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In this contribution, the influence of free radical concentration on the electrostatic charging tendency (ECT) of aged mineral oils is reported. A free radical reagent, 2,2 diphenyl-1-picrylhydrazyl, is used to assess the relative concentration of free radicals. Prior to the ECT measurement, the oil samples were subjected to various stresses (corona discharges, multiple arcs or local overheating). Different ASTM standards were considered to assess the physicochemical properties before and after stress applications. It is found that free radicals affect the ECT. The theoretical premises that, free radicals may contribute to the ECT, are experimentally confirmed under laboratory conditions. The reason why this information is important is that ECT can significantly affect partial discharge inception in in-service transformers.

The work presented in this paper is related to the project GEMUDE (Genérateur Multifonction de Décharge Electrique) which aims to design a universal high-voltage generator for electrical discharge studies. To design this variable high voltage source that operates in the frequency range of 0 to 1 kHz, the assessment of transformer losses represents a crucial phase during the design process. These losses in the coils and iron core of the transformer are closely related to the frequency and nature of the materials used. This paper presents a comparative study of transformer losses using analytical methods and experimental calorimetry measurements. Steinmetz empirical formula is used to estimate magnetic core losses whereas coil losses are evaluated by solving Maxwell equations. The main goal is to control these losses to limit the internal temperature rise in the transformer through the implementation of an efficient cooling solution. The results obtained by the analytical method were satisfactory which confirm the feasibility of measuring the power absorbed by the various electrical discharge devices upstream of the high-voltage transformer. This is because it turns out that the power of the generator in charge is the total power of the electric discharge and the transformer losses. This method, termed Power Disparity Method (PDM). In this paper, it is an easy and reliable way as compared with high voltage measurement methods.

The present paper exposes a methodology for cost comparison of metallic and earth return paths for HVDC transmission systems. The authors suggest a method based on an algorithm that can be used for any case of study. Two conceptions are taken into account by the algorithm: a bipolar circuit operating as mono-polar for emergency conditions and a circuit operating as mono-polar for normal conditions. The present method uses the approach of Similarity for cost estimation and allows providing the best option for current return. Similarly, it allows giving the break-even distance to switch from metallic to earth return path. This depends on energy cost and the two return path options costs. In order to calculate the energy loss in the earth return; contribution of the linear resistance, at the inter-electrode part, on the total earth resistance has been evaluated in view of large distances in the transmission field. This evaluation was performed (based on electrode dimensions and resistivity values) using COMSOL Multiphysics software. As a case study, an HVDC link carrying 1GW of Photovoltaic Power from the Algerian Sahara to Europe has been proposed. The link is evaluated considering various HVDC circuit designs and operation modes; namely an overhead line for the terrestrial part from the south to north of Algeria and a submarine cable across the Mediterranean Sea.

The history of controlling destructive insects in the twentieth century makes it clear that the difficulties we encounter today in dealing with these types of insects come from our almost total reliance on one single controlling method, namely the use of chemical insecticides. These toxic and suspected carcinogenic products pose a serious threat to agriculture and the environment. However, the possibility of directing researchers in developing a new way considered as more efficient, more selective and less toxic has proved to be possible. The principle of this approach is based on an attractive effect and an electric effect. Nevertheless, the development of a bio and selective electrical system requires taking into account certain parameters involved in the attraction of insects and electrical discharge such as the electrical impedance. The results showed that the threshold at which the insect is disturbed depends on its conductivity.

The relationship between the water used for energy production, including both electricity and sources of fuel such as oil and natural gas, and the energy consumed to extract, purify, deliver, heat/cool, treat, and dispose of water (and wastewater) is sometimes referred to as energy intensity (EI). The relationship is not truly a closed loop as the water used for energy production need not be the same water that is processed using that energy, but all forms of energy production require some input of water making the relationship inextricable. Industry reforms, increasing demand, and more recently climate change are bringing into sharp focus the links between water and electricity in unprecedented ways. Models for climate change indicate that rainfall could decrease by more than 20% by 2050, which would result in even greater worsening water shortages in different basins of Algeria. The construction of 70 dams planned will provide only small additional volumes. The particular challenge for Algeria in the coming decades will be to adapt to a decrease in renewable water resources. The country will have to carefully manage these resources. Mobilization of non-conventional water resources (desalination and wastewater reuse) will be a strategic component of future water policy. The development of unconventional resources and the management of water demand will increase more the energy consumption of the water sector. This consumption would reach nearly 12% of the country’s consumption and must be integrated dice now in the country’s energy forecasts. More coordinated planning and action will consequently be required between the water and energy sectors if further aggravation of the water deficit is to be avoided. Moreover, the revolution in renewable energy (solar power) in terms of technological development and costs may help reduce the consumption of fossil fuels and ensure reserves for future generations by fostering decentralized renewable energy projects for the energy supply of pumping stations.

Most plasma reactors are designed for research purposes and they are less appropriate for industry. To facilitate the engineering of an industrial reactor, an effective approach based only on the calculated Paschen curve, the simulation of the electric field and the breakdown reduced field is proposed. The results show that the experimental Paschen curve is different from the theoretical one; consequently the recalculation of the electric parameters is discussed. The experimental voltage/Current characteristic is used to identify the abnormal glow discharge regime and also to correlate the visual aspect of the discharge with its regimes.

The aim of the present paper is to show the way of computing the Maxwell capacitance when applying a DC & AC voltage and comparing it with the analytic equation given in literature and show the advantages of this numerical method over analytical solution by changing the nature of the dielectric from air to PTFE. So, we will see the influence of the dielectric constant into calculating the capacitor and the impedance. In the case of applying an AC voltage, we vary the power supply frequency from 50 Hz to 1 kHz, 1 kHz - 1 MHz, 1 MHz - 5 MHz.

Water and electricity are fundamentally linked. At a basic level electricity generation requires water, and water treatment and transportation use electricity. Historically, there has been little reason to understand the nature of these links, due largely to the presumption that water was not a threat to energy security, nor electricity a threat to water security. This presumption is now being challenged. Industry reforms, increasing demand, and more recently climate change – are bringing into sharp focus the links between water and electricity in unprecedented ways. General awareness of the links between water and electricity is increasing daily, as the ramifications of the links are being felt the world over: Society's ability to deal with the challenges and uncertainties arising from the links between water and electricity is being hindered by limited understanding of the nature of the links, and seeming lack of policy tools to effectively analyze them. This paper reviews comprehensively the links between water and electricity. Presents a classification system for identifying links. Using the classification system, this study further discusses these links by drawing upon examples from literature and follows with a synopsis of the nature of these links. With this background, the paper reviews and compares water-energy studies in terms of scope, objectives, methodologies and key findings, discusses major limitations of these studies and identifies important areas that would benefit from more in-depth research. This research contends that this type of approach is unsuitable in the longer term, particularly when examining complex and multidimensional issues like the water-energy nexus. This work suggests that the nature of the nexus should and can be explored from a wider perspective, by developing a suitable integrated methodological framework to serve as a platform for such exploration. The purpose of this paper, therefore, is to outline the development of such a framework. Introduces Integral Theory and discusses how Integral Theory has shaped the development of the methodological framework employed in this research. Presents the framework and describes the suite of methods.

A new optimization method of the investment cost of a distribution grid supplied by photovoltaic (PV) sources. This method consists of determining the optimal grid cables cross sections and the optimal grid supply point (GSP) position, such that the sum of the joule losses and the cables investment costs are optimized. The determination of these parameters are performed by the programming of analytical equations using Matlab software, taking into account the influence of technical and economical requirements on the choice of the cables cross sections and the possibility of using several photovoltaic generators (PVG) with separated grids for spaced loads from a long distance, by optimizing the grouping loads combination. The obtained results show that: for a lowest global investment cost, the optimal GSP is referred to the minimum cost center (MCC), for the grid joule losses minimization, it can be in the minimum joule losses cost center (MJLCC); or in the center of the minimum investment cost of cables (CMICC) in the case of the cables investment cost minimization. The adoption of the optimal cross sections, the optimal PVGs (GSPs) number and their optimal positions achieve significant economic gains in terms of the investment cost.

In this paper, we present a contribution to the electrical modeling of positive dc point-to-plane corona discharges in dry air (20%O2 and 80%N2) at atmospheric pressure. The electrical equivalent circuit of the proposed model is regarded as a variable resistor in series with a variable capacitor. The evolutions of the electrical parameters are obtained using a mathematical method of identification based on the recursive least squares algorithm. For the same experimental conditions, the comparison between the measured discharge current and the calculated currents obtained using the identified electrical parameters of the proposed equivalent model shows good agreement, which validates the model as well as the method of identification. To validate this work, results and discussions are given in two different operating points.

The water sector in Algeria has to date paid scant attention to the issue of climate change and is often unaware of its impact on future water resources. Studies will be needed to assess the impact and cost of climate change and draw up adaptation solutions. Forecasts are not optimistic. Models for climate change indicate that rainfall could decrease by more than 20% by 2050, which would result in even greater worsening water shortages in different basins of Algeria. The construction of 70 dams planned will provide only small additional volumes. The particular challenge for Algeria in the coming decades will be to adapt to a decrease in renewable water resources. The country will have to carefully manage these resources. Mobilization of non-conventional water resources (desalination and wastewater reuse) will be a strategic component of future water policy. The development of unconventional resources and the management of water demand will increase more the energy consumption of the water sector. This consumption would reach nearly 12% of the country׳s consumption and must be integrated dice now in the country׳s energy forecasts. More coordinated planning and action will consequently be required between the water and energy sectors if further aggravation of the water deficit is to be avoided. Moreover, the revolution in renewable energy (wind and solar power) in terms of technological development and costs may help reduce the consumption of fossil fuels and ensure reserves for future generations by fostering decentralized renewable energy projects for alimentation of pumping stations. Algeria has thus set itself by 2030 a share of renewable energy in the national energy balance of between 30% and 40%. The share of renewable power by 2023 will represent about 17% of installed capacity (5539 MW) compared to 4.74% in 2011 (540 MW).

This paper shows a new method for optimization of the general investment cost in a distribution network supplied by solar photovoltaic (PV) source. This method consists of first, determining, the optimal cross sections for electrical cables used between solar generator and loads and second, find the optimal placement of loads distribution center such that the cost sum of installation and exploitation, of the investment, are considerably reduced to its optimal value. Particular method has been presented in previous study, where the optimization of the solar generator placement, is based on network having identical cables cross sections. However, our work was performed on the general case in view of the influence of technical and economical cable cross sections, operating hours or time periods of loads and the possibility to use more than one solar generator with several separated networks. The supply point that corresponds to the lowest general investment cost is referred as the Optimal Loads Distribution Centre “OLDC” which can also be referred to the Optimal Volume Center “OVC” if the exploitation details are not known. The OLDC method was applied on several examples, one of the most general and difficult case is presented in this article. The results of the analysis are found satisfactory since the adoption of the optimal number of loads distribution centers in their optimal places, taking into account the operating hours of loads with time periods, helped reducing drastically the general cost of the investment.

In this contribution the influence of various stresses and their combined impact on the electrostatic charging tendency of oil is studied. Various physicochemical properties were measured according to ASTM Standards to detect changes in oil quality. A free radical reagent, 2.2 diphenyl-1-picrylhydrazyl (DPPH), was added to oil before and after the application of stresses to determine free radical concentration. The results obtained show that the application of stresses contributes to an increase in the electrification current. These results also demonstrate that electrification current is affected by the quantity of the free radicals.

Currently, energy consumption in the planet is high, public awareness of energy consumption, environmental protection and steady progress in the deregulation of conventional energy, distributed generation systems (based on hydrogen) have attracted increased interest. Fuel cell (FC) base and high-temperature systems also have great potential in future single-source or multi-source (hybrid- HSE) applications due to their rapid technological development and numerous benefits such as well, as the appreciable efficiency, low emission (greenhouse gases) and flexible modular technology. Dynamic models for the main components of the system, namely the photovoltaic (PV) energy conversion system, fuel cells, electrolysers, electric power interconnection circuits, protective battery, storage tank of hydrogen, the gas compressors are developed. Two renewable energy modes, a photovoltaic field and a solid oxide fuel cell (SOFC) or Dynamics of proton exchange membrane fuel cells (PEMFC) with hydrogen storage system for generating part of system electrical energy is presented. Feasibility of using fuel cell (FC) for this system is evaluated by means of simulations. The electrical dynamic model, temperature change and dual layer capacity effect are considered in all simulations. Photovoltaic system (PV) output current is connected to the bus. Using a MPPT (maximum power point tracker) which is an electronic DC to DC converter that optimizes the match between the solar array and utility grid. The proposed system utilizes an electrolyser (EL) to generate hydrogen and a tank for storage. Therefore, there is no need for batteries. Moreover, the generated oxygen could be used in FC’s system and other applications. Moreover, such as the photovoltaic system, it is possible to connect fuel cell (FC) output voltage to DC bus alternatively. A controller model is presented to control flow of energy of system, hydrogen and oxygen to FC and improve transient and steady state responses of the output voltage to load disturbances. Simulations are carried out via MATLAB/SIMULINK and results show that the load tracking and output voltage are acceptable.

Desalination of seawater is needed in Algeria, as an option to secure the supply of drinking water to populations in coastal cities and meet the rapid increase of demand for water in agriculture and industry sectors. The biggest constraints of this system are its energy consumption and environmental impacts due to the discharges of brine in the natural environment. Today, more than 17,000 desalination plants worldwide produce about 72 million m3/d, while the global production capacity of drinking water is about 600 million m3/d. In Algeria, the production of desalination plants amounts to 2.3 million m3/d. Operating costs are mainly affected by the power stations, but the significant decreases in costs makes desalination increasingly competitive. Any approach aiming to generalize desalination should be viewed with caution. Indeed, the option of large-scale desalination results in the consumption of large amounts of electrical energy. Practically all the additional electricity produced in Algeria is currently thermal, the risk of a sharp increase in greenhouse gases emissions and discharges of untreated brine is great. However, options of low CO2 emissions are possible. The spinnerets of the most efficient desalination should be promoted: reverse osmosis with optimization, in combination with thermal power plants, energy recovery, and improvement of existing installations. Renewable energies (wind, solar photovoltaic, and concentrated solar power) applied to desalination are tracks for the future, even if their development is linked to issues of funding and competitiveness. Desalination is thus presented as an option for adaptation to climate change; the adoption should not intervene in substitution to other possibilities of “sustainability”, such as the rational use of water. It should moreover favor the production of drinking water for human consumption.

For a better understanding of the flashover criterion and discharge elongation mechanism, an experimental study was carried out in order to find flashover voltage and current according to the pollution amount. A simulation study was then carried out to assess the electric field distribution in the vicinity of the discharge that corresponds to the flashover experimental values. The obtained results show that the average value of the electrical field in the flashover gap discharge-electrolyte is high compared with the average value obtained in works devoted to the study of air breakdown in the vicinity of an electrical discharge. The average field value of these two systems is lower than the average field value in a metal pin–water system. This result confirms that the presence of an electric discharge weakened the dielectric rigidity of the air. The maximum values of the electrical field in the vicinity of the discharge are high compared with the value of the disruptive field of air at atmospheric pressure. Flashover is, therefore, possible if the electric field distribution along the leakage distance is sufficient for discharge elongation by a progressive breakdown of the air, by Streamer or Townsend mechanism, between the discharge and the electrolyte.

In this contribution a particular attention is being given to the strategic objective for the establishment of a North Africa (NA) countries cooperation on water and clean energy superhighway as the solution to regional energy challenges, water shortages, climate change and other environmental problems arising from the current fossil-fuel heavy global energy paradigm. Advanced and technical know-how and resources of Japan, through the Sahara Solar Breeder (SSB) project, can facilitate to achieve sustainable development in the region, cooperation to accelerate and expand its research activity with ambitious quantitative targets for solutions between the growing water crisis in NA and energy resources (fossil and renewables energies (RE)). With global energy demand set to rise significantly over the next 15 years, there will be a pressing need for fresh investment in new output capacity across the entire water/energy supply chain. It is still believed and emphasized that Photovoltaic (PV) will be a significant contributor within a portfolio of energy sources in the coming 10–20 years and that SSB is providing science and technology that are poised to play a transformative role in providing clean and sustainable water/energy for the whole world. Japan's energy/water innovative strategy for NA is encouraging since problems cannot be solved by one country alone hence local, regional and global cooperation is crucial.

Using an electrical approach in the field of agriculture can be considered as one of the solutions in order to control harmful flying insects. This technique is based on the use of a bio and selective electrical insecticide whose principle consists in attracting insects by the light then get them electrocuted by an electrical discharge. Moreover, There are several parameters that affect the selectivity of electrical insecticide such as: the light, the most efficient, the inter electrode distance, where the insect is exterminated, and the electric current that passes through the insect’s body. In this paper, a simulation study was carried out concerning the distribution of the electric field between two electrodes in presence of particle conductor while focusing on the different body sizes. On the other hand, an experimental study was conducted on live locusts to determine the effect of electrical current on insect’s body taking into account the voltage and frequency. Finally, the results are discussed and analyzed in this paper.

The quality of life and safeness of the present and future generations are strongly intertwined with the availability of energy sources and the sustainability of the energy infrastructure. Energy consumption in developed countries grows at a rate of approximately 1% per year, and that of developing countries, 5% per year (Muneer et al., 2005 [1] ). Present reserves of oil and natural gas can only cover consumption at this rate for the next 50 years in the case of oil, and for the next 70 years in the case of natural gas. Therefore, one of the fundamental priorities for a country such as Algeria is to use several renewable energies (RE) sources and environmentally friendly energy conversion technologies. Algeria is endowed with large reserves of energy sources, mainly hydrocarbons and a considerable potential for the utilisation of RE sources especially with respect to solar energy. Algeria has the potential to be one of the major contributors in solar energy and become a role model to other countries in the world. RE are now one of the major elements of Algeria's energy policy and in view of boosting the national effort in terms of RE beyond 2011, Algeria has developed a national programme for the period 2011–2030 to promote concrete actions in the fields of energy efficiency and RE in line with the approach adopted by the government on February 3, 2011. Besides, it confirms Algerian's ambition to become an international hub for industrial and energy production and exportation in the solar sector. With this in mind, along with the environmental responsibility issues, public awareness gradually increased over the last seven years and alternative energy resources have become a new area of interest. As a tangible target, the Ministry of Energy and Mines (MEM) strategic plan aims to reach a 40% share of RE (mainly solar) in electric energy production by 2030. The various future projects are all factors that will undoubtedly give Algeria an important role in the implementation of RE technology in North Africa, the capacity for providing sustainable supply of cost-effective electricity from RE sources for the needs of the population, and the possibility of even exporting 10,000 MW to neighbouring and European market. This paper provides a detailed analysis of the existing renewable energy sector and a forecast for demand growth, additional capacity, investment requirements and Algeria's ambitious objectives of use of RE and environment protection. The paper also discusses the current energy scenario and explores the alternative energy like solar and wind to ensure energy security supply, reliability, greater efficiency in energy conversion, transmission and utilisation. Particular attention is paid to Algeria's global and sustainable solutions of the environmental challenges and the problems of conservation of fossil energy resources under the clean development mechanism (CDM) structure. The report also provides a detailed analysis of the existing renewable energy sector and a forecast for demand growth, additional capacity, and investment requirements

Effect of the hydrogen radical on the reduction of a silicon tetrachloride (SiCl4) source was studied. The hydrogen radicals were generated using a tungsten (W) filament in a generation chamber, and were remotely supplied to another reaction chamber. The density of the hydrogen radical was estimated from the optical transmittance of 600-nm-wavelength light through phosphate glass doped with tungsten oxide (WO3). Lifetime of the hydrogen radical seemed sufficiently long, and its density as supplied to the reaction chamber was estimated to be on the order of 1012 cm−3. Signal intensity of the peak corresponding to SiCl4 (m/z = 170) detected by quadrupole-mass measurement was confirmed to decrease owing to the reaction with the remotely-supplied hydrogen radical. This indicates the possibility that chemically-stable SiCl4, as one of the by-products of the Siemens process, can be reduced to produce silicon.

A device for catching insects, using a high voltage electrical discharge, called KAHRATRAP, is designed and build up by the first author of this paper. The aim of this paper is to describe the electrical operation mode of this apparatus such as the high voltage supply and the electrical discharge which this supply produces for the elimination of insects. We determined in this paper the most optimal color of the lamps of the device which give the best results. Moreover, we analyze the influence of climatic parameters such as temperature and humidity on the efficiency of the process. This apparatus was used during 4 months in a vegetable field, operating during the night from 18h to 6h to capture harmful insects. The reading of insect numbers is done according to a procedure using a binocular magnifying glass, an entomologist tool and boxes for the collection of insects.

In order to find the electrical size which determined the critical condition of flashover, the authors have examined the propagation of the discharge on surface under DC voltage in a new laboratory model which has a continuous and radial current distribution. This model is a vat having a circular sector form of variable angles, radiuses and depths filled by an electrolyte. The obtained results on this model show that for a given resistivity of electrolyte: if the current distribution in the horizontal plane is uniform according to the sector angle, the applied critical voltage and the critical current per unit of angle (1deg) are constant for all sectors of various angles, if the current distribution in the vertical plane is uniform according to the depth, the critical flashover voltage and the critical current per unit of the electrolyte depth (1 mm) are constant for all the depths. These results lead to the critical conditions of flashover to be determined by the current per unit of angle and per unit of electrolyte depth (A/deg/mm)

Resume La separation electrostatique des metaux et des materiaux isolants contenus dans un melange granulaire est une technique de plus en plus utilisee dans l’industrie du recyclage des dechets. L’objectif de cet article est double: (1) presenter la procedure utilisee pour la mise au point de nouvelles applications, en utilisant une installation pilote-industriel concue et realisee par les auteurs; (2) montrer l’interet de la separation electrostatique comme complement des procemecaniques de recyclage des dechets industriels. L’etude a ete effectuee sur des echantillons mis a la disposition par une entreprise algerienne specialisee dans la redes dechets de câbles electriques. Des experiences preliminaires ont permis d’etablir les valeurs limites des deux variables de controle du processus: la vitesse de l’electrode cylindrique tournante et la haute tension d’alimentation. Les essais en regime de pilote-industriel ont confirme l’efficacite de la separation electrostatique pour deux melanges granulaires cuivre-plastique.

The growing demands for improved fire safety, source material sustainability, environment friendliness, and asset life extension have driven the research and development efforts on natural/synthetic esters, less-flammable fluids. High flash point (HFP) liquids also known as “less flammable” liquids (natural/synthetic ester and silicon fluids) were then introduced. The aim of this contribution is to report some investigations onto the Electrostatic Charging Tendency (ECT) of some commercially available ester fluids. Comparison is made with mineral oil, as this is a fluid we are familiar with. The investigations were performed using a spinning disk system designed in our laboratory, in which the disk is coated on both sides with different cellulose paper. Recall that this system was adopted by CIGRE for international comparative measurements of both insulating liquid and solid transformer materials. The obtained results indicate that the electrification current vary according to fluids motion. This variation is very important at higher speeds (above 600 rpm). In most tests carried out, esters seem to generate more charges than mineral oil.

In this paper we study the influence of salts mixture on DC flashover voltage discharge characteristics. We used NaCl as principal salt and we adjoin it different salts. Results shows that mixture of salts gives different flashover voltage and current then NaCl on both polarity. A dimensional analysis has made for determining the relation between quantity of salt and constant of discharge N and n. The results of calculation shows that N and n are function of quantity of chalk and volume of CaCO3.

A dynamic model for predicting dc flashover discharge current behavior of electrolyte and ice covered insulating surfaces is presented. The model takes into consideration insulating geometry, pre-contamination level, electrical field on the front of discharge and characteristics of pollution. Assuming discharge behavior as a time dependant resistance, it is possible to determine leakage currents characteristics and time of flashover using Hampton criteria for propagating of discharge and Rumeli criteria for estimating the displacement of the discharge assuming that the electrical breakdown stress on the front of discharge will be determined by the streamer criteria. The simulated results show that the model is in agreement with experimental results and is more appropriate for high resistance of pollution for electrolyte and ice layer.

Our work concerns the study of the influence of the no uniformity distribution pollution of insulators surface on flashover probability and probability of occurrence of an earth-fault in a high voltage line. Initially, we presented the method which makes it possible to calculate the contamination flashover probability and the earth-fault probability including the effect of the no uniformity of pollution distribution. The results of calculations show that flashover voltage and flashover probability of insulators with no-uniform pollution distribution is more critical than the case of uniform pollution. Also, the earth-fault probability is not influenced especially by no-uniformity of pollution.

In the existing literature dealing with flashover simulation or theoretical studies, the discharge is considered to have a tubular form of uniform diameter, and its evolution is simply its foot displacement at the surface of the pollution or of the ice, while it maintains its tubular form. After presentation of the equivalent electric circuit for flashover simulation, an experimental study is presented, the purpose of which is to determine the difference between the theoretical dynamic features of flashover, based on the tubular-formed discharge assumption, and the real dynamic features. The results clearly confirm the difference between the two groups of dynamic features and that the theoretical dynamic features are the sum of the static points.

In flashover-modelling literature, researchers only take into account, the resistance of the pollution on the insulator, assuming that the current takes part in its totality and that the geometrical shape of its lines in the pollution does not have an influence on the phenomenon. In the paper, and after presentation of the equivalent electric circuit of flashover used in the literature, an experimental study and physical analysis are presented concerning this assumption in two sets of laboratory models: multidirectional models and circular-sector models. The results obtained allow us to confirm first that the form of the pollution and the distribution of leakage current lines are indispensable to flashover modelling; and secondly that flashover criteria and critical conditions in the literature are unjustified.

This paper describes a theoretical and experimental study which have been carried out with simple laboratory models to investigate the effect of the existence of a slightly conductive film on insulating surfaces.

The form of the discharge during its evolution on the pollution is important for two essential reasons: firstly to better know the physical mechanism of the evolution of the discharge, and secondly to verify the validity of the mathematical equations used to interpret the phenomenon of flashover. in the existing literature, the discharge propagates in a tubular form, its circular foot displaces or slips on the pollution. The mathematical equations modeling the system have been based on this tubular aspect. To verify the validity of this form, we measured the current during the evolution of the discharge in two experimental models. From the graphical analysis of the measured current I(t), we deduced that the discharge doesn't evolve in a tubular form but takes the aspect of a foot that lies down. Then the theoretical dynamic features calculated using the tubular dynamic aspect is only the sum of static independent points distinctly different from the experimental characteristic.