High Ground Flash Density Research Articles

The Impact of Direct Lightning Strike Damages on PV Modules in a Large Malaysian PV Farm

Many lightning risk analyses avoided considering the role of the PV Module’s aluminium frame as a natural lightning air termination system or if such a role is considered, assumed that the ‘thin’ aluminium frame, would not be damaged from metal melting and evaporation at the point of lightning stroke attachment. Although the IEC 62305 is not lacking in guidance on the use of thin metal sheets as air terminations, this aspect is not considered in PV farm design. To ensure correct inputs into the risk assessment calculation, the evaluation of interception and sizing efficiencies and the damage probabilities of the natural components have to be addressed. A comparative analysis is done between two types of air terminations; the PV-frame LPS and the finial-added LPS. The result indicates that for solar PV farms exceeding a certain size and operating in high ground flash density regions like Malaysia, the finial air termination may out-perform the PV-frame LPS.

Monte‐Carlo‐based simulation and investigation of 230 kV transmission lines outage due to lightning

Here, using the probabilistic evaluation based on the Monte Carlo method, back-flashover rate and shielding failure flashover rate of 230 kV overhead transmission lines in the western regions of Iran are evaluated. To such an aim, first, the number of thunderstorm days per year is collected from the reported weather information in order to determine the ground flash density. Then, using MRU-200 equipment, the tower-footing resistance of several towers is measured. Matlab® software is used in order to produce lightning surges considering its probabilistic nature and randomly distribution on the ground to evaluate striking distance based on the geometric model. Then, calculated parameters are transferred to EMTP-RV software by establishing a link to perform the transient simulation and report the results for modelled 230 kV transmission line. Finally, considering IEEE-1243 standard, it is shown that due to high ground flash density, using 230 kV tower with one shield wire is not sufficient to protect the line against lightning phenomena.

Voltage transient measurements in a distribution network correlated with data from lightning location system and from sequence of events recorders

Measurement units of high-frequency voltage transients have been specifically developed and installed at three different busses of an Italian medium voltage (MV) feeder, mainly composed by overhead lines and located in a rural region characterized by a high ground flash density (4flashes/km2/yr). Several of the recorded voltage transients in the period from March 2007 to August 2008 are correlated with specific events detected by the Italian lightning location system (LLS) CESI-SIRF and with sequence of protection operations recorded by the utility's data acquisition system. The paper presents the analysis of these correlated events. Moreover, the paper compares some voltage transient measurements with the computer simulation results obtained by a detailed LIOV–EMTP model of the MV feeder response to indirect lightning strokes. The aim of the paper is to provide elements useful to solve the problem of correlating line faults with lightning events.

Observations of High Ground Flash Densities of Positive Lightning in Summertime Thunderstorms

Abstract Observations of summertime thunderstorms indicate that positive polarity cloud-to-ground lightning activity can occur with rates as high as 67 flashes in 5 min and spatial densities up to 0.60 flashes per square kilometer per hour. All ground flashes in a storm may be positive for substantial periods. Using data from a nationwide network of magnetic direction finders, 24 storms with high ground flash densities of positive lightning were found on 11 days in June and July 1989 in the Great Plains of the United States. The periods of high-density positive lightning persisted an average of 4 h, longer than the lifetime of a typical single thunderstorm cell. In most cases, they occurred at or near the beginning of the storms' cloud-to-ground lightning activity. Supporting data suggest that the production of high rate and high percentage of positive ground flashes may be associated with exceptionally tall storms that exhibit a stage of early, rapid increase in radar echo-top height and product large hail.

The Use of Network Lightning Data to Detect Thunderstorms near Surface Reporting Stations

Abstract Relationships between network lightning data and hourly thunderstorm observations were examined for the northeastern United States, Oklahoma, Florida, and the western United States to provide additional information on the possible effects of using lightning data to replace or supplement the hourly observations. Identification of thunderstorms for three of the four regions was found to agree closely with the hourly observations, provided the network reports were accumulated for a radius of 48 km or more about the station. The best agreement was found over Florida where high ground-flash densities resulted in a greater likelihood of both observer and network recording a given thunderstorm, In the immediate vicinity (8 km) of a station, use of lightning data from current national or regional networks would not provide observations comparable to the manual observations of thunderstorms due to the poor agreement between the two sets of observations at this radius. Selection of an 8-km radius would res...