I.R. Jandrell

Influence of supply voltage frequency and magnitude on PD pulse parameters

A study on the influence of supply voltage magnitude and frequency on partial discharge (PD) pulse shapes is presented in this paper. Ultrawide band (UWB) time resolved PD pulse measurements were carried out on artificial PD defects using test voltage frequency range of 10-400 Hz and voltage range of 2-11 kV. The manner in which the PD pulse shape responded to changes in the test voltage characteristics depended on the defect type. The observations can be interpreted using the generally agreed theory of PD mechanisms. The knowledge generated in this work is valuable in the interpretation and comparison of PD measurements made at different voltages and frequencies. It also contributes to development of PD defect classification techniques based on the correlation between test voltage frequency and time-resolved PD.

Does a Sixth Mechanism Exist to Explain Lightning Injuries?: Investigating a Possible New Injury Mechanism to Determine the Cause of Injuries Related to Close Lightning Flashes

AbstractFive mechanisms have been described in the literature regarding lightning injury mechanisms. A sixth mechanism is proposed in this article, namely, lightning barotrauma. A simple laboratory experiment was conducted using ordnance gelatin for ballistic studies. Lightning was simulated in a high-voltage laboratory using an 8/20-microsecond current impulse generator and discharged through ballistic gel. Temporary and permanent cavity formations were confirmed. The cavities formed were directly proportional to the currents used. Findings suggest that a sixth mechanism of lightning injury, namely, barotrauma, should be considered.

Lightning medicine in South Africa

South Africa has a rich history of lightning research; however, research on the clinical and pathological effects and features of lightning-related injury (keraunomedicine or lightning medicine) remains neglected locally. By providing an overview of keraunomedicine and focussing on South African perspectives, we hope to raise awareness and propose that a concerted and co-ordinated attempt be made to report and collate data regarding lightning strike victims in South Africa.

Strategies for understanding lightning myths and beliefs

In South Africa, lightning kills people every year. People who work outdoors are particularly vulnerable to lightning strikes. Strategies need to be developed to reduce the number of people killed or injured by lightning. Many people, however, have firm views and beliefs about lightning and any strategy to improve their safety with respect to lightning, will have to take cognisance of these beliefs. This paper looks at the strategies that engineers can follow to familiarise themselves with the lightning beliefs in rural areas in Southern Africa.

Probabilistic interpretation of LDN confidence ellipses with reference to forensic applications

Data from lightning detection networks is often used for forensic purposes: to validate insurance claims or even to determine the cause of death. Stroke location and current estimates are subject to measurement error, and the dilution of precision is reported in terms of a median confidence ellipse and χ2 distribution. A method is presented to derive the probability density function from the reported statistics, and hence calculate cumulative probability densities. Two hypothetical cases are presented, with real lightning detection network data, to illustrate the obstacles constraining direct forensic application of the data.

Partial discharge spectral response to variations in the supply voltage frequency

Partial discharge (PD) spectral response to variations in the supply voltage frequency was experimentally investigated through laboratory-based tests. The PD spectral content of each defect type responded uniquely to variations in the sinusoidal supply voltage frequency in the range 20 to 400 Hz. The findings are interpreted using the theory of space charge dynamics in PD mechanisms. Prospective diagnostic applications of the findings include PD recognition using supply voltage frequency sweeps. Knowledge on supply voltage frequency dependency of partial discharges also helps in comparing PD diagnostic test results obtained at different test voltage frequencies.

A simplified model of the lightning performance of a driven rod earth electrode in multi-layer soil that includes the effect of soil ionisation

It is proposed that a single apparent resistivity value calculated from the steady state resistance equation and the measured steady state resistance can be used as a simplification for lightning current transient performance modelling of a driven rod earth electrode in multi-layer soil. The proposal is verified against results obtained using transient analysis of an equivalent circuit that includes the effect of soil ionisation and full-scale experimental results of current impulse tests on a single vertical earth rod in three-layer soil

Lightning myths in southern Africa

AbstractLightning kills many people in Africa every year. There is consensus in the literature that something should be done to raise awareness about lightning safety in southern Africa. This paper is the result of a study to find common myths, beliefs and misconceptions about lightning in southern Africa to determine whether they have any impact on lightning safety. It presents the most common beliefs, assesses whether they increase people’s risk and concludes with recommendations on which myths should be included in lightning safety material.

Leveraging a mobile culture for lightning awareness: The African context

Mobile telephones have transformed and revolutionised Africa in a way that is radically different to the impact that they have had in the developed world. Not only have mobile phones changed Africa, but Africans have appropriated the technology by finding innovative ways of using it, with a large focus on low-cost usage and texting. This emergence of a pervasive mobile phone and texting culture in Africa might provide an opportunity to disseminate lightning awareness information and weather warnings in areas where it could reduce the number of annual lightning fatalities.

Lightning risk analysis: Case study of endandgered animals

In January 2012, two highly endangered Mountain Bongos were killed by lightning in the National Zoological Gardens of South Africa. These animals are on the critically endangered list and therefore as many risks should be mitigated where possible. Understanding and calculating the risk associated with lightning to animals within the enclosure is performed using IEC 62305-2 methods. In addition an alternate method is proposed looking at lightning current parameters and lightning ground flash data to determine a median lethal limit for a particular environment. From this a lethal area percentage for an outdoor environment can be determined. This is found to be approximately 75% for the enclosure. This would indicate that lightning protection measures should be put in place in order to prevent further losses as a result of lightning.