On the possible variation of the lightning striking distance as assumed in the IEC lightning protection standard as a function of structure height

The effect of structure height on the lightning striking distance is estimated using a lightning strike model that takes into account the effect of connecting leaders. According to the results, the lightning striking distance may differ significantly from the values assumed in the IEC standard for structure heights beyond 30m. However, for structure heights smaller than about 30m, the results show that the values assumed by IEC do not differ significantly from the predictions based on a lightning attachment model taking into account the effect of connecting leaders. However, since IEC assumes a smaller striking distance than the ones predicted by the adopted model one can conclude that the safety is not compromised in adhering to the IEC standard. Results obtained from the model are also compared with Collection Volume Method (CVM) and other commonly used lightning attachment models available in the literature. The results show that in the case of CVM the calculated attractive distances are much larger than the ones obtained using the physically based lightning attachment models. This indicates the possibility of compromising the lightning protection procedures when using CVM. (C) 2014 Elsevier B.V. All rights reserved.

A Physical Model for Inception and Propagation of Upward Lightning Leader from a 1200 kV AC Power Transmission Line

UHV power transmission lines have high probability of shielding failure due to their higher height, larger exposure area and high operating voltage. Lightning upward leader inception and propagation is an integral part of lightning shielding failure analysis and need to be studied in detail. In this paper a model for lightning attachment has been proposed based on the present knowledge of lightning physics. Leader inception is modeled based on the corona charge present near the conductor region and the propagation model is based on the correlation between the lightning induced voltage on the conductor and the drop along the upward leader channel. The inception model developed is compared with previous inception models and the results obtained using the present and previous models are comparable. Lightning striking distances (final jump) for various return stroke current were computed for different conductor heights. The computed striking distance values showed good correlation with the values calculated using the equation proposed by the IEEE working group for the applicable conductor heights of up to 8 m. The model is applied to a 1200 kV AC power transmission line and inception of the upward leader is analyzed for this configuration.

Analysis of lightning current characteristics to investigate lightning strike damages to energy pipeline

Australia is one of the most lightning prone area on earth. Lightning strikes have been identified as one of the most common cause of energy pipeline damage in Australia. Therefore, a suitable protection schemes and mitigation strategies against lighting strike damage is very important for Australian pipeline industry. There are a number of research on lighting protection of establishment such as, power systems, buildings, and telecommunications systems, however, very few publications could be found which discuss about protection of pipeline from lightning strike. Assessment of effects in buried pipeline, due to lighting strikes is important. Existing models do not account adequately the effect of the characteristics of soil breakdown channels intercepted by the buried object. This paper aims to investigate the characteristics of lightning current on metal object under the soil of strike point so that lighting attachment to energy pipeline could be understand and a protection technique could be developed. Along with lightning current characteristics, lightning attachment process, distribution method, soil resistivity, propagation of lightning current in soil with a buried pipeline, pipeline electrical properties and other related areas and technologies is explored. The study shows that though there are some research on characteristics of induced on simple buried structures like narrow telephone cable or residential gas pipe, but no substantial research have been done on large comparatively complex structures like buried energy pipelines. Also dynamic behavior of soil and the object to be protected not been considered in protections schemes and experiments.

Analysis of the lightning attractive radius of power transmission lines through the use of a physically-oriented model

Models of different degrees of complexity are found in the literature for the estimation of lightning striking distances and attractive radius of objects and structures. However, besides the oversimplifications of the physical nature of the lightning discharge on which most of them are based, till recently the tridimensional structure configuration could not be considered. This is an important limitation, as edges and other details of the object affect the electric field and, consequently, the upward leader initiation. Within this context, the Self-consistent leader initiation and propagation model (SLIM) proposed by Becerra and Cooray is state-of-the-art leader inception and propagation leader model based on the physics of leader discharges which enables the tridimensional geometry of the structure to be taken into account. In this paper, the model is used for estimating the striking distance and attractive radius of power transmission lines. The results are compared with those obtained from the electrogeometric and Eriksson's models. © 2003-2012 IEEE.

Processo de attachment, densidade de raios e a ocorrência de flashover em linhas de transmissão de eletricidade

Esta tese refere-se ao uso de modelos de attachment de lideres (Leader Progression Model – LPM) para estimativa da distancia de salto, que, junto com dados de densidade de raios como coletado pelo sistema de detecção de raios do SIPAM, são usados para estimar a taxa de flashover em linhas de transmissão de eletricidade na Amazônia. O modelo de progressão de líder desenvolvido nesta tese é denominado ModSalto, que, para estimar a distancia de salto: 1- integra a densidade linear de cargas elétricas devida ao líder, proporcional a prospectiva corrente de primeira descarga (1º stroke) Ip, para determinar o campo elétrico produzido pelo líder descendente na estrutura sob estudo (para-raios, arestas, condutores, etc.); 2 – integra a distribuição imagem do líder descendente, fazendo uso da característica de poder das pontas como fator de estimulo e intensificação do campo elétrico devido a streamers nas partes aguçadas das estruturas sob estudo, para temporizar o momento do processo de attachment. O gatilho para o líder descendente, por hipótese, se deve a ejeção aleatória de pacotes de cargas elétricas em domínios turbulentos no interior das nuvens que recebem energia por processos de cascata da turbulência geral, e o comportamento do líder descendente, deve obedecer à equação da força de Lorentz, no espaço de campos cruzados elétrico devido às nuvens a cima e o campo magnético da Terra, que obriga as cargas do líder a desenvolverem movimentos cicloidais que podem explicar a natureza tortuosa do trajeto do líder descendente. Com o objetivo de formalizar dados consistentes de densidade de raios é feita uma reanalise do conjunto de dados coletado pelo LLS SIPAM de outubro de 2006 a julho de 2008 na região amazônica, com cerca de 3 milhões de eventos, comparando-os com dados de torres instrumentadas para evidenciar-se sua qualidade e usabilidade. Dados de elevação de terreno do SRTM da NASA são usados para gerar formula do raio de atração (Ra) das estruturas passiveis de serem atingidas por raios e para gerar formulas de área de atração, usadas para quantificar o numero de raios que provavelmente atingirão determinada estrutura, baseado no valor de densidade de raios (raios/km2/ano) na área em estudo.

Green fireballs and ball lightning

This paper presents evidence of an apparent connection between ball lightning and a green fireball. On the evening of the 16th May 2006 at least three fireballs were seen by many people in the skies of Queensland, Australia. One of the fireballs was seen passing over the Great Divide about 120 km west of Brisbane, and soon after, a luminous green ball about 30 cm in diameter was seen rolling down the slope of the Great Divide. A detailed description given by a witness indicates that the phenomenon was probably a highly luminous form of ball lightning. An hypothesis presented in this paper is that the passage of the Queensland fireball meteor created an electrically conductive path between the ionosphere and ground, providing energy for the ball lightning phenomenon. A strong similarity is noted between the Queensland fireball and the Pasamonte fireball seen in New Mexico in 1933. Both meteors exhibit a twist in the tail that could be explained by hydrodynamic forces. The possibility that multiple sightings of fireballs across South East Queensland were produced owing to fragments from comet 73P Schwassmann-Wachmann 3 is discussed.

Alexithymia, craving and attachment in a heavy drinking population

Up to fifty per cent of individuals with Alcohol use disorders (AUD) also have alexithymia a personality construct hypothesized to be related to attachment difficulties. The relationship between alexithymia, craving, anxious attachment and alcohol-dependence severity was examined in 254 patients participating in a Cognitive-Behavioral Therapy (CBT) program for alcohol-dependence. Participants completed the Toronto Alexithymia Scale (TAS-20), the Obsessive Compulsive Drinking Scale (OCDS), the Revised Adult Attachment Anxiety Subscale (RAAS-Anxiety) and the Alcohol Use Disorder Identification Test (AUDIT). MANOVA indicated that individuals with alexithymia reported significantly higher levels of total OCDS, obsessive thoughts about alcohol, and compulsive drinking urges and behavior, compared to the non-alexithymic group. Regression analyses found that anxious attachment partially mediated the relationship between alexithymia and craving. Anxious attachment may be a potential treatment target to reduce alcohol consumption in those with alcohol-dependence and alexithymia. Research Highlights ► There were significant relationships of alexithymia, craving and anxious attachment. ► Alexithymic alcoholics reported higher levels of craving and alcoholism severity. ► Anxious attachment partially mediated the relationship of alexithymia and craving.

Attachment in relation to affect regulation and interpersonal functioning among substance use disorder inpatients

Attachment theory has been conceptualised as an affect regulation theory, proposing that attachment is associated with the expression and recognition of emotions as well as interpersonal functioning. Previous research has reported affect regulation difficulties in substance use disorders and addiction has been considered an attachment disorder. However, scarce empirical research exists on the relationship of attachment in relation to affect regulation and interpersonal functioning in those with substance use problems. Thus, the objective of the present study was to investigate potential associations between attachment, negative mood regulation (NMR) expectancies, fear of intimacy and self-differentiation in substance abusers. The revised adult attachment scale (RAAS), the NMR expectancies scale, the fear of intimacy scale and the differentiation of self inventory were administered to a sample of 100 substance use disorder inpatients. Attachment accounted for significant variance in NMR expectancies and was also a strong predictor of fear of intimacy. The predictive utility of attachment also extended to self-differentiation, suggesting that attachment was strongly related to overall self-differentiation score, Emotional reactivity, Emotional cut-off and I position. These findings support attachment theory suggesting that attachment is associated with and predicts affect regulation abilities and difficulties in interpersonal functioning in a sample of substance use disorder inpatients. The inclusion and assessment of attachment appears to be important in the development of treatment programmes for substance abusing individuals.

Being Grateful : Does it Bring Us Closer? Gratitude, Attachment and Intimacy in Romantic Relationships

To date, little is known about the function of gratitude in romantic relationships. Being grateful has been demonstrated to provide a number of positive benefits for individuals; however, few studies have explored how grateful experiences may be beneficial in enhancing romantic relationships. This study explored the extent to which adult attachment moderates the relationship between dispositional gratitude and the experience of intimacy within romantic relationships. A greater disposition toward gratitude was expected to result in more frequent experiences of gratitude. It was also anticipated that experiences of gratitude would be associated with feelings of closeness. Participants (n = 156) were required to be currently in a relationship of at least six months duration and completed a series of questionnaires assessing dispositional gratitude, attachment and emotional intimacy. Moderation analysis revealed that although a positive, weak correlation existed between dispositional gratitude and intimacy, attachment did not moderate this association. It was concluded that further investigation of the experience of gratitude is necessary to understand the function of gratitude in romantic relationships. Methods focusing on specific experiences of gratitude in romantic relationships, and the associated feelings of closeness experienced by each partner, may yield more conclusive findings and may provide support for therapeutic approaches focused on enhancing closeness between couples by increasing experiences of gratitude.

Being grateful : does it bring us closer? Gratitude, attachment and intimacy in romantic relationships

This study proposed that levels of dispositional gratitude influence experiences of intimacy within romantic relationships and that this influence is moderated by relationship attachment. Gratitude, in this study, was described as feelings of appreciation associated with the perception that one had been the focus of another’s intentionally beneficial actions. A greater disposition toward gratitude was expected to result in more frequent experiences of gratitude. It was also anticipated that experiences of gratitude would be associated with feelings of closeness toward the one responsible for the beneficial act. Participants (n=156) ranged in age from 18 – 70 and, although required to be currently in a relationship of at least six months’ duration, each was studied as an individual. Participants included both males and females, in same-sex or other-sex relationships, and completed a series of questionnaires assessing dispositional gratitude, attachment and emotional intimacy. Moderation analysis was conducted using hierarchical regression and revealed that although a positive, weak correlation exists between gratitude and intimacy, attachment did not moderate that association. However, the measures used did not elicit sufficiently divergent responses. Thus neither complete exploration of the proposed association between gratitude and intimacy, nor of the moderation of that association by attachment were possible. In conclusion, further investigation of experiences of gratitude, particularly in relation to enhancing feelings of closeness, is necessary to understand the function of gratitude in romantic relationships. Methods focusing on specific experiences of gratitude in romantic relationships and the associated feelings of closeness experienced by each partner may yield more conclusive findings. In addition, such findings may provide support for therapeutic approaches focused on enhancing closeness between couples by increasing experiences of gratitude.