPRI reports. A cross comparison showed that 62 LOSP events in NUREG/CR-6890 were not included in the EPRI reports while 4 events in EPRI reports were missing in the NUREG. Among the 62 events missing in EPRI reports, the majority were applicable to shutdown conditions, which could be classified as category IV events in EPRI reports if included. Detailed reviews of LERs concluded that some events did not result in total loss of offsite power. Some LOSP events were caused by subsequent component failures after a turbine/plant trip, which have been modeled specifically in most ENS plant PRA models. Moreover, ENS has modeled (or is going to model) the partial loss of offsite power events with partial LOSP initiating events. While the direct use of NUREG/CR-6890 results in SPAR models may be appropriate, its direct use in ENS’ plant PRA models may not be appropriate because of modeling details in ENS’ plant-specific PRA models. Therefore, this paper lists all the differences between the data in NUREG/CR-6890 and EPRI reports and evaluates the applicability of the LOSP events to ENS plant-specific PRA models. The refined LOSP data will characterize the LOSP risk in a more realistic fashion.

Lightning protection and surge protection measures are essential for the availability of wind turbines and for their profitability. Whereas the electric and electronic equipment can be protected by a comprehensive surge protection concept, outer structures particularly the rotor blades are hit by direct lightning strikes. In defined maintenance cycles these damages are inspected and repaired in costly operations. In this paper a method for lightning current measurement is presented. It enables the operator to measure lightning currents directly and to determine their parameters like amplitude, current rise time and charge. The presented system with three sensor units is originally developed for wind turbines, to adapt maintenance cycle times to the real number of lightning strikes. Further applications in other industries are possible.

The paper studies the effect, a lightning strike has on a car electronic system. A direct lightning strike in the car cab are considered. The paper studies “KAMAZ” electromagnetic environment in a car cab and the electromagnetic interference in the interface-coupling path is given. The electromagnetic field in the inner space of the cabin can reach large values, which will lead to the disruption of the car electronic systems. The electromagnetic interference in the interface line and the power line connection will result in the physical destruction of transistors and integrated circuits. Recommendations to reduce electromagnetic interference and improve the immunity of car electronic systems are given.

Lightning overvoltages in low-voltage circuits in houses originating from a distribution line or an antenna have been actively studied. However, the mechanism by which damage is caused to home appliances due to a lightning strike to the ground near the house is still unclear. This paper discusses lightning overvoltages and currents in low-voltage circuits for various scenarios, such as a lightning strike to the ground, a direct strike to a distribution line, and a direct strike to an antenna. Simulations are carried out using the Electromagnetic Transients Program. From the simulation results, direct lightning strikes cause the most serious damage to home appliances, but nearby lightning strikes should also be considered when designing lightning protection schemes.

This paper discusses overvoltage transients in microgrid components resulting from lightning events. The microgrid components are exposed to overvoltage disturbances through direct and indirect lightning strikes which can result in insulation damage. Models that are available in literature for analyzing the electromagnetic transient response at high frequency are presented using electrical circuit parameters. Induced overvoltages observed on the secondary side of the transformer are studied in Matlab using three approaches. The transient response in cables based on multiple lengths are studied. The ability to accurately model components allows for an improved understanding of integrating distributed generation in power systems when dealing electromagnetic transients.

Analysis of the thermal-hydraulic parameters of VVER-1200 due to loss of coolant accident concurrent with loss of offsite power

Locating lightning strikes and flashovers along overhead power transmission lines using electromagnetic time reversal

The aim of this paper is to implement different grounding system (GS) models in order to compare its influence on the calculation of overvoltages in transmission lines, produced by direct lightning strikes. The models studied were a lumped DC resistance, a non linear resistance, and a synthesized circuit based on the frequency response of the GS. The latest model is proposed by the authors and takes into account the frequency dependent transient behavior of the GS.

Lightning is a natural phenomenon that can cause serious damages in power systems including wind farms. Wind Turbines (WTs) are tall structures and are often installed in areas with high lightning activity levels which makes them exposed to direct strike. One of the parameters affecting the lightning performance is the impedance of lightning channel. In this paper the effects of this impedance on the induced overvoltage in wind turbines is investigated. The case study is carried out on a WT with 2 MVA of rated power where direct lightning strike with maximum current magnitude of 50kA is struck to the WT. The results of different scenarios are compared, and it is shown that as the value of lightning channel impedance gets higher, the overvoltage caused by the corresponding lightning strike, with the same current magnitude, increases too. This shows the importance of the lightning channel impedance's effect on high-voltage studies of WTs, as it can help in selecting proper lightning protection devices.

Terrestrial gamma‐ray flashes (TGFs) and other high‐energy radiation phenomena related to thunderstorms remain incompletely understood since their discovery nearly 30 years ago. Space and ground‐based platforms have provided insights, but limitations exist in temporal resolution, signal‐to‐noise ratios, and proximity to events. This study presents findings from a balloon‐borne gamma‐ray spectrometer flown into a thunderstorm over northern Mississippi on 19 June 2023. The instrument detected three distinct millisecond‐duration TGF events correlated with lightning strikes. Sustained gamma‐ray glows lasting up to 2 minutes were measured and tied to thunderstorm electrostatic fields. Notably, radiation was observed during a direct lightning strike to the payload. This complex 800‐millisecond event reveals insights into radiation from leader propagation and return strokes. These findings from a single balloon flight demonstrate the prevalence of energetic processes within thunderstorms. Finally, the balloon platform offered an exceptional combination of temporal resolution and validation capabilities to advance the understanding of thunderstorm radiation motivating future follow‐up studies.

The electromagnetic fields produced by both direct lightning strikes and nearby lightning are compared with the nuclear electromagnetic pulse (NEMP) from an exoatmospheric burst. Model calculations indicate that, in the frequency range from 104 to near 107 Hz, the Fourier amplitude spectra of the return stroke magnetic fields near ground 1 m from an average lightning strike will exceed that of the NEMP. Nearby first return strokes at a range of about 50 m, if they are severe, produce electric-field spectra near ground which exceed that of the NEMP below about 106 Hz, while the spectra of average nearby first return strokes exceed that of the NEMP below about 3 x 105 Hz. Implications of these results for aircraft in flight are discussed.

This is a report of death due to direct lightning strike that was witnessed, with description of the injuries. The associated clothing and jewelry were examined microscopically for lightning-related findings. For the first time, we report a lightning strike on a victim that led to crater formations in the brass clasp of the basil wood bead necklace, brass teeth, and brass button of the zipper. Blackening, fissuring, and charring of basil wood beads were noted. There was blackening and fusion of cowrie shell teeth, which were in the black thread necklace. The silver necklace chain vaporized and caused deep burns on the nape of neck. A few links of the silver chain necklace were found embedded in the clothing. All this damage provides important insight into the behavior of lightning.