Η παρούσα διπλωματική εργασία καταπιάνεται με τη μελέτη της συμπεριφοράς των φωτοβολταϊκών πλαισίων σε καταπόνηση με κρουστικές τάσεις κεραυνών. Πιο συγκεκριμένα, εφαρμόστηκαν σε ένα φωτοβολταϊκό πλαίσιο κρουστικές τάσεις, συμφωνά με τον κανονισμό IEC 61730-2,και μετρήθηκε το αν και κατά πόσο επηρεάστηκε η λειτουργία του πλαισίου. Το πρώτο κεφάλαιο παρέχει το θεωρητικό πλαίσιο της έρευνας. Αναλυτικότερα, παρέχεται η αρχή λειτουργίας του μονοκρυσταλλικού πλαισίου, και αναφέρονται τα τεχνικά χαρακτηριστικά αυτού που χρησιμοποιήσαμε στην παρούσα εργασία. Παρατίθεται η αρχή λειτουργίας της κρουστικής γεννήτριας που χρησιμοποιήθηκε στο πειραματικό σκέλος και δίνεται ο ορισμός της κρουστικής τάσης. Τέλος, δίνονται πληροφορίες ως προς τη μετρητική συσκευή που χρησιμοποιήθηκε για τη μελέτη της καλής λειτουργίας του πλαισίου. Το δεύτερο κεφάλαιο σχετίζεται με το πειραματικό κομμάτι της έρευνας. Πιο συγκεκριμένα, παρατίθενται οι κρουστικές τάσεις που έπληξαν το πλαίσιο και γίνεται εκτενής και σαφής αναφορά στον κανονισμό IEC 61730-2 που υπαγορεύει τους κανόνες διεξαγωγής του πειράματος. Τέλος, παρουσιάζονται οι ακριβείς συνθήκες διεξαγωγής της πειραματικής διαδικασίας ενώ περιέχονται φωτογραφίες που πάρθηκαν κατά τη διάρκεια υλοποίησης της έρευνας. Στο τρίτο κεφάλαιο καταγράφονται τα αποτελέσματα των μετρήσεων καλής λειτουργίας του φωτοβολταϊκού πλαισίου και παρουσιάζονται σε πίνακες και χαρακτηριστικές I-V. Αποτελέσματα που πάρθηκαν τόσο πριν όσο και μετά από κάθε καταπόνηση. Κλείνοντας, στο τέταρτο και τελευταίο κεφαλαίο, εξάγονται συμπεράσματα και γίνεται εκτενής ανάλυση των αποτελεσμάτων που καταγράφηκαν στο κεφάλαιο 3. Τα τελικά συμπεράσματα σχετίζονται με το αν επηρεάστηκε ή όχι η καλή λειτουργία του κυττάρου. Ακόμα, παρουσιάζονται κάποιες αδυναμίες της έρευνας μας καθώς και κάποια ερωτήματα-προτάσεις περεταίρω διευρένησης, που μας γεννήθηκαν κατά την ενασχόλησή μας με το θέμα. / This thesis deals with the study of the behavior of the modules when applying lightning impulse voltages. In particular, percussive tendencies were applied to a solar cell, according to the regulation IEC 61730-2, and it was measured whether and how the functioning of the framework was affected. The first chapter provides the theoretical framework of the research. More specific, it is given the operating principle of the single crystal framework and there are referred the technical features which were used in this work. It is presented the operating principle of the impulse generator used in the experimental arm and it is given the definition of “voltage impulse”. Finally, there are presented information on the measuring device used to the study of the proper functioning of the framework. The second chapter is related to the experimental part of the investigation. To be more specified, there are given the percussive tendencies that affected cell and a detailed and clear reference to IEC 61730-2 regulation that dictates the rules of our experiments. Finally, we present the precise conditions under which the experimental procedure was done and there are contained photographs which were took during the implementation of the survey. In the third chapter, they are displayed the results of the measurements proper operation of photovoltaic panel and they are presented in tables and characteristic IV. The results were obtained both before and after each exposure Finally, in the fourth and final chapter, conclusions are drawn and there is a detailed analysis of the results recorded in chapter 3. The final conclusions relating to whether or not the proper cell function was affected . In conclusion, they are presented some shortcomings in our research and some questions (further recommendations for research), there were entered to our minds during our involvement with the issue.

Η ευρεία χρήση του ηλεκτρισμού και η συνεχής αύξηση των μεγεθών μεταφοράς και διανομής της υψηλής τάσης αναγκάζει τον επιστημονικό κόσμο να επενδύσει στην κατανόηση της συμπεριφοράς των ατμοσφαιρικών υπερτάσεων δηλαδή των κρουστικών τάσεων κεραυνών, και των εσωτερικών υπερτάσεων όπως των κρουστικών τάσεων χειρισμών όπως και της συμπεριφοράς του εξοπλισμού των υψηλών τάσεων. Είναι αναγκαία επίσης η κατανόηση της αλληλεπίδρασης των πιο πάνω για σκοπούς βελτίωσης της ασφάλειας και της αξιοπιστίας του εξοπλισμού των υψηλών τάσεων. Στόχος της παρούσας διπλωματικής εργασίας είναι η διερεύνηση του κατά πόσον τα χρονικά χαρακτηριστικά των κρουστικών τάσεων μπορούν να επιδράσουν στη τάση διάσπασης των διακένων αέρα και γενικότερα στην συμπεριφορά τους. Έτσι αναζητείται η τάση διάσπασης του διακένου αέρα τόσο ποσοτικά (μεταβολή στο μέγεθος) όσο και ποιοτικά (μεταβολή των στατιστικών χαρακτηριστικών). Η διπλωματική εργασία τούτη αποτελεί μια συνεισφορά στην διεθνή ερευνητική προσπάθεια που γίνεται πάνω στο αντικείμενο συλλογής πληροφοριών και εξαγωγής συμπερασμάτων για τα διάφορα είδη κρουστικών τάσεων σε συνδυασμό με τα διάκενα αέρα. Αρχικά παρατίθενται μια θεωρητική ανασκόπηση βασιζόμενη στην διεθνή βιβλιογραφία που αφορά τα κυκλώματα παραγωγής κρουστικών τάσεων στο εργαστήριο. Σκοπός τούτου είναι η αποσαφήνιση του τρόπου παραγωγής των κρουστικών τάσεων στο εργαστήριο με πρωτοβάθμιες, δευτεροβάθμιες και πολυβάθμιες κρουστικές γεννήτριες. Επίσης παρουσιάζεται ένα θεωρητικό μοντέλο υπολογισμού των αναμενόμενων κρουστικών τάσεων μιας δευτεροβάθμιας κρουστικής γεννήτριας του οποίου τα αποτελέσματα παρουσιάζονται. Στη συνέχεια παρατίθεται μια θεωρητική ανασκόπηση που αφορά τα διάκενα αέρα, τους μηχανισμούς διάσπασης τους, τον τρόπο ανάλυσης των πειραματικών αποτελεσμάτων και την επίδραση που έχουν στην διάσπαση των διακένων αέρα οι ατμοσφαιρικές συνθήκες. Όλα τα παραπάνω έχουν σκοπό να αποσαφηνίσουν τους παράγοντες που χρήζουν ιδιαίτερης προσοχής ώστε να εξασφαλιστούν τα πλέον αξιόπιστα πειραματικά αποτελέσματα, καθώς και η δημιουργία μιας βάσης θεωρητικών δεδομένων που θα βοηθήσουν στην αξιοποίηση των πειραματικών μετρήσεων. Για την διεξαγωγή της πειραματικής διαδικασίας χρησιμοποιήθηκε η γεννήτρια κρουστικών τάσεων Multi test set της εταιρείας Haefely, κομμάτι του ηλεκτρομηχανικού εξοπλισμού του εργαστηρίου Υψηλών Τάσεων. Με αυτήν την γεννήτρια παρήχθησαν κρουστικές τάσεις τάξης μεγέθους 100 kV και ένα πλήθος τύπων κρουστικών τάσεων ως προς τα χρονικά χαρακτηριστικά ουράς και μετώπου τα οποία παρήχθησαν με συνδυασμό των αντιστάσεων μετώπου R2 με τις αντιστάσεις ουράς R1. Μέσω κατάλληλου κρουστικού βολτομέτρου και με ψηφιακό παλμογράφο έγιναν οι μετρήσεις αυτών των τάσεων και η αποτύπωση των κυματομορφών τους. Τα διάκενα αέρα τα οποία καταπονήθηκαν σε αυτές τις κρουστικές τάσεις είναι: Σφαίρα-Σφαίρα, Ακίδα-Σφαίρα, Ακίδα-Ακίδα. Για τον υπολογισμό της τάσης διάσπασης U50% λήφθησαν για κάθε περίπτωση 3 έως 4 σετ των 30 έως 50 μετρήσεων. Τα συνολικά αποτελέσματα και η διαγραμματική τους απεικόνιση με τις απαραίτητες επ’αυτών παρατηρήσεις, ενσωματώνονται στην εργασία και βασιζόμενη σε αυτά ακολουθεί η απαραίτητη συμπερασματολογία. Το αποτέλεσμα αυτής της εργασίας ήταν η διαπίστωση θεωρητικά και πειραματικά του τρόπου επίδρασης των κατασκευαστικών στοιχείων της γεννήτριας στα χρονικά χαρακτηριστικά των παραγόμενων κρουστικών τάσεων. Επίσης διαπιστώθηκε ότι η προσθήκη των συγκεκριμένων διακένων αέρα έχει σαν αποτέλεσμα μικρή αύξηση των χρονικών χαρακτηριστικών της κρουστικής τάσεως (χρόνου ουράς και μετώπου) τάξεως του 2-3%. Το βασικό συμπέρασμα όμως είναι ότι τα χρονικά χαρακτηριστικά των κρουστικών τάσεων παίζουν καθοριστικό ρόλο στην τάση διάσπασης U50% των διακένων αέρα. Συγκεκριμένα για γρήγορους χρόνους μετώπου η τάση διάσπασης U50% βρίσκεται στο χαμηλό επίπεδο και αυξάνεται απότομα για μεγαλύτερους χρόνους μετώπου Τ1 και αποτελεί την μέγιστη τάση διάσπασης. Στη συνέχεια με την αύξηση των χρόνων μετώπου η τάση διάσπασης U50% μειώνεται. Η επίδραση των χρόνων ουράς είναι ότι καθώς αυξάνονται μειώνουν την τάση διάσπασης U50%. / The worldwide use of electricity and the continuous increase of demand in the distribution of high voltage, has forced the entire scientific community to turn and invest to the study and understanding the behavior of atmospheric surge phenomenon such as thunder, lighting, impulse voltage, and the internal over voltages such as switching voltages. It is considered essential to investigate the response and behavior of the high voltage equipment. The challenging part is to gain the knowledge on how these interact with each other, in order to improve the security and reliability of high voltage machines. The aim of this thesis is to investigate whether the time variant characteristics of the impulse voltages can affect the degradation behavior of air discharge. Our target is to discover the chopping voltage of air gaps in actual number but also to find out the variation of its statistical characteristics. This paper will contribute to the international research effort of collect information and extracting results for the various types of impulse voltage combined with air gaps. Initially we present a theoretical approach based on the international bibliography concerning the circuits that create impulse voltages in a laboratory environment. Our aim is to clarify the way impulse voltages are produced in the laboratory, from singlestage, two-stage and multi-stage impulse generators. Furthermore, we present a theoretical model for calculating the impulse voltage created by a two-stage impulse generator. All these results are also included in our paper. Next, we complete our overview by presenting the air discharge phenomena, analysis methods used to investigate experimental result and the overall effect of atmospheric conditions on air discharge splitting. All these aim to clarify the factors which need to be taken into consideration in order to secure reliable experimental results but also a more complete database of the theoretical data that can be utilised in more advanced experimental methods. In order to complete our experiments we used the Multi test set impulse voltage generator, produced by Haefely Company and is a part of high Voltage laboratory equipment. With the help of this generator we managed to produce a number of impulse voltages of size 100 kV, and various types of impulse voltages using the time variant characteristics connecting together tail and head resistors R2 and R1 respectively. Using a suitable impulse voltage meter and a digital oscilloscope we managed to measure these voltages and create a graphical representation of their waveforms. The air-gaps created from these voltages are: Sphere-Sphere, Spike- Sphere, Spike-Spike. In order to calculate the chopping voltage U50% we collected 3 to 4 set consisted of 30-50 measurements. The overall results and their diagram presentation followed by relevant conclusions are included in this paper. Based on these we were able to draw all necessary conclusions. On this paper we managed to extract theoretically and experimentally how all constructional elements of the generator affect the time variant characteristics of the impulse voltages created. We also concluded that adding specific air gaps will result to a slight increase of the time variant characteristic of the impulse voltage (frontwave and tail-wave duration) by 1%-3%.The main conclusion was that the time variant characteristics of impulse voltages play a decisive role in the chopping voltage U50% of air gaps. More specifically, for short-duration of wave-front T1 the chopping voltage U50% lays on the lower level whereas it automatically increases for bigger duration Τ1 and this is our higher chopping voltage. Then the chopping voltage U50% is reduced by increasing the duration of wave-front T1. Also the increase of wave-tail duration results to a reduction of chopping voltage U50%.

As linhas de distribuição de energia estão freqüentemente expostas a sobretensões causadas por descargas atmosféricas diretas e indiretas. As formas de onda dessas sobretensões têm uma faixa de variação muito ampla e podem diferir bastante do impulso atmosférico normalizado utilizado em ensaios para verificação da adequação dos projetos das isolações dos equipamentos frente a sobretensões atmosféricas (1,2 / 50 microssegundos). É fato conhecido que a suportabilidade das isolações depende não só da amplitude como da forma de onda das solicitações. Diferentes modelos têm sido propostos para se estimar o desempenho das isolações frente a impulsos não normalizados, sendo o modelo do efeito disruptivo (disruptive effect model) um dos mais utilizados. Existem, contudo, diferentes métodos de aplicação desse modelo, ou seja, diferentes formas de se estimar os parâmetros necessários para a sua aplicação. Este trabalho visa avaliar o comportamento dielétrico de isoladores de média tensão e analisar os principais métodos para estimativa da suportabilidade desses equipamentos frente a sobretensões atmosféricas com formas de onda diferentes da normalizada. Para essa avaliação foram realizados ensaios em um isolador tipo pino, de porcelana, com tensão nominal de 15 kV, nos quais foram utilizadas, além do impulso atmosférico normalizado, outras ondas selecionadas com base em resultados de medição e de cálculo. Modificações realizadas no circuito de um gerador de impulsos de alta tensão convencional permitiram a geração de tensões com formas de onda bastante semelhantes às de sobretensões induzidas por descargas atmosféricas tanto em linhas de tamanho natural como em experimentos realizados com modelo reduzido. São apresentados e discutidos os resultados dos ensaios de tensão disruptiva de impulso atmosférico a 50 % e as curvas tensão-tempo (U x t) obtidas para cada impulso, considerando ambas as polaridades. A avaliação dos métodos de aplicação do modelo do efeito disruptivo foi realizada com base em comparações entre as curvas tensão-tempo obtidas nos ensaios e as curvas previstas por cada modelo, para cada uma das ondas selecionadas. / Overhead distribution lines are often exposed to lightning overvoltages, whose waveshapes vary widely and can differ substantially from the standard impulse voltage waveshape used to test electric equipment insulation against lightning surges (1.2 / 50 microseconds wave). It is well known that the voltage withstand capability of insulation depends not only on the amplitude but also on the voltage waveshape. Different models have been proposed for predicting the strength of insulation subjected to impulses of non-standard waveshapes. One of the most commonly used is the \"disruptive effect model\". There are, however, different methods of applying this model, that is, different ways of estimating the parameters needed for its application. This thesis aims at evaluating the dielectric behavior of medium voltage insulators subjected to impulses of non-standard waveshapes, as well as at evaluating the main methods for predicting their dielectric strength against such impulses. For the analysis, tests were performed on a pin type porcelain insulator with rated voltage of 15 kV, using, besides the standard lightning impulse voltage waveshape, other s waveshapes selected based on the characteristics of measured and calculated lightning overvoltages. Modifications made to the circuit of a conventional impulse voltage generator allowed to obtain voltage waveshapes very similar to those of lightning-induced voltages measured in experiments conducted both in lines of natural size and in reduced model. The test results relative to the critical lightning impulse flashover voltage (U50) and the volt-time characteristics obtained for the positive and negative polarities of each waveshape are presented and discussed. The evaluation of the methods of determining the parameters of the disruptive effect model was based on comparisons between the volt-time curves obtained from the laboratory tests and those predicted by each method, for each of the selected voltage waveshapes.

As linhas de distribuição de energia estão freqüentemente expostas a sobretensões causadas por descargas atmosféricas diretas e indiretas. As formas de onda dessas sobretensões têm uma faixa de variação muito ampla e podem diferir bastante do impulso atmosférico normalizado utilizado em ensaios para verificação da adequação dos projetos das isolações dos equipamentos frente a sobretensões atmosféricas (1,2 / 50 microssegundos). É fato conhecido que a suportabilidade das isolações depende não só da amplitude como da forma de onda das solicitações. Diferentes modelos têm sido propostos para se estimar o desempenho das isolações frente a impulsos não normalizados, sendo o modelo do efeito disruptivo (disruptive effect model) um dos mais utilizados. Existem, contudo, diferentes métodos de aplicação desse modelo, ou seja, diferentes formas de se estimar os parâmetros necessários para a sua aplicação. Este trabalho visa avaliar o comportamento dielétrico de isoladores de média tensão e analisar os principais métodos para estimativa da suportabilidade desses equipamentos frente a sobretensões atmosféricas com formas de onda diferentes da normalizada. Para essa avaliação foram realizados ensaios em um isolador tipo pino, de porcelana, com tensão nominal de 15 kV, nos quais foram utilizadas, além do impulso atmosférico normalizado, outras ondas selecionadas com base em resultados de medição e de cálculo. Modificações realizadas no circuito de um gerador de impulsos de alta tensão convencional permitiram a geração de tensões com formas de onda bastante semelhantes às de sobretensões induzidas por descargas atmosféricas tanto em linhas de tamanho natural como em experimentos realizados com modelo reduzido. São apresentados e discutidos os resultados dos ensaios de tensão disruptiva de impulso atmosférico a 50 % e as curvas tensão-tempo (U x t) obtidas para cada impulso, considerando ambas as polaridades. A avaliação dos métodos de aplicação do modelo do efeito disruptivo foi realizada com base em comparações entre as curvas tensão-tempo obtidas nos ensaios e as curvas previstas por cada modelo, para cada uma das ondas selecionadas. / Overhead distribution lines are often exposed to lightning overvoltages, whose waveshapes vary widely and can differ substantially from the standard impulse voltage waveshape used to test electric equipment insulation against lightning surges (1.2 / 50 microseconds wave). It is well known that the voltage withstand capability of insulation depends not only on the amplitude but also on the voltage waveshape. Different models have been proposed for predicting the strength of insulation subjected to impulses of non-standard waveshapes. One of the most commonly used is the \"disruptive effect model\". There are, however, different methods of applying this model, that is, different ways of estimating the parameters needed for its application. This thesis aims at evaluating the dielectric behavior of medium voltage insulators subjected to impulses of non-standard waveshapes, as well as at evaluating the main methods for predicting their dielectric strength against such impulses. For the analysis, tests were performed on a pin type porcelain insulator with rated voltage of 15 kV, using, besides the standard lightning impulse voltage waveshape, other s waveshapes selected based on the characteristics of measured and calculated lightning overvoltages. Modifications made to the circuit of a conventional impulse voltage generator allowed to obtain voltage waveshapes very similar to those of lightning-induced voltages measured in experiments conducted both in lines of natural size and in reduced model. The test results relative to the critical lightning impulse flashover voltage (U50) and the volt-time characteristics obtained for the positive and negative polarities of each waveshape are presented and discussed. The evaluation of the methods of determining the parameters of the disruptive effect model was based on comparisons between the volt-time curves obtained from the laboratory tests and those predicted by each method, for each of the selected voltage waveshapes.