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This article is concerned with the application of human statistical techniques to risk engineering in the electricity distribution system in Australia. It examines legal negligence in terms of the cause of action, care and duty, and economic criteria. A mathematical hazard model of risk analysis is presented.

Decision making in respect of hazard and safety analysis in the face of uncertain data in the management of widespread distribution systems is focused on. The narrow interpretation by Courts of the “foreseeable event” has become the benchmark of liability where power system failures have resulted in loss of life, injury or destruction of property; occurrences, the prediction of which relates more to the probability of extreme event combinations than to the assessment of availability by classically‐oriented reliability statistics. The work outlines a computer‐based inferential procedure which combines adverse weather to a probabilistic assessment of failure resulting from a combination of contributing events. The technique utilises Monte‐Carlo simulation in assigning the adverse weather to common mode data analysis in the derivation of failure state conditional probabilities. Limited sensitivity studies have been performed using Northern Rivers Electricity, emphasis being placed on evaluating preventative maintenance as a function of optimal time intervals, priorities and costs.

The purpose of this paper is to propose a fast, accurate and efficient algorithm for assessment of transient behavior of grounding grids buried in horizontal multilayered earth model considering soil ionization effect.

The purpose of this paper is to develop a numerical simulation method to calculate the lightning impulse response of the grounding grid buried in a horizontal multilayered earth model. The mathematical model about the hybrid method based on PI basic function belonging to time domain is proposed in the paper; the mode can precisely calculate the lightning current distribution and lightning impulse response to grounding grids buried in horizontal multilayered soil model considering soil ionization effect. To increase computing efficiency, quasi-static complex image method (QSCIM) and its time-domain Green’s function closed form are introduced in the model.

The hybrid model is rather stable, with the respect to the number of elements used and with excellent convergence rate. In addition, because this mathematical model belongs to the time domain algorithm, it is very powerful for the simulation of soil ionization caused by high amplitude lightning current.

To increase computing efficiency, QSCIM and its time domain Green's function closed form are introduced in the model.

The mathematical model about the hybrid method based on PI basic function can precisely calculate the lightning current distribution and lightning impulse response to grounding grids buried in horizontal multilayered soil model considering the soil ionization effect.

Considering the soil ionization effect, the simulation calculation of lightning impulse response of substation grounding grid buried in the actual horizontal multilayered earth can effectively support the scientific and efficient design of lightning protection performance of substation grounding grid.

The hybrid model in time domain is originally developed by the authors and used to precisely calculate the lightning current distribution and lightning impulse response to grounding grids buried in horizontal multilayered soil model considering soil ionization effect. It is simple and very efficient and can easily be extended to arbitrary grounding configurations.

Surge protective devices are used to limit the maximum voltage on protected circuits. In the last decade, metal oxide varistors (MOVs) have been the most used protective devices. Since many of the outages experienced on sensitive circuits are due to overvoltages originated by the effects of direct and nearby lightning flashes, it is important to evaluate the reliability of such protective devices under lightning stress. Actually, MOVs are affected by ageing, essentially due to the number and amplitude of stresses, and also other factors such as overheating, pollution and humidity. The aim of this paper is to present a method, based on probabilistic arguments, to evaluate the ageing process of MOVs. The expected life, so obtained, can be used to decide when the MOV must be changed before its failure occurs (reliability assessment), since the main standards do not give definitive indications about such features. The estimated expected life can be used in the design of logistic/maintenance procedures.