This thesis is a case study of a 230 kV transmission line in Lao P.D.R. Grounding of electrical systems is essential for safety and reliability of the system. Several standards are developed for designing a grounding system when building new facilities but it is harder to find references when it is an expansion of an old system or when the area for grounding is inferior. The transmission line is routed over a high resistive limestone ridge, where the requirements from the design standard can not be fulfilled. During normal conditions, each tower can be properly grounded to earth with ground electrodes, but in this case the resistivity of the solid rock is too high. By studying different shield wires of different materials and improve the down lead conductor in each side of the mountain, a suitable solution can be found. The importance of grounding, general description of grounding techniques and the risks for human and equipment due to an electrical fault is also presented in this thesis.

Sprites, halos, and elves are members of a family of short-lived, luminous phenomena known as Transient Luminous Events (TLEs), which occur in the middle atmosphere. Sprites are vertical glows occurring at altitudes typically ranging from ~40 to 90 km. In video imagery they exhibit a red color at their top, with blue tendril-like structure at low altitudes. Elves are disk-like glows that occur at the base of the ionosphere, with diameters of ~100-300 km, and have very short lifetimes (~2-3 ms). Halos are diffuse glows that occur at low altitudes, have diameters <100 km, and have a duration that may last up to 10s of ms. A majority of the studies of TLEs have taken place over the Midwestern U.S. where they were first discovered. This area produces large thunderstorms, which in turn generate large lightning discharges that have been associated with the formation of TLEs. Studies have used the low frequency radiation that initiates with these strokes to study characteristics of these events. This low frequency radiation has been used to determine where large numbers of TLEs may occur. Extreme southern Brazil is a region of the globe believed to have many TLEs, but few studies on these phenomena. Two collaborative campaigns involving Utah State University proceeded in 2002-2003, and in 2006. Multiple TLE images were made, proving this is, indeed, a region of the globe where these types of events are prominent. In particular, one storm in February 2003 produced over 440 TLEs imaged by USU video cameras. Of these events, over 100 of them had associated halos. Statistical studies for halos previously had been performed in the U.S., but never abroad. Also, several events from the February storm have been associated with negative cloud to ground lightning, a surprising occurrence, as to date, less than a handful of such events have ever been witnessed or published. In analyzing the TLEs from this campaign, we have shown the halos are similar to those seen in the U.S., even though the storms may be somewhat different. Also, detailed analyses of the negative events show both temporal and spatial morphology heretofore never reported on.

In this study, it is hypothesized that the mesoscale environment can indirectly control the cloud-to-ground (CG) lightning polarity of severe storms by directly affecting their structural, dynamical, and microphysical properties, which in turn directly control cloud electrification and CG flash polarity. A more specific hypothesis, which has been supported by past observational and laboratory charging studies, suggests that broad, strong updrafts and associated large liquid water contents in severe storms lead to enhanced positive charging of graupel and hail via the noninductive charging mechanism, the generation of an inverted charge structure, and increased positive CG lightning production. The corollary is that environmental conditions favoring these kinematic and microphysical characteristics should support severe storms generating an anomalously high (> 25%) percentage of positive CG lightning (i.e., positive storms), while environmental conditions relatively less favorable should sustain storms characterized by a typical (≤ 25%) percentage of positive CG lightning (i.e., negative storms). Forty-eight inflow proximity soundings were analyzed to characterize the environments of nine distinct mesoscale regions of severe storms (four positive and five negative) on six days during May – June 2002 over the central United States. This analysis clearly demonstrated significant and systematic differences in the mesoscale environments of positive and negative storms, which were consistent with the stated hypothesis. When compared to negative storms, positive storms occurred in environments associated with a drier low to midtroposphere, higher cloud base height, smaller warm cloud depth, stronger conditional instability, larger 0-3 km AGL wind shear, stronger 0-2 km AGL storm-relative wind speed, and larger buoyancy in the mixed-phase zone, at a statistically significant level. Differences in the warm cloud depth of positive and negative storms were by far the most dramatic, suggesting an important role for this parameter in controlling CG lightning polarity. Subjective visual inspection of radar imagery revealed no strong relationship between convective mode and CG lightning polarity, and also illustrated that positive and negative severe storms can be equally intense.

Starting with a group of lightning researchers, planetarium staff, and visualization specialists, an academically diverse group was formed through a grant from the National Science Foundation to develop a planetarium show on lightning. The show target audience is middle school aged children. The goal of the show is to teach lightning safety and lightning facts in an immersive environment. Through the use of video, an animated character, and a meteorologist, the curriculum is presented to the audience. I fulfilled the roles of producer and director through all aspects of production. My role also included maintaining group organization and communication throughout show production. This paper discusses my experiences in producing Enlightening Lightning! by starting with outlining the curriculum and finishing with putting it all together at the planetarium. The goal of this paper is to discuss the techniques and organizational methods used to manage a diverse group and produce a multimedia show.

In this study, it is hypothesized that the mesoscale environment can indirectly control the cloud-to-ground (CG) lightning polarity of severe storms by directly affecting their structural, dynamical, and microphysical properties, which in turn directly control cloud electrification and CG flash polarity. A more specific hypothesis, which has been supported by past observational and laboratory charging studies, suggests that broad, strong updrafts and associated large liquid water contents in severe storms lead to enhanced positive charging of graupel and hail via the noninductive charging mechanism, the generation of an inverted charge structure, and increased positive CG lightning production. The corollary is that environmental conditions favoring these kinematic and microphysical characteristics should support severe storms generating an anomalously high (> 25%) percentage of positive CG lightning (i.e., positive storms), while environmental conditions relatively less favorable should sustain storms characterized by a typical (≤ 25%) percentage of positive CG lightning (i.e., negative storms). Forty-eight inflow proximity soundings were analyzed to characterize the environments of nine distinct mesoscale regions of severe storms (four positive and five negative) on six days during May - June 2002 over the central United States. This analysis clearly demonstrated significant and systematic differences in the mesoscale environments of positive and negative storms, which were consistent with the stated hypothesis. When compared to negative storms, positive storms occurred in environments associated with a drier low to midtroposphere, higher cloud base height, smaller warm cloud depth, stronger conditional instability, larger 0-3 km AGL wind shear, stronger 0-2 km AGL storm-relative wind speed, and larger buoyancy in the mixed-phase zone, at a statistically significant level. Differences in the warm cloud depth of positive and negative storms were by far the most dramatic, suggesting an important role for this parameter in controlling CG lightning polarity. Subjective visual inspection of radar imagery revealed no strong relationship between convective mode and CG lightning polarity, and also illustrated that positive and negative severe storms can be equally intense.

A comparison of flash parameters from the National Lightning Detection Network (NLDN) is made with data obtained from the Houston Lightning Detection and Ranging II (LDAR) network. This research focuses on relating the peak current and number of strokes in a negative flash (multiplicity) of lightning with the spatial extent and mean altitude of three-dimensional lightning in 1407 flashes as mapped by the LDAR network. It is shown that increasing negative multiplicities over the range two through ten exhibit, on average, a higher flash extent with higher multiplicities. Singlestroke flashes have mean heights of nearly 2 km greater. Higher order multiplicities (2 to 10+) were correlated with mean source heights near 8 km. Increasing multiplicity tends to be associated with greater flash extents increasing more horizontally than vertically with a 50% to 70% increase in flash extent. No obvious relationship between peak current and flash extent was observed. Examining peak current and mean height shows that low current flashes (<10kA) exhibit higher mean heights. However, this may be due to intra-cloud only flashes being reported as cloud to ground events by the NLDN. Bipolar flashes do not show much variation with height and flash extent with the exception of negative-first bipolar flashes, which exhibited mean flash extents twice that of other types. Finally, the flash detection efficiency is 99.7% within 60 km of the network center.

Most of the working population in Ghana are farmers. It is of importance for them to know where and when precipitation will occur to prevent crop losses due to droughts and floodings. In order to have a sustainable agriculture, improved rainfall forecasts are needed. One way to do that is to enhance the initial conditions for the rainfall models. In the mid-latitudes, in-situ rainfall observations and radar data are used to monitor weather and measure rainfall. However, due to the lack of station data and the present absence of a radar network in West Africa, other rainfall estimates are needed as substitutes. The rainfall amount in convective systems, dominating in West Africa, is coupled to their vertical structure. Therefore, satellite measurements of cloud top temperatures and microwave scatter, as well as the number of lightning, can be used to estimate the amount of rainfall. In this report, derived rainfall estimates from satellites and the use of lightning data are analysed to see how well they estimate the actual rainfall amount. The satellite datasets used in this report are NOAA RFE2.0, NOAA ARC2, and the EUMETSAT MPE. The datasets were compared to in-situ measurements from GTS- and NGO collaborating observation stations in order to verify which satellite dataset that best estimates the rainfall or, alternatively, if a combination between two or all the datasets is a better approach. Lightning data from Vaisala GLD360 have been compared to GTS-station data and RFE2.0 to see if a relation between the number of lightning and rainfall amount could be found. It was also tested whether a combination between the satellite- and lightning data could be a better estimate than the two approaches separately. Rainfall estimates from RFE2.0 alone showed the best correlation to GTS- and the NGO collaborating station data. However, a difference in how well RFE2.0 estimated rainfall at GTS-stations compared to reference stations was seen. Comparing RFE2.0 to GTS-stations showed a better correlation, probably due to the use of these observations in the build up of RFE2.0. Even though RFE2.0 showed the best correlation compared to other datasets, satellite estimates showed in general poor skill in catching the actual rainfall amount, strongly underestimating heavy rainfall and somewhat overestimating lighter rainfall. This is probably due to the rather basic assumptions that the cloud top temperature is directly coupled to rain rate and also the poor temporal resolution of the polar orbiting satellites (carrying microwave sensors). Better instruments and algorithms need to be developed to be able to use satellite datasets as an alternative to rainfall measurements in West Africa. Furthermore, due to the lack of station data, only tentative results between GLD360 and GTS-stations could be made, showing a regime dependence. When further analysed to RFE2.0, a stronger temporal dependence, i.e. seasonal variation, rather than a spatial one was seen, especially during the build up of the monsoon. However, due to poor rainfall estimates from RFE2.0, no accurate rainfall-lightning relation could be made but trends regarding the relation were seen. The use of GLD360 showed to be an effective way to erase false precipitation from satellite estimates as well as locating the trajectory of convective cells. To be able to further analyse rainfall/lightning relation, more measurements of the true rainfall is needed from e.g. a radar. / Majoriteten av Ghanas befolkning arbetar inom jordbrukssektorn. Det är viktigt för jordbrukarna att veta när och var nederbörd kommer att falla för att deras skörd inte ska bli förstörd av till exempel torka eller översvämningar. Det behövs därför bättre nederbördsprognoser för ett hållbart jordbruk. Ett sätt att få mer noggranna prognoser är att förbättra initialvärden till nederbördsmodellerna. Vid de mellersta breddgraderna på norra halvklotet används nederbördsmätningar från in-situ stationer samt data från radarsystem som initialvärden, men på grund av få mätstationer och inget radarsystem i västra Afrika behövs alternativa nederbördsestimater. Nederbörden i västra Afrika domineras av konvektiva system, vars regnmängd är kopplad till dess vertikala struktur. Satellitmätningar av molntoppstemperaturen och mikrovågornas spridning och absorption, liksom antalet blixtar är också relaterat till molnets struktur och kan därför användas för att estimera nederbördsmängden. I den här rapporten analyserades nederbördsestimater från satellitdata samt användning av blixtdata för att undersöka hur bra metoderna är på att estimera den verkliga nederbördsmängden. Satellitdataseten som analyserades var NOAA RFE2.0, NOAA ARC2 och EUMETSAT MPE. Dataseten jämfördes med in-situ mätningar från GTS-stationer samt observationerfrån NGO-samarbetande jordbrukare för att verifiera vilket satellitdataset som ger det bästa nederbördsestimatet, alternativt att en kombination mellan två eller alla dataset ger det bästa estimatet. Vidare har blixtdata från Vaisala GLD360 jämförts med GTS-stationer och RFE2.0 för att se om antalet blixtar är relaterat till nederbördsmängden. Slutligen har det också undersökts om en kombination mellan satellit- och blixtdata är ett bättre än de två metoderna separat. Nederbördsestimater från RFE2.0 visade på bäst korrelation med både GTS- och NGO-stationer. En tydlig skillnad noterades dock i RFE2.0:s förmåga att estimera nederbörd vid jämförelse mellan de två stationsdataseten. En bättre korrelation mellan RFE2.0 och GTS-stationerna påvisades, troligen för att RFE2.0 använder dessa observationer i uppbyggnaden av datasetet. Även om RFE2.0 visade på bäst korrelation i jämförelse med ARC2 och MPE var samtliga satellitdataset dåliga på att estimera den verkliga nederbördsmängden. De underestimerar starkt stora mängder nederbörd samtidigt som de överestimerar små mängder. Anledningen är troligen det relativt enkla antagandet att molntoppstemperaturen är direkt kopplad till molnets regnmängd samt den dåliga tidsupplösningen på de polära satelliterna som är utrustade med mikrovågssensorer. För att satellitdataseten ska kunna användas som ett alternativt nederbördsestimat i Västafrika behövs bättre mätinstrument och algoritmer. Vid analysen mellan GLD360 och GTS-stationer kunde, på grund av för få stationsdata, endast övergripande resultat erhållas. Ett områdesberoende gick dock att urskilja som vid en ytterligare analys mellan GLD360 och RFE2.0 visade på ett större säsongsberoende, särskilt under uppbyggnaden av monsunperioden i april och maj. Eftersom RFE2.0 visade sig ha dåliga nederbördsestimat kunde ingen noggrann koppling hittas, utan resultatet visade på trender samt möjligheter att kunna använda blixtdata som ett alternativt nederbördsestimat. Till exempel visade det sig att GLD360 kunde användas som ett verktyg för att sålla bort falsk nederbörd från satellitestimat samt identifiera trajektorien för ett konvektivt system. För en djupare analys i att relatera blixtar och nederbörd i Västafrika krävs bättre tekniker för att estimera nederbörd eller fler in-situ observationer.

Η παρούσα διπλωματική εργασία ασχολείται με τον έλεγχο και τη μέτρηση των γειώσεων από τα συστήματα αντικεραυνικής προστασίας των κτιρίων του Πανεπιστημίου Πατρών. Σκοπός του συστήματος γείωσης είναι να υλοποιεί την απαγωγή και διάχυση του ρεύματος από τον κεραυνό μέσα στη γη, χωρίς να δημιουργούνται επικίνδυνες υπερτάσεις που μπορεί να πλήξουν τον άνθρωπο ή τον εξοπλισμό. Στο πρώτο κεφάλαιο γίνεται περιγραφή βασικών εννοιών σχετικά με τα ηλεκτρικά φαινόμενα που εμφανίζονται στην ατμόσφαιρα. Συγκεκριμένα αναλύεται πως δημιουργούνται οι κεραυνοί και ποια είναι τα είδη τους, η συχνότητα των κεραυνικών πληγμάτων, οι συνέπειές τους και η αρχή λειτουργίας των αλεξικεραύνων. Στο δεύτερο κεφάλαιο περιγράφονται βασικές έννοιες για το σύστημα αντικεραυνικής προστασίας, πως γίνεται η σχεδίασή του, τα υλικά που απαιτούνται και πως καθορίζεται η στάθμη προστασίας για την εκάστοτε κατασκευή και τον εκάστοτε τόπο. Στο τρίτο κεφάλαιο περιγράφονται οι συνθήκες και η επίδρασή τους στο αποτέλεσμα των μετρήσεων όπως οι καιρικές συνθήκες και οι διάφοροι μέθοδοι μέτρησης των γειώσεων. Τέλος παρουσιάζονται οι μετρήσεις των γειώσεων από όλα τα κτίρια του Πανεπιστημίου Πατρών. Ακολουθούν τα συμπεράσματα αυτής της μελέτης και το παράρτημα με τις εικόνες που επισημαίνουν διάφορα σημεία του Πανεπιστημίου Πατρών. Τέλος παρουσιάζεται η βιβλιογραφική αναφορά των πηγών για αυτή την εργασία. / The subject of this study deals with the control and measurement of earthing systems of lightning protection of buildings in the University of Patras. The purpose of the grounding system is to implement the kidnapping and diffusion current from the lightning into the earth without creating dangerous power surges that can harm humans or equipment. The first chapter is a description of basic concepts relating to electrical phenomena that occur in the atmosphere. It is analyzed that generated lightning and what are their types, the frequency of lightning strikes, their consequences and the operating principle of lightning conductors. The second chapter describes basic concepts for the lightning protection system, the way that this system can be designed, the materials needed and how the level of protection can be determined for each building and each site. The third chapter presents the conditions and their effect on outcome measurements such as weather conditions and the various methods of earthing measurement. Finally measurements of the ground are presented from all the buildings in the University of Patras. Following the conclusions of this study, is included the appendix with images that highlight various points. At the end, is the bibliographic reference sources for this work.

Thunderstorms that occur in areas of complex terrain are a major severe weather hazard in the intermountain western U.S. Short-term quantitative estimation (QPE) of precipitation in complex terrain is a pressing need to better forecast flash flooding. Currently available techniques for QPE, that utilize a combination of rain gauge and weather radar information, may underestimate precipitation in areas where gauges do not exist or there is radar beam blockage. These are typically very mountainous and remote areas, that are quite vulnerable to flash flooding because of the steep topography. Lightning has been one of the novel ways suggested by the scientific community as an alternative to estimate precipitation over regions that experience convective precipitation, especially those continental areas with complex topography where the precipitation sensor measurements are scarce. This dissertation investigates the relationship between cloud-to-ground lightning and precipitation associated with convection with the purpose of estimating precipitation- mainly over areas of complex terrain which have precipitation sensor coverage problems (e.g. Southern Arizona).The results of this research are presented in two papers. The first, entitled Toward Development of Improved QPE in Complex Terrain Using Cloud-to-Ground Lighting Data: A case Study for the 2005 Monsoon in Southern Arizona, was published in the Journal of Hydrometeorology in December 2012. This initial study explores the relationship between cloud-to-ground lightning occurrences and multi-sensor gridded precipitation over southern Arizona. QPE is performed using a least squares approach for several time resolutions (seasonal -June, July and August-, 24 hourly and hourly) and for a 8 km grid size. The paper also presents problems that arise when the time resolution is increased, such as the spatial misplacing of discrete lightning events with gridded precipitation and the need to define a "diurnal day" that is synchronized with the diurnal cycle of convection. The second manuscript (unpublished), entitled An Improved QPE Over Complex Terrain by Using Cloud-to-Ground Lightning Occurrences, provides a new method to retrieve lightning-derived precipitation at 5 minutes and 5 Km time and space resolutions. A stationary model that employs spatio-temporal neighboring (Space and Time Invariant model -STI) improves upon the least squares method in the first paper. By applying a Kalman filter to the STI model, lightning-precipitation is retrieved by a dynamic model that changes in time. The results for seasonal and 5 minutes time resolution show that the dynamic model improves the retrievals derived by the STI model.

Στις μέρες μας λόγω της εξάντλησης των αποθεμάτων πετρελαίου, έχουμε στραφεί σε άλλες μορφές παραγωγής ηλεκτρικής ενέργειας, μία από τις οποιές είναι η παραγωγή ηλεκτρικής ενέργειας μέσω φωτοβολταϊκών συστημάτων. Η ηλιακή ακτινοβολία μετατρέπεται απευθείας σε ηλεκτρική με την βοήθεια ημιαγωγικών στοιχείων χωρίς να επιβαρύνει το περιβάλλον. Το φαινόμενο της απευθείας μετατροπής της ηλιακής ενέργειας σε ηλεκτρική, ονομάστηκε φωτοβολταϊκό φαινόμενο. Με την πάροδο του χρόνου το κόστος των φωτοβολταϊκών συστημάτων όλο και μειώνεται γι΄αυτο και περισσότερα φωτοβολταϊκα συστήματα προτιμώνται έναντι των συμβατικών μορφών ενέργειας. Στο πρώτο κεφάλαιο αυτής της διπλωματικής θα αναφερθούν γενικά στοιχεία των φωτοβολταϊκών συστημάτων. Υπάρχουν δύο διαφορετικές κατηγορίες φωτοβολταϊκών συστημάτων, τα διασυνδεδεμένα στο δίκτυο φωτοβολταϊκά συστήματα και τα αυτόνομα φωτοβολταϊκά συστήματα. Τα διασυνδεδεμένα φωτοβολταϊκά συστήματα αποτελούνται από τα φωτοβολταϊκά πλαίσια, τον πίνακα ελέγχου, τον αντιστροφέα τάσης και τον μετρητή της Δ.Ε.Η. Τα αυτόνομα φωτοβολταϊκά συστήματα αποτελούνται από τα φωτοβολταϊκά πλαίσια, τον πίνακα ελέγχου, τον ρυθμιστή φόρτισης, τον συσσωρευτή (μπαταρία) και τον αντιστροφέα τάσης. Στο δεύτερο κεφάλαιο αυτής της διπλωματικής θα γίνει ανάλυση όλων των κύριων τμημάτων που απαρτίζουν ένα φωτοβολταϊκό σύστημα διασυνδεδεμένο ή αυτόνομο. Για να έχουμε μεγάλη διάρκεια ζωής σε ένα φωτοβολταϊκό σύστημα είναι απαραίτητη μια αποτελεσματική αντικεραυνική προστασία και μια καλή προστασία υπέρτασης. Η ανάλυση των μεθόδων αντικεραυνικής προστασίας και των μεθόδων προστασίας υπέρτασης είναι το αντικείμενο του τρίτου κεφαλαίου. Ενα κεραυνικό πλήγμα στα φωτοβολταϊκά συστήματα μπορεί να προκαλέσει σοβαρές ζημιές στα πλαίσια και τους αντιστροφείς, καθώς και μεγάλες οικονομικές απώλειες (αντικατάσταση του εξοπλισμού, απώλεια παραγωγής κ.τ.λ) που το κόστος εγκατάστασης ενός πλήρους συστήματος αντικεραυνικής προστασίας συμφέρει οικονομικά. / In our days because the exhaustion of reserves of oil, we have been turned in other forms of production of electric energy, one from that are the production of electric energy via photovoltaic systems. The solar radiation is changed directly in electric with the help of semiconductor elements without it overloads the environment. The phenomenon of direct transformation of solar energy in electric, was named photovoltaic phenomenon. With the byway of time the cost of photovoltaic systems is always decreased photovoltaic systems is preferred against the conventional forms of energy. In the first chapter this diplomatic will be reported in general elements of photovoltaic systems. Exist two different categories of photovoltaic systems, Connected in the electric grid photovoltaic systems and the stand alone photovoltaic systems. The stand alone photovoltaic systems are constituted by the photovoltaic frames, the table of control, inverter. The photovoltaic systems are autonomously constituted by the photovoltaic frames, the table of control, the regulator charge, the accumulator (battery) and inverter . In the second chapter this diplomatic will become analysis of all main departments that composes a photovoltaic system connected to the grid or stand alone. In order to we have big duration of life in a photovoltaic system are essential a effective lightning protection and a good protection of overvoltage. The analysis of methods of lightning protection and methods of protection of overvoltage is the object of third chapter. A lightning strike in the photovoltaic systems can cause serious damage in the frames and inverter, as well as big economic losses (replacement of equipment, loss of production ) that the cost of installation of complete system of lightning protection is advance economically.