Lightning Overvoltages in Low-Voltage Circuit for Various Lightning Striking Points

Flashover pattern analysis for 275 kV double circuit transmission lines during direct lightning strikes

Direct or indirect lightning strikes have caused reactor trips in nuclear power generating stations. If nuclear power generating stations do not have adequate lightning protection and grounding, such stations may be exposed to greater risk of loss of offsite power, fire, and damage to redundant trains of engineered safeguard equipment. The loss of offsite power is an important initiating event for design basis accidents. I studied the effects of lightning strikes on reactor trips or misoperation of the equipment from January 1984 through September 2000. From this study, I found that most of the lightning strikes operated the overvoltage protection devices for the control rod drive system. In others, the lightning strikes had partially damaged the main/startup transformers, tripped the switchyard breakers or tripped the transmission lines and, by that, affected the availability of the required stable offsite power sources to the nuclear power generating stations. Direct lightning strikes, electrostatic discharges, lightning electromagnetic impulse can disrupt the electrical and electronic equipment used in the reactor protection system and the other safety systems. The use of the integrated protection and microprocessor-based systems in simplified passive advanced light water reactors and the digital systems replacing the existing analog systems may be more vulnerable to a lightning strike. The protection from lightning could include the installation of lightning dissipation arrays, installation of ferrite shields, installation of a secondary shield or the addition of a short time delay on the power supply monitoring card to allow the transients to dissipate. The instruments and computer grounding system may be grounded through a separate radial grounding system that may be connected to the station grounding grid at only one point to avoid circulating currents. Advanced surge protection devices that include gas discharge tubes, Zener diodes for accurate and fast( picoseconds) voltage control, and metal oxide varistors can be used to protect the electrical and electronic safeguard equipment from high voltage transients associated with lightning.

Influence of photovoltaic support on lightning transient under direct lightning strike

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.

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.

Indonesia is located in a tropical region and has a high number of lightning flash density. In 2021, the latest oil tank fire incident in Balongan and Cilacap, Indonesia, caught the attention of lightning engineers. The oil and gas industry in Indonesia, in general, implements international standards related to lightning protection, such as the NFPA and API standards. However, due to the difference between lightning characteristic in tropical and sub-tropical area, the oil tank and refineries in the tropical area are not inherently self-protected againts lightning direct strikes. Oil and gas industries in tropical area requires additional lightning protection to prevent direct lightning strikes on tank wall, breather valve, and automatic tank gauging (ATG). Based on lightning characteristic in general, lightning can melt oil tank, causing the tank to leak. The voltage difference between the tank wall and the floating roof can cause sparks, then leads to the occurrence of fire. This paper discusses the potential of lightning strike that causes fire tank, including the existance of international standard in tropical area, and the solution of lightning threat, based on captured lightning data.

The great difficulty of encompassing all observed features of ball lightning into a single theory makes it highly probable that many observations and experiences which have no connection to ball lightning are also categorized as ball lightning experiences. In this note we compare the eyewitness reports of ball lightning and the symptoms of epileptic seizures of the occipital lobe as described in the medical literature and show that a person experiencing such a seizure for the first time may believe that he has witnessed a ball lightning event. Since many of the ball lightning reports are associated with nearby lightning strikes, the possibility that the rapidly changing magnetic field of a close lightning strike could trigger an epileptic seizure is analyzed. The results show that the time derivative of the magnetic field in the vicinity of an intense lightning flash is strong enough to stimulate neurons in the brain. This strengthens the possibility of inducing seizures in the occipital lobe of a person located in the vicinity of lightning strikes.

A protocol for selecting viable transmission line arrester for optimal lightning protection

This article presents an investigation on the performance of a three-phase compact distribution line against nearby lightning strikes. It is shown that neglecting the insulating layer that surrounds the phase conductors as usually done in this type of study does not significantly change voltages induced from phase to ground, but can have some effect on voltages induced between phase and messenger, which are the ones that effectively stress the insulation. However, the observed differences are strongly minimized if the usual practice of grounding messenger and neutral in regular intervals of less than 200 m is considered. This is confirmed by a Monte-Carlo-type study that shows that the failure rate of the line is not affected by the inclusion of the insulating layer that surrounds the phase conductors in practical conditions.

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.

For distribution lines in Japan, protection measures against lightning induced overvoltages have been taken and can be considered almost complete. The focus of lightning protection measures has moved to overvoltages due to direct lightning strokes. Studies of such overvoltages require simulations using the EMTP (Electro-Magnetic Transients Program), and components of a distribution line must be modeled appropriately in the EMTP simulation environment. The authors have proposed an EMTP model of a distribution line in a separate paper.This paper consists of two parts. The first part presents surge characteristics of a distribution line obtained by measurement using an actual-scale test distribution line. Especially, the result reveals noteworthy characteristics of the surge impedance of a reinforced concrete pole and the wavefront-time dependence of insulator voltages. The second part presents validation of the distribution line model previously proposed by the authors. The validation shows that the distribution line model accurately reproduces the measured voltage and current waveforms for various wavefront times of injected currents.

The protection of tall structures against direct lightning strikes is usually provided by the installation of a lightning rod of the determined height on the top of the structure. The tip of the rod instead of the top of the structure becomes the point of the initiation of the upward lightning or intercepts the downward lightning. The installed lightning rod does not decrease, even slightly increases the number of lightning incidents to the protected structure. However, there is another alternative lightning protected system, which is being installed instead of the lightning rod, reduces significantly the number of lightning strikes to the structure. This system consists typically of a hemisphere of a large radius with an array of many thin metal splines with sharpened tips distributed evenly over the hemisphere's surface (LPAS). Such LPAS is usually installed on the top of the structure to be protected.

<div class="htmlview paragraph">An investigation of the effects of severe in-flight weather environments on composite structures has been conducted as part of the NASA-Langley Research Center Storm Hazards Program. The on-going program uses an extensively-instrumented F-106B airplane to make thurderstorm penetrations. The vertical fin cap was chosen for the experimental composite structure because of the likelihood of lightning strike attachments and the ease of component replacement. Three components were flown and investigated. The first was the U.S. Air Force production glass/epoxy fin cap which was flame-sprayed by NASA with aluminum for lightning protection. The second fin cap was fabricated with Kevlar/epoxy fabric skins and used an aluminized glass cloth for lightning protection. The third fin cap was fabricated with graphite/epoxy fabric skins with no lightning protection. All three components were exposed to high rain rates and direct lightning strikes. The effects of the flight environments on the components were monitored visually and areas of interest photographed. The performance of the three fin caps and any required repairs are reported herein.</div>

This study simulates lightning strikes and a wind farm using the simulation tool EMTP-RV and analyses the effects of lightning overvoltage. It compares the lightning overvoltage for two grounding methods of lightning arresters-common ground and connected ground. For the simulations, the ground impedance of the lightning arrester is selected according to the earth resistivity and lightning frequency. The study also analyses the resulting magnitude of the overvoltage when corona is the lightning strikes. Thereby, it suggests a method of reducing the lightning overvoltage through various simulations, depicting various conditions such as the change of ground impedance and the grounding method of the lightning arrester.

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.