University of Craiova FACULTY of ELECTRICAL ENGINEERING
University of Craiova FACULTY OF ELECTRICAL ENGINEERING
Eng. Dumitru BROSCĂREANU
SUMMARY OF THE THESIS
Scientific coordinator Prof. dr. PhD G.A. CIVIDJIAN
CRAIOVA _ 2011 _
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
Content
Foreword ...... 2 Content ...... 3 Specific terms and expressions used ...... 7 1. Introduction. The use and objectives of doctoral thesis ...... 9 2. The current stage of regulations and research methods and establishing fire causes of electrical nature ...... 13 2.1. General questions …………………………………………………………… 13 2.2. Classification of causes of fires …………………………………………...... 13 2.3. Requirements for research into the causes of fire …………………...... …... 14 2.4. Establishing probable causes by research on-site fire …...... …. 15 2. 4.1. Procedural aspects …………………………………………………... 15 2.4.2. Tactical rules ………………………………………………………….. 16 2.4.2.1 General tactical rules …………………………..…………………... 16 2.4.2.2. Reguli tactice specifice ……………………………………………. 16 2.4.3. Aspects to be determined by investigator …………..………………… 16 2.4.4. Activities conducted by investigator ………………………………….. 20 2.4.4.1. Documentation ………………………………………..………...... 20 2.4.4.2. Research on the ground ……………...……………………………. 21 2.4.4.2.1. Activities during the intervention …………...... ……….. 21 2.4.4.2.2. Settlement activities after fire ………...... …… 22 2.4.5. Establish the probable cause of fire and the outbreak ……………….... 23 2.5. Methods and procedures used in fire research …………...... …………... 24 2.5.1. General logical methods ………………………….………………...... 24 2.5.2. Methods, processes and specialized operational means ………………. 24 2.5.3. Scientific methods and specialized technical ...... 24 3. Fire Statistics with ignition sources such as electric ...... 26 3.1. Fire statistics by category ...... 26 3.1.1. Statistics fire with ignition sources such as electricity in Romania between 2000 - 2005 ……………...... 26 3.1.2. Comparative statistical analysis of fires in 2007 in Romania, Russia, USA and the United Kingdom ...... 28 3.1.2.1. Statistical analysis of fires in 2007 in Romania ...... 28 3.1.2.2. Statistical analysis of fires in 2007 in Russia ...... 32 3.1.2.3. Statistical analysis of fires in 2007 in the United States of America.. 36 3.1.2.3.1. Brief review of fires in 2007 ...... 36 3.1.2.3.2. Graphical and tabular brief fires in 2007 and compared to the period from 1998 to 2007 ...... 37 3.1.2.4. Statistical analysis of fires in 2007 the United Kingdom ...... 42 3.1.2.4.1. Brief review of fires in 2007 ...... 42 3.1.2.4.2. Graphical and tabular brief fires in 2007 and compared to the period from 1997 to 2007 …………...... 43 3.2. Conclusions drawn from statistical analysis ...... 46 3.2.1. Comparison of common indicators ...... 46 3.2.2. Conclusions drawn from the comparative analysis ...... 49 4. On the ampacity of insulated conductors in conduit ...... 51 4.1. Introduction ...... 51 4.2. Conductor temperature ...... 51 4.2.1. Evaluation of cooling surface ...... 51
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 4.3. Heat transfer coefficient ...... 52 4.4. Ampacity of conductor in conduit ...... 54 4.4.1. Errors ...... 56 4.5. Conclusions ...... 56 5. Thermal field diffusion in one, two and three-dimensional half space ...... 57 5.1. Introduction ...... 57 5.2. One dimensional case ...... 57 5.2.1. Characteristic length of thermal field diffusion …...... 60 5.2.2. Thermal flux density ……...... 61 5.3. Two dimensional axisymmetric case ...... 61 5.3.1. Thermal field localization in 2D case ………………...... 63 5.4. Three dimensional spherical case ...... 64 5.4.1. Thermal field localization …...... 65 5.4.2. Thermal flux density ...... 65 5.5. Numerical applications of mathematical models of thermal diffusion in space field to minimize risks of fires ...... 66 5.6. Conclusions ...... 67 6. Modern systems and facilities of detection and signaling .... 69 6.1. General considerations ...... 69 6.2. Installation of fires detection and signaling ...... 69 6.3. Fire detectors …………...... 70 6.4. The process of evolution of a fire and detection opportunity …...... 71 6.5. The fire detection system and extinguishing ………...... 72 6.6. Detection systems with smoke suction ...... 73 6.7. Advantages of smoke detection systems with suction ...... 76 7. Intelligent building management in terms of defense against fires ...... 78 7.1. General considerations ...... 78 7.2. Integration into a technical management ...... 80 7.3. Detection systems by using multi - sensor detectors …………...... 81 7.4. Detection algorithm based on fuzzy logic ...... 82 7.5. The detection algorithm expert …………...... 83 7.6. Conclusions ...... 85 8. Active Lightning Protection systems ...... 87 8.1. Lightning rod with striking device ……...... 87 8.2. Realization lightning protection installations (IPT) with the lightning striking device (PDA) ...... 88 8.3. Types of lightning striking device (PDA) ...... 89 8.4. Inefficiency of lightning with striking device ...... 94 8.4.1. Strimmer starting from the rod grounded, without descending leader …. 97 8.4.2. Strimmer starting from the rod grounded in the presence of downward leader ...... 97 8.4.3. Generation leader ...... 98 8.4.4. Lightning devices ESE - early strimmer emission ...... 98 8.4.5. Peak beam impact in the development of reverse strike ...... 99 8.4.6. Influence of corona discharge on an electrode charged in an electric field 99 8.5. Conclusions ...... 101 9. Lightning protection using laser spark ...... 102 9.1. Introduction ...... 102 9.2. Laboratory studies ...... 102
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 9.2.1. Experiment between metal electrodes ...... 102 9.2.2. Experiment between metallic electrode and charged artificial aerosol cloud ...... 104 9.2.3. Experiments between two metal electrodes ...... 105 9.2.4. Experiments in the Sea of Japan ...... 105 9.3. Active lightning protection with lightning energy extraction device ...... 106 9.4. Conclusions ...... 109 10. Final conclusions and personal contributions. Future research directions …...... 110 ANNEX - Data transmission systems for fiber optic ...... 113 1. Nature of light ...... 113 2. The refractive index ...... 114 3. Geometrical optic and the fundamental laws of the geometrical optic ...... 114 3.1. Law rectilinear propagation of light ...... 115 3.2. Independent rays propagation law ……...... 115 3.3. Optical path reciprocity law ………...... 115 3.4. Snell-Descartes laws ...... 116 4. Wave optics and wave optics laws …………...... 116 4.1. Wave optics ……...... 116 4.2. Wave optics laws ………...... 117 4.2.1. Interference of light ...... 117 4.2.2. Diffraction of light ...... 117 4.2.3. Polarization of light ...... 117 4.3. Photonics optical ...... 118 5. Consequences of the laws of optics ...... 118 6. History fiber ……...... 119 7. General parameters of optical fiber ...... 120 7.1. What is fiber? ……...... 120 7.2. Advantages of fiber optics over conventional technologies …...... 120 7.3. Fiber components …………...... 121 7.4. Optical fiber typical dimensions...... 122 7.5. Variation ways of refractive index ………...... 122 7.6. Critical angle …...... 122 7.7. Acceptance angle ……...... 123 7.8. Numerical aperture ...... 123 7.9. Acceptance cone …...... 123 7.10. Ways of propagation ...... 123 8. Optical fiber types ...... 124 8.1. The number of modes in a multimode optical fiber ...... 124 8.2. Single-mode optical fiber ...... 124 8.3. Indoor optical fiber …...... 125 8.4. Outdoor optical fiber …...... 126 9. Phenomena in optical fiber ...... 126 9.1. Signal attenuation in optical fiber …...... 126 9.2. Attenuation in the material ...... 126 9.3. Dispersion ...... 126 9.4. Rayleigh dispersion...... 127 9.5. Modal dispersion...... 128 9.6. Chromatic dispersion...... 129 10. Optical fiber alignment problems ……...... 129 10.1. Losses caused by different numerical aperture ...... 129 10.2. Losses caused by different diameters of the optical core ...... 129 ABSTRACT - 4 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 10.3. Losses caused by lateral movement of the fibers ...... 130 10.4. Losses caused by longitudinal movement of the fibers...... 130 10.5. Losses caused by the angular displacement ...... 131 11. Measurements of optical fiber …...... 131 11.1. The decibel ...... 131 11.2. Insertion attenuation measurement ...... 132 11.3. Power budget …...... 132 11.4. The periodicity of the measurements ...... 133 11.5. Thresholds validation measurements ...... 134 11.6. The aging of optical fiber and passive elements …………...... 134 Bibliography ...... 135
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 1. The use and objectives of doctoral thesis
Recently, the energy consumption in general and the electricity in particular took a great extent, because of the wide range of home electrical consumers which appeared on the market and their extensively use in almost every home. With the advent of these very diverse consumers, leading consequently to an increase in electricity consumption, taking into account that to achieve the complexity of the schemes significantly increased, the risk of fires due to electrical causes has grown. This is based on the fact that with the increasing number and the complexity of consumers and electrical power consumption, no action was taken to adapt their facilities to supply electricity, referring to the fact that they remained largely undersized. Consequently, due to overloading existing circuits, also increases significantly the risk of fires that are based on electrical causes. This follows from the statistical analysis of fire from the four evaluated states and compared common indicators presented in Chapter 3, entitled "The fire statistics with electrical nature ignition sources". The results obtained in research work and establish the causes of fire are largely based on deepening phenomena from the theoretical point of view and then the implementation of physical models in traces research (fingerprints) of fire. During the research of the fire’s causes which I participated and those specific continuing education as during individual training, I have noticed, making certain statistics of fire by various criteria that, the problem of establishing the electrical nature fire’s causes is treated somewhat superficially. In most cases of fire’s causes research, after following the set out steps by the methods of research and after removal of fire’s causes, duly technically justified, which could not "be find" in those situations, if it remaind for thorough research the electrical nature fire’s causes, establish very easy as probable fire’s cause "electrical short circuits" that does not correspond to reality in quite many cases. This can be proved in more detailed research of electrical installations and equipment involved, taking into account the specific characteristics of this "phenomenon" - electric short circuit. The category of electrical nature fire’s causes, can be classified as follows: - The deterioration of electrical insulation; - The arcs; - The short circuit power; - The electric spark; - The thermal effects of electric current; - Underdimmensionnement of the current paths; - The static electricity (static bodies); - The lightning. Taking into account the static electricity and lightning, whose manifestation does not imply a mandatory the existence of installation for electricity transportation or electricity consumers, on the other hand, those which involves such facilities, we have tried to analyze the electrical nature fire’s causes, which are closely related to each other by phenomena that occur and are also quite difficult to distinguish. The necessity of this work comes from determining precisely electrical nature fire’s causes, each leading to different measures to be taken for removeing the possibil production of these causes in future. For example, establishing the electrical spark as probable cause of fire, does not automatically lead to researching the electrical protective equipment for their eventual replacement, because the heat from it is extremely small, almost negligible, this need the presence of an explosive atmosphere around a device which produced it, which need a very small amount of energy to ignite. Not the same can be said for an electrical short circuit, which is totally different form phenomena that accompany it point of view. In this case the heat transfer produced by Joule effect, has a very important role, taking into account the
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE intencity of short-circuit electric currents. In establishing such a fire’s cause, is necessarily checked the circuit protection equipment. Therefore, we consider that, to establish correct and precise the electrical nature fire’s causes, will not lead on false tracks the inspection of prevention and it will lead to improving transportation systems and power supply and greater security for their work.. Taking into account all these arguments, in this paper, we presented in Chapter 2, entitled "Current stage regulations and how to research and establish the electrical nature fire’s causes" which are regulations in the field and the ways and specific methods for research of the fire’s causes in general, which are requirements for research into the fire’s causes, their procedural aspects, the specific tactical rules, what the investigator must follow, the field research method, the activities to be performed during fire extinguishing and after the fire liquidation and establishing the probable cause of fire. I realized then, in Chapter 3, entitled " Fires statistics with electrical ignition sources" a statistical comparative analysis of fire with ignition sources such as electricity in four different states, based on statistical analysis of the fires with electrical causes in Romania during 2000 - 2005, a brief analysis of fires in Romania, Russia, USA and the UK in 2007, creation of common indicators and comparing them, followed by some conclusions drawn from comparative statistical analysis, where resulted the emphasizing, the high percentage of the electrical nature fires and, in further research, we tried to find some ways to minimize the risk of electrical nature fire’s causes. In this sense, we performed research on determining the maximum allowable current in conductors insulated cables using an original formula based on analysis of data extracted from tables presented in the normative for design and execution of the electrical installations with voltages up to 1000 V a.c. and 1500 V c.c. - I7-2002, and interpolating these values, a subject treated in Chapter 4, entitled "On the ampacity of insulated conductors in conduit", chapter in which we presented the relative differences (errors) too, between current carrying values in the tables of normative data I7-2002 and those calculated with the formula suggested. 4. On the ampacity of insulated conductors in conduit 4.1. Introduction It is well known that the current-carrying capacities of conductors depends on the steady state maximum admissible temperature supported by the used insulating materials, on the external temperature, on cooling surface and on the equivalent coefficient of thermal transfer. The equivalent coefficient of thermal transfer α is in general difficult to evaluate, because it depends on the cooling surface shape, thermal conductivity of insulating materials, geometrical dimensions and set up. This is why we used the data given for various norms, well verified in long practice to evaluate the product of equivalent heat transfer coefficient and the equivalent cooling surface. 4.2. Conductor temperature 4.2.1. Evaluation of cooling surface We will consider the conductor cross-section not round but a square with the side a. In this case the cross-section area of a package of n conductors with s cross section area, (n - perfect square), will have the following total area and external perimeter: 2 == = 4, napansnS (4.1) So, extending this propriety to all the integers, the external cooling area per unit length of a group of n parallel s-cross-section conductors can be considered approximately equal to: ≅ 4 nsS (4.2) c Due to relatively small cross-section of conductors, in steady state, the temperature θm can be considered uniform distributed in conductor cross-sections and in all the conductors of the package. For the same current I in all the (identical) conductors, the difference between this temperature and the external temperature θ0 can be determines as follows: ABSTRACT - 7 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
ρ 2nI =θ−θ=θ ]K[ (4.3) 0m α Ss c Where ρ is the conductor material resistivity at temperature θm. Replacing Sc from (4.2) we obtain: ρ 2 nI =θ−θ=θ ]K[ 0m 5.1 (4.4) 4α s The heat transfer coefficient α has two components: convection heat transfer coefficient and radiation heat transfer coefficient, proportional with the 3-th power of the absolute temperature. In our case, at relatively low temperatures, dominant is the convection heat transfer coefficient. This coefficient decreases with the 1 to 0.25 power of characteristic length. For simplicity reason we will assume that it decreases with 0.5 power of the conductor thickness: α ⎡ W ⎤ =α 0 ⎢ ⎥ (4.5) 4 s 2 Km ⎣⎢ ⎦⎥ Replacing in (4.4) this coefficient the following expression is obtained for the temperature growth in current carrying conductors: ρ 2 nI =θ ]K[ 25.1 (4.6) 4α0 s It results for the maximum admissible current: θ s 25.1 I 2 α= 0 [A] (4.7) ρ n
4.3. Heat transfer coefficient The heat transfer coefficient α0 will be determined to fit the maximum admissible currents given in I7 norm from 2002 [93]. In the new norm from 2009, the maximum admissible currents for conductors in conduit are not given and the use of given by conductor producer ratings is recommended. In fig. 4.1 the current-carrying capacities of PVC or rubber insulated conductors in conduit are given according to I7-2002 [93].
Fig. 4.1 Cu and Al ampacities for 60° C and 25° C ambient (I7-2002): 0 rows: conductor cross section [mm2]; 1-4 rows: current-carrying capacities in [A] for 2, 3, 4 and 5 or 6 conductors in conduit.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE For the evaluation of the equivalent heat transfer coefficient on the surface of the conductor, the values of admissible currents (fig. 4.1) was used to determine the quantity α0 with the equation: ρ 2 nI ⎡ W ⎤ 0 =α (4.8) 25.1 ⎢ 1.5 ⎥ 4 θ s ; ⎣ Km ⎦ The results are presented in fig. 4.2 and 4.3 and the mean values of α0 and their constant of variation for copper and aluminum are given in table 4.1. The electrical conductivity was considered as in table 4.1.
Table 4.1 Unit Cu Al σ = 1/ρ at 20°C MS/m 59.5 37.7 Mean α0 and its W variability ratio for n = 2 1.5 1.135 5.8 % 1.037 8.9 % Km Mean α0 and its W variability ratio for n = 3 1.5 1.049 9.5 % 0.989 8.6 % Km Mean α0 and its W variability ratio for n = 4 1.5 1.008 9.3 % 0.946 9.2 % Km Mean α0 and its W variability ratio for n = 6 1.5 0.952 10.1 % 0.884 9.3 % Km Overall mean α0 and its W variability ratio 1.5 1.036 10.8 % 0.964 10.7 % Km It can be seen in fig. 4.2 and 4.3, as well as in table 4.1, that despite the scatter of data, they are almost the same for all the cross section area. Also the average values are enough close to each other and for both materials the value of α0 can be considered equal to 1.
Fig. 4.2 Values of α0 determined from the ampacity of copper conductors for 2 up to 5 of them loaded versus wire cross section
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
Fig. 4.3 Values of α0 determined from the ampacity of Al conductors for 2 up to 5 of them loaded versus wire cross section The equivalent heat transfer coefficient α increases several times for small conductor cross-sections and is about 7% smaller for aluminum conductors (fig. 4.4). 4.4. Ampacity of conductor in conduit 1.5 Taking into account that we can consider α0 = 1 W/(m K), a general approximate formula can be proposed for the conductor current-carrying capacity evaluation, issuing from (4.7): θ s 25.1 I = 2 [A] ; s [m2], ρ [Ω m] (4.9) ρ n
It can be seen that in general, the ampacity is proportional to the square root of difference of temperatures of conductor and ambient and inversely proportional to the number of loaded conductors in the conduit at 0.25 of power. The ampacity of aluminum conductors is almost 80% from the copper conductors with the same cross-section and insulation.
Fig. 4.4. Heat transfer coefficient versus wire cross section
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE More practical, if the conductor cross section is taken in mm2 and the wire conductivity σ = 1/ρ in MS/m, the equation (4.9) becomes: s 25.1 I 356.0 θσ= [A] ; s 2 ],[mm σ [MS/m] (4.10) n
Fig. 4.5. Ampacities of copper insulating conductors in conduit, calculated with formula (solid line) and I7-2002[93] (points)
Fig. 4.6. Ampacities of aluminum insulating conductors in conduit, calculated with formula (solid line) and I7-2002 [93] (points) 4.5. Errors The relative differences between the values of admissible currents given in I7-2002 and calculated with formula (4.7) and α0 from table 1 are given in fig. 4.7. It can be seen that for 2 to 4 conductors in conduit almost all the errors are smaller than ~10%. Only for 5 or 6 loaded conductors the error are up to 16%.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 01 2 3 0 9.108 3.498 1.948 -2.003 1 2.83 -6.282 -6.487 -16.334 012 3 2 5.494 -2.71 -5.91 -11.566 0 3.044 1.366 2.117 -6.421 3 1.579 -5.716 -6.479 -13.474 1 -1.847 -5.545-8.651-14.142 4 1.729 -4.306 -6.243 -13.656 2 -0.634 -1.03 -1.528-12.538 5 1.646 0.218 -1.1 -9.369 3 -1.316 1.22 -5.543-12.23 ErCu = 6 0.572 -2.421 -4.975 -11.65 % 4 -1.315 -6.673-8.249-14.266 7 4.235 -3.101 -5.792 -12.184 ErAl= 5 0.457 -0.845-3.137-9.529 % 8 5.583 0.956 -1.561 -7.596 6 4.506 1.046 -0.576-10.088 9 1.382 0.978 -1.137 -7.363 7 3.869 0.338 -1.601-9.238 10 9.54 3.648 1.607 -5.649 8 10.5623.412 0.944 -6.719 11 9.061 9.177 6.555 -0.989 9 10.2118.272 5.832 -1.435 12 6.367 8.194 6.031 -3.621 10 10.5187.654 5.385 -2.017 13 5.447 5.403 3.15 -4.192 11 5.434 4.916 2.73 -4.746 Fig. 4.7. Differences between the given in I7 [93] ampacities and calculated with (4.7), reported to the calculated ones. First column – 2 conductors, second – 3, third – 4, last column 5 or 6 conductors.
4.6. Conclusions 1. The performed analysis shows that the given in [93] ampacities (fig. 4.1) are not so exact, because the curves related to the heat transfer coefficient, resulting from them, are not monotone (fig 4.2 and 4.3) and the obtained values has up to 10% variability. 2. The similar analysis, made for the new edition of the norm I7 (2009) and IEC standard [40] for cables, shows a monotone curves of the parameter α0 and much smaller variability of the values. 3. The equations (4.7) and (4.9), obtained from average values of heat transfer parameters, with some simplified assumptions can be used for a rough evaluation of current-carrying capacity of a large range of conductors or cables from various materials. 4. Such evaluations can be useful in emergency conditions, in particular for quick identification of electrical causes of fires or explosions in buildings or factories realized on the basis of old materials and norms, like analyzed norm [93]. 5. For 5 and 6 loaded conductors in the conduit the errors given by proposed formulas are larger and the given in [93] ampacities are smaller with up to 10% than calculated with formula (4.7).
Also, compared, we researched the thermal field propagation in one, two, three- dimensional half space too, analyzing how thermal field propagation in homogeneous space, presenting some numerical applications of mathematical models of thermal field diffusion in space to minimize risks of fire and how to solve inverse problems in the next Chapter 5.
5. Thermal field diffusion in one, two and three-dimensional half space
5.1. Introduction Systematical, unitary analysis and graphical presentation of thermal field propagation in homogeneous media can facilitate some inverse problems solving, as fire localization, its causes identification and various homogeneous elements refractoriness. For instance, when the electrical short-circuit occurs the contact is rapidly melting around the arc foot and a half spherical or cylindrical isothermal surface of radius r0 with constant temperature θ* (equal to metal melting point e.g.) can be considered (the hot layer).
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE We will consider a half infinite homogenous space with 1, 2 and 3 dimensions and c, γ, λ, specific heat, density, thermal conductivity and zero temperature, subjected to a step of temperature θ*⋅1(t) at radius r0 and zero temperature at infinity. For given time t after the temperature step is applied, we will define a temperature penetration depth as λ t = ; atax = (5.1) c γ
Using the defined penetration depth, in the paper is analyzed how close to the simplest one dimensional case are the two other cases when r0 increases.
5.2. One dimensional case A thin half infinite homogenous rod (wire) with A cross-section and c, γ, λ, ρ, specific heat, density, thermal conductivity and electrical resistivity, carrying a constant direct current I, is considered (Fig. 5.1a).
Fig. 5.1: Samples of one and three-dimensional thermal field: contact heating by electric arc The heat transfer equation, which results from energy conservation, considering the Fourier and Newton laws, can be written as follows for a volume V with the mass m, cooling surface S and heat transfer coefficient α [20]: ∫∫∫ γ dvc θ∂ θ p V cm 2 a −θΔ= + ; =τ = ; ρ= jp (5.2) ∂t τ c γ ∫∫αdS α S S In our case, the current density j is constant along the wire and, using the index 0 for the quantities at ambient temperature and considering the temperature coefficient of resistivity αR, this equation becomes [24]:
θ∂ θ p0 λ cm 2 a −θΔ= + ; a = I =τ ; = 00 IRP (5.3) ∂t τI c γ c γ α−α PS 0R where m and R0 are the wire mass and resistance per unit length at ambient temperature and τI the equivalent local time constant, taking into account the wire material resistivity dependence on temperature αR , for constant current.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
Fig. 5.2: Errors of eq. (5.11) versus eq. (5.9) Fig. 5.3: Temperature versus time for several distances, calculated with (5.9) – solid line and (5.11) - dot [24] We will consider isothermal all the rod cross-sections and the temperature of the rod depending only on x and t. For the Laplace transform T(x, s) of the temperature the following equation results from (5.3):
d2T ⎛ 1 ⎞ T p ⎜s +− ⎟ + 0 = 0 2 ⎜ ⎟ (5.4) dx ⎝ τI ⎠ a s λ The boundary conditions for this problem are the following:
θ* sT = sT ),(;),0( ∞<∞ (5.5) s The solution of this ordinary equation with constant coefficients is the sum of general solution of homogenous equation and the particular solution Tm of no homogenous eq:
⎛ θ* ⎞ ⎛ 11 ⎞ p 1 ),( TsxT += ⎜ − ⎟ eT β− x; ⎜ s +=β ⎟; T = 0 m ⎜ m ⎟ ⎜ ⎟ m ⎝ s ⎠ a ⎝ τI ⎠ c γ ⎛ 1 ⎞ (5.6) ⎜ ss + ⎟ ⎝ τI ⎠ To find the original of this expression we will apply the translation theorem of Laplace transform [7] (5.5) to the following Laplce images, which can be found in [7] at (5.3) and (5.10), in terms of error and complementary error functions (Erf and Erfc) [24]:
′ e− α s ⎛ 1 α′ ⎞ ⇔ Erfc⎜ ⎟ ′ ≥α 0)Re(; ⎜ ⎟ s ⎝ 2 t ⎠ (5.7) − α′ s 2e ⎡ −i α′β′ ⎛ 1 α′ ⎞ i α′β′ ⎛ 1 α′ ⎞⎤ ⇔ −β′t ⎢ee Erfc⎜ − β′ ⎟ + eti Erfc⎜ + β′ti ⎟⎥ ′ ⎜ ⎟ ⎜ ⎟ s + β ⎣⎢ ⎝ 2 t ⎠ ⎝ 2 t ⎠⎦⎥ The temperature of the uniformly cooled wire, carrying a constant current I, will be:
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
⎡ −x x ⎤ * ⎛ ⎞ ⎛ ⎞ t / τ− I θ−θ m ⎢ xτ t xτ t ⎥ m []1),( −θ=θ zetx )(Erf + ⋅ Erfc⎜ ze − ⎟ + Erfc⎜ ze + ⎟ 2 ⎢ ⎜ τ ⎟ ⎜ τ ⎟⎥ ⎢ ⎝ I ⎠ ⎝ I ⎠⎥ ⎣ ⎦ (5.8) p τI0 x / xx τ m =θ ; z == ; τ ax τ= I c γ 2 ta t /2 τI
5.2.1. Characteristic length of thermal field propagation
The quantity t = tax was called the temperature penetration depth in t seconds. It depends only on the (homogeneous) material and the considered time t. For time equal to the local thermal time constant it can be called characteristic length of thermal field propagation and depends on dimensions, cooling conditions and material characteristics or on temperature diffusion coefficient a and local thermal time constant τI. * For θm<< θ (for example without current θm = 0) and the above equation becomes [24]: ⎡ −x x ⎤ θ* ⎛ t ⎞ ⎛ t ⎞ tx ),( =θ ⋅ ⎢ xτ Erfc⎜ ze − ⎟ + xτ Erfc⎜ ze + ⎟⎥ I =0 ⎢ ⎜ ⎟ ⎜ ⎟⎥ (5.9) 2 ⎝ τI ⎠ ⎝ τI ⎠ ⎣⎢ ⎦⎥ The square bracket from (5.8) or (5.9) can be approximated as follows:
⎡ TX −z 2 ⎤ 2T −z 2 T −z 2 ⎢Erfc()z + ⎥ Xe )ch( − ≈ XzXe )ch()Erfc()sh( − Xe )sh( ⎣ π ⎦ π π (5.10) x t X ;1 T =<= < 1 xτ τI For poor cooling conditions (α ≈ 0) the time constant and the characteristic length tend to infinity and for small times the terms t/τI and x/xτ in (5.7) tend to zero. For heat transfer coefficient α tending to zero the equation (5.8) becomes [24]: x x tx ),( θ≈θ *Erfc z z == =α 0 ( ); (5.11) 2 ta 2 xt The last equation gives up to 1% larger values of the temperature than (5.9), while x < xτ and t < 0.01 τI. The errors for several values of t/τI are given in fig. 5.2. In fig. 5.3 and 5.4 can be seen that the two formulas (5.11) and (5.9) agree enough well up to relatively small times (t/ τI < 0.1).
Fig. 5.4: Temperature versus distance, calculated for several times with (5.9) – solid line and (5.11) - dot [24]
ABSTRACT - 15 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 5.2.2. Thermal flux density The thermal flux density across the wire results from the derivative of (5.8) with respect to x: (5.12) .
2 ⎧θ e +− Tz )( + ⎫ λ− ⎪ m ⎪ q = ⎨ * ⎬ π ta θ−θ m ⎡ − X ⎛ −− )( 2 ⎞ XTz ⎛ +− Tz )( 2 ⎞⎤ ⎪ ⎢ ⎜ )(Erfc +−π× eTzte ⎟ ⎜ )(Erfc ++π− eTzte ⎟⎥⎪ ⎩⎪ 2 ⎣ ⎝ ⎠ ⎝ ⎠⎦⎭⎪
When τI tends to infinity X and T approach zero and the thermal flux density becomes: * θλ −z 2 q = e (5.13) I ∞→τ π ta
In particular, for x = 0 we have: * θλ * c γλ q x=0 = θ= ; [W/m2] (5.14) I ∞→τ π ta πt
The thermal energy absorbed by the rod is
2 * 2 * = =γθ λγθ tcAtaAcQ ; [J] (5.15) π π
5.3. Two dimensional axisymmetric case In this case, at constant current, the current density decreases inversely proportional to the radius r. Hence the conductor losses density drops off inversely proportional to r2 and can be neglected. The cooling surface is very small and the time constant can be considered infinite. Due to the symmetry, the temperature will be considered as function only of radius and time and the equation (5.2) becomes [24]: θ∂ a ∂ ⎛ θ∂ ⎞ θ = ⎜r ⎟ + (5.16) ∂t ∂rr ⎝ ∂r ⎠ τ For the Laplace transform of the temperature with respect to the time T(r, s) it results the following modified Bessel equation [17]: 2 d T d1 T 2 ⎛ 11 ⎞ T =ν−+ ;0 rx ; ⎜ s +=νν= ⎟ (5.17) d x2 x d x a ⎝ τ ⎠
We will consider the temperature of r0 radius cylindrical surface at t = 0 instantly rising from 0 to θ* and constant after that. As in previous case, at r infinite the temperature must rest finite one. * * θ sTttr =⇒⋅θ=θ sTt ),(),(;),0()(1),( ∞<∞⇒∞<∞θ (5.18) 0 s The solution of this problem is expressed by modified Bessel functions of zero order:
ABSTRACT - 16 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
* θ 0 ν r)(K srT ),( = (5.19) s Κ ν r00 )( Unfortunately there is not closed form of the original of this expression, but, using the best located nodes [43], it can be enough exact calculated, using the equation: ⎛ ⎞ ⎜ r ⎟ K0 pi 10 ⎜ ta ⎟ ),( θ≈θ * Atr ⎝ ⎠ ∑ i i=1 ⎛ r ⎞ K ⎜ 0 p ⎟ 0 ⎜ i ⎟ ⎝ ta ⎠
0 0 0 0 0 0 1 5.225+15.73i 1 -10.349+4.111i (5.20) 2 5.225-15.73i 2 -10.349-4.111i 3 8.776+11.922i 3 186.327-253.322i p = 4 8.776-11.922i A = 4 186.327+253.322i 5 10.934+8.41i 5 -858.652+2.322i·103 6 10.934-8.41i 6 -858.652-2.322i·103 7 12.226+5.013i 7 1.552·1033 -8.44i·10 8 12.226-5.013i 8 1.552·1033 +8.44i·10 9 12.838+1.666i 9 -868.461+1.546i·104 10 12.838-1.666i 10 -868.461-1.546i·104
The coefficients Ai and the nodes pi are calculated in [43] with 20 significant digits and approximately given in the next table.
Fig. 5.5 Temperature versus the distance from hot Fig. 5.6: Fraction of temperature at several xt from surface for cylindrical isotherms the hot layer versus its radius r0/xt for cylindrical (solid) and spherical (dashed) case
ABSTRACT - 17 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 5.3.1. Thermal field localization in 2D case In assumed conditions the temperature θ* will spread to all the half space at infinity time. At given time t the hot region (with temperature larger than θ) can be determined from fig. 5.5, where θ/θ* is given as function of distance from constant temperature hot surface with radius of this surface as parameter. When r0 increases the thermal field approaches the field in one-dimensional case. In
Fig. 5.5 can be seen that for 0 > 10 tar the one-dimensional case can be considered. At smaller r0 the temperature decreases more with distance. For all r0 the temperature falls to * * less than θ ·Erfc(1) = 0.157·θ at distance larger than 2 xt and than 0.0047 θ* at distance larger than 4 xt [24]: ⎧ * ⎪ 156.0 0 >−θ 2 tarr tr ),( <θ (5.21) ⎨ * ⎩⎪ 00468.0 0 >−θ 4 tarr In fig. 5.6, the fraction of temperature θ* at distance from hot layer of several times the penetration depth is given as function of hot layer radius over the penetration depth (2 z0). The dashed lines are the same for three-dimensional case. The FEM analysis of complex configurations can be limited at the domain where the temperature is higher than environmental. In function of the hot layer relative radius
= 00 / tarx and the selected level of precision, the necessary distance from the hot layer can be determined in this figure. For example, if 1% of maximum temperature can be considered 0 and x0 = 0.2, the considered for FEM domain must have the external border at least at 3 xt from the hot layer.
5.4. Three dimensional spherical case In this case the conductor losses density drops off with 1/r4 and the cooling surface is also very small. The time constant for a homogeneous sphere with isotherm surface and r radius is [24]: γ rc =τ (5.22) s 3α As in previous case we will neglect the heating effect of the current and the cooling. With these assumptions the equation (5.2) for central symmetry can be written as follows:
θ∂ a ∂ ⎛ 2 θ∂ ⎞ λ a =θΔ= ⎜r ⎟; a = (5.23) ∂t r2 ∂r ⎝ ∂r ⎠ c γ
Changing the function θ = θ1/r this equation and its Laplace transform will be: 2 2 θ∂ 1 θ∂ 1 d T1 s = a ; = T1 (5.24) ∂t ∂r 2 d r2 a The initial conditions of the problem being:
* r0 srT ),( θ= (5.25) 01 s the solution for the image will be
ABSTRACT - 18 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
s −− rr )( * r0 0 a (5.26) srT ),( θ= e 1 s Using the equations (5.6) the closed form for original function can be obtained and the thermal field will be given by the equation:
* r0 − rr 0 tr ),( θ=θ ;)(Erfc zz = (5.27) r 2 ta
Fig. 5.7: Temperature versus the distance from hot Fig. 5.8: Differences between the relative temperatures surface for spherical isotherms [24] in 1D and 2D (solid) or 3D (dashed) versus the relative distance between layers, for two values of relative hot layer radius z0
5.4.1. Thermal field localization Comparing the fig. 5.5 and 5.7 can be observed that the three-dimensional thermal field is more localized than the cylindrical one. In both cases, at given instant, the temperature distribution with radial distance from the hot surface is under the curve of one- dimensional case, approaching it when the radius r0 of hot surface increases. The difference between the temperature in one-dimensional case θ1 and θ3 for three- dimensional case is given by the equation resulting from (5.11) and (5.27):
θ−θ 31 zz 0− = − zz 0)Erfc( (5.28) θ* z
In fig. 5.8 the differences between the temperature in one-dimensional case θ1 and θ2 for two-dimensional case, respectively θ3 for three-dimensional case are given (in relative units) as functions of the radial distance, for two values of z0. It can be observed that the errors in 2D case are two times smaller than in 3D case.
ABSTRACT - 19 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 5.4.2. Thermal flux density In 3D case the thermal flux density results from (5.27):
r ⎡ −zr 2 )exp( ⎤ q *λθ=θ∇λ−= 0 z)Erfc( + 2 ⎢ ⎥ (5.29) r ⎣⎢ π ta ⎦⎥ The total thermal flux entering in the half space will be, considering the hot layer 2 area A = 2 π r0 ⎡ ⎤ 2 dθ * r0 1 2 πλ−= rq 0 r0 ⎢12 +θλπ= ⎥ (5.30) dr π ta r0 ⎣⎢ ⎦⎥ And the energy ⎡ ⎤ * 2r0 2 0 ⎢trQ +θλπ= t ⎥ (5.31) ⎣⎢ πa ⎦⎥
5.5. Examples Example 1
The short –circuit in copper conductor can last up to 10 seconds. Which minimal distance from the hot layer must be adopted for FEM analysis domain to obtain a detailed solution of thermal field with 0.1% of θ* precision? The less concentrated thermal field is the one-dimensional. The thermal penetration dept for t = 10 s in copper (a = 118 mm2/s) is
xt =⋅= 3.3410118 mm (E1)
From fig. 5.6 it results that the minimal distance from hot layer must be at least 3.5 xt =120 mm. For r0 < 0.2⋅xt = 6.9 mm in two-dimensional case and for r0 < xt = 34 mm in three- dimensional case the distance can be reduced to 3⋅xt = 100 mm. In three-dimensional case for r0 < 0.02⋅ xt = 0.7 mm the distance can be taken equal to the penetration depth, i.e. 35 mm.
Example 2
The distance between the contact and the copper conductor insulation is L = 150 mm. How much time will pass after contact melting up to the moment when the temperature near insulation will reach 10% of θ* ? From eq. (5.11) or in fig. 5.5 it can be seen that, in one-dimensional case and without cooling effect, z-z0 must be 1.164. It results: L2 1502 t = = = s2.35 2 2 (E2) − zza 0)(4 ⋅⋅ 164.11184
Example 3
ABSTRACT - 20 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
An electric arc made a r0 = 9 mm radius circular hole in a large homogeneous steel sheet with temperature diffusion coefficient a = 20 mm2/s and melting temperature θ* = 1500°C. Which temperature will be after 90 s at 100 mm from the hole center?
In fig, 5.5 or using eq. (5.20) it can be seen that in two-dimensional case, neglecting the cooling effect we will have respectively: r − 9100 θ tax == mm42 z 0 1.0 zz =−== = ≈ 05.007.1 t 0 0 * (E3) 2 xt ⋅ 422 θ Up to 90 s the temperature will not exceed 1500·0,05 =75 °C.
Example 4 The hot surface with r0=5 cm has a constant temperature θ*. After 1 hour the temperature at d=20 cm is 0.3 θ*. What is the temperature propagation coefficient a ?
Fig 5.9. Temperature versus fraction of d and r0
d ⎫ = 4 ⎪ r0 ⎪ ⎬ z0 =⇒ 1.0 θ = 3.0 ⎪ (E4) θ * ⎭⎪
2 2 r0 5 xt 25 2 t = 3600 s xt == = 25 cm a === 174.0 s/cm 2 z0 ⋅ 1.02 t 3600
5.6. Conclusions 1. Neglecting the internal losses and surface cooling, the temperature localization and spread profile in one, two and three dimensional homogeneous space is similar if the relative distance z-z0 from the hot layer is taken as variable and the hot layer relative radius z0 as parameter.
ABSTRACT - 21 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 2. In one-dimensional case the thermal field propagation is given by equation (5.8) for the rod with current and equation (5.9) for the rod without current. 3. For negligible cooling effect (α ≈ 0) the eq. (5.11) can be used. It gives up to 1% larger than exact values of the temperature, while x < xτ and t < 0.01 τI. The corresponding errors are given in fig. 5.2 – 5.4. 4. For the 2D case (without current) a new approximate formula (20) is proposed (5.20). 5. For 3D case without current the exact formula (27) can be used (5.27). 6. In fig. 5.5 and 5.7 can be seen that in the 2D case the temperature decreases faster with the distance than in the one-dimensional case and in 3D case it decreases faster than in the 2D case. 7. The 3D thermal field is the most localized. In both cases 2D and 3D the temperature profile at given time approaches the profile of one-dimensional case when the radius of constant temperature hot radius increases. The larger is z0, the closer is the thermal field to the one-dimensional case. For z0 > 10 (or r0 > 20 xt), the one-dimensional case can be considered with an error smaller than 2.3% for 2D case and two times smaller error for 3D case. For z0 > 1 the errors are respectively 16.6 % and 8.3 % (fig. 5.8).
In Chapter 6, entitled "Modern signaling and detecting systems and installation" we tried to introduce some novelties in the field, making some remarks about the modern signaling and detecting systems and installation, we presented an analysis of fire detectors, the development of a fire and detection opportunity. Here we presented in detail the operation of smoke exhaust detection systems and benefits of these systems. Also, to minimize risks of electrical nature fire’s causes, we performed several studies on the management of intelligent buildings form point of view of defense against fire, which we have systematized in Chapter 7, entitled "Management of intelligent buildings from point of view of defense against fire", where we presented the integration in a technical management system and a detection system using multi-sensor detectors, followed by a concrete example of an expert system running on a detection algorithm, based on fuzzy logic.
8. Active Lightning Protection systems
In the same context, also to minimize risks of electrical nature fire’s causes, in Chapter 8, entitled "Protection systems (lightning) active" is presented the operation mode of active lightning with starting device (PDA), the realizations mode of lightning protection installations (IPT) with active lightning with starting device, several types of active lightning with starting device and also presents a critical analysis of the active lightning with starting device inefficiency, where we presented which are the minimum conditions to be fulfilled for the occurrence of back stroke leader. 8.4. Inefficiency (lightning) active - with lightning striking device. After the above mentioned in this Chapter, it should be noted that some experts have pointed to the inefficiency in the operation of these systems of protection (lightning) active - with lightning striking device, which does not show an increase of protection from lightning rod simple. Their arguments are presented and analyzed below. Lightning typical parameters:
ABSTRACT - 22 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE • H ≈ D ≈ 3 km • Rc ≈ 0.5 km, Qc ≈ 10 C • 90% of lightning are negative • U(H) ≈ -290 MV • U(H-Rc) ≈ -180 MV
Fig 8.7. Dipole model of cloud [10]
Lightning = limit case of long spark. Several decades ago the main danger was considered the high temperature channel, provoking fires and explosions. Nowadays Lightning Electro Magnetic Pulse (LEMP):
LEMP – di/dt ~ 1011 A/s
Electromotive voltage induced in a loop with an area of 1m2 at a distance of 10m from the current path through which current flows is such:
di μ S di LU 0 ≈≈= 2 kV t 2d π r dt
r should be increased as much as possible !
Fig 8.8. Main danger of lightning
Increased distance is expensive: r is related to h.
P < 0.005 h < 150 m P < 0.05 (A. Akopian)
0 = 85.0 hh 0 = 92.0 hh
⎛ hx ⎞ ⎛ hx ⎞ rx −= )002.01.1( ⎜hh − ⎟ x 5.1 ⎜hr −= ⎟ ⎝ 85.0 ⎠ ⎝ 92.0 ⎠
Fig 8.9. Radius protection lightning rod's height.
ABSTRACT - 23 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE Protection zone of two vertical rods can be determined using the following formulas: P < 0.005 h < 150 m P < 0.05
⎧ , < hlh ⎪ 0 ⎧ 0 < 5,1, hlh hmin = ⎨ ⎛ 3h ⎞ h 17,0 +− , >− hlhl hmin = ⎨ ⎪ 0 ⎜ ⎟() >−− 5,1,5,114,0 hlhlh ⎩ ⎝ 10000 ⎠ ⎩ 0 () ⎧ < 5,1, hlr ⎧ x , < hlr ⎪ x ⎪ d = − hh d = − hh x ⎨r min x > 5,1, hl x ⎨r min x , > hl ⎪ 0 h ⎪ 0 ⎩ min ⎩ hmin
Fig 8.10. Protection zone for two vertical lightning
Horizontal wire protection zone can be determined using the following formulas:
P < 0.005 h < 150 m P < 0.05
0 = 85.0 hh 0 = 95.0 hh (8.3) ⎛ hx ⎞ ⎛ hx ⎞ rx −= )0025.035,1( ⎜hh − ⎟ x 7,1 ⎜hr −= ⎟ ⎝ 85.0 ⎠ ⎝ 92.0 ⎠
For two wires placed at a distance l from one another have the following formula:
⎧ , < hlh ⎪ 0 hmin = ⎨ ⎛ 5h ⎞ (8.4) h0 ⎜ 14,0 +− ⎟(), >− hlhl ⎩⎪ ⎝ 10000 ⎠
The height of the starting orientation is more related to lightning strike generating inverse (upward leader) than the electric field irregularities, as can be seen in Fig 8.11.
ABSTRACT - 24 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
Leader trajectory can be arbitrary :
back stroke
Fig 8.11. Lightning orientation height
It’s useful to: • Early generate the back stroke • Increase its rate of growth
8.4.1. Streamer initiation from grounded rod, without leader
Necessary condition: • corona current > 10 mA [1]; • Average rate of electric field below charged cloud: dE ⎡ kV ⎤ = 2t ⎢ ⎥ dt ⎣m⋅s⎦ • Even at 100 m height the corona current is 50 times smaller than critical value for streamer flash: Streamer occurrence impossible!
Fig 8.12. Necessary condition
8.4.2. Streamer flash from grounded rod, with descending leader
In this case things change radically, because over the cloud field overlaps the field produced by head downward leader that is growing rapidly (down to the ground is made in 15 to 20 ms).
ABSTRACT - 25 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE • Leader starts at h = 3 km, radial displacement 0.3 km, with v = 200 km/s, charge density 0.5 mC/m, 15 ms. • Streamer flash can occur after 12 ms from descending leader start. • Electric field at ground level increases only 1.5 times ΔE0≈10 kV/m, • ΔU0= ΔE0 t ≈1000 kV
dE • Main contribution is of: 0 dt Corona current at the end of the same rods as shown in Fig 8.12. the downward leader descent Fig 8.13. Streamer appearance in the presence of downward leader
Decreasing the control voltage • The descending leader increased the corona current to critical value;
dE0 • The corona current is: cor ≈ ECi 0 dt
• This is tempting: the same current and streamer flash can be obtained with 20 kV and 0.1μs front. • Streamer initiation conditions:
dE h·ΔE [kV] Δt [μs] 0 0 E0 dt 1000 12000 28·104 20 0.1 28·104
It is tempting to get a significant decrease in control voltage (20 kV instead of 1000), capable of providing leader, increasing the slope (reduction of the time of the front of 2500 times). Such a device can be easily achieved and therefore poses no problems generating a streamer. But not every leader can generate streamer!
8.4.3. Leader generation
• For leader generation an ~1 m streamer is necessary or ~ ΔU0 = 400 – 500 kV • In case of 20 kV the voltage on streamer ΔU0 is only 220 kV - not enough for leader generation. • Hundreds kV pulse is necessary!
ABSTRACT - 26 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
Voltage distribution on the top of 100 m rod at streamer occurrence due to descending leader (up) and high slope 20 kV pulse (down)
Fig. 8.14. Leader generation by descending leader and high slope 20 kV pulse
8.4.4. ESE (early streamer emission) lightning devices
They have the following characteristics: • Pointed conic peak, on which a pulse voltage is applied from included, firm “known how”, source. • The storage capacitor is charged by corona current, occurring in thunder cloud electric field. • The several mm insulation cannot support more than 20-30 kV, so backstroke leader cannot be stimulated. • It rests the pointed peak radius.
8.4.5. Impact of peak radius on backstroke development
• The start of streamer flash is strongly influenced by the peak radius. • Unfortunately for r < 1 cm, the influence of peak radius on occurring of viable ascending leader is negligible. • In conclusion we can say that: The use of early streamer emission devices cannot enlarge the lightning protection zone; • Similar results were obtained in [47], [55].
Fig. 8.15. Impact of peak radius on backstroke development [2]
ABSTRACT - 27 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE 8.4.6. Influence of corona on charged electrode electric field
• Generarea de lideri gemeni
ΔU ⎛ l ⎞ ⎜ ⎟ m EE 0 +≈ E0 ⎜1+≈ ⎟ r ⎝ 2r ⎠ Fig. 8.16. Conductor in an electric field [10]
Corona onset el current corona ion mobility field electrode radius kV cm2 Ec 30. i400.μA r0 3. cm b1.5. cm Vs.
∂ρ r r ρ rr ==+ ;;0)div( ρ r = jvEbvv ∂t r ρ ∂ρ E = 0;div ⇒= ε 0 ∂t
1 3 − rri 3 )( rE )( = 4 Er 2 + 0 r 2 0 c 6 bεπ 0 i ρ r)( = 3 − rri 3 4 2 ()0 4π 0 Erb c + 6πε0 b
Fig. 8.17. Influence of corona discharge
ABSTRACT - 28 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
• In conclusion, Corona bar the leader initiation and accelerate the leader propagation.
Corona development
• For r0 << r < Rf
i 1 3iε tU )( rE )( ≈ ρ r)(; ≈ 0 )(; REtU ≈= 6πε rb r 8π rb f ff 3 0 tU )( )( ttUb ≈= bEbv = tRtvR )(;; = ff ff f 3Rf 3
Fig. 8.18. Corona development
• Example:
bA U ;)( τ vttAt ==⇒<= const. 2 f cm 3 A =1 MV/s, h =100 m, b =1.5 tU )( ⋅sV = tEtvttR )(;~)( = f f f f t 1 s ⇓= f tR )( U =1 MV, i = 390 μA, v = 7.1 m/s, b f 2 2/3 i = 6 επ ERb f0 = 2 επ 0 U = επ f0 ~2 ttAv R = 1.7 m, E = 47.0 kV/cm 3t f f
Avoiding corona adverse effect: • Corona impediment of ascending leader initiation can be avoided if a electrically connected part of HV electrode is shooting through the corona at 2 m up, with a velocity of 20 m/s. • Similar effect could be obtained with a continuous laser spark.
In Chapter 9, entitled " lightning Protection using laser spark" we illustrated a few laboratory studies on some experiments (between two metal electrodes, between a metal electrode and an artificial cloud aerosol charged) and devices in terms of lightning protection using laser induced spark, we analyzed a patent on the active lightning energy extraction device and have revealed using laser spark to direct lightning strike to the exit elements in order to increase the degree of protected objects assurance.
9. Lightning protection using laser spark
9.1. Introduction One of recent advanced developments in active lightning protection is the use of optical breakdown of air by laser radiation for favorable safety orientation of lightning stroke. In the paper a patented proposal is analyzed in the light of some results of recently performed experimental studies.
ABSTRACT - 29 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE The laser spark can be visually observed if a ruby or neodymium laser gigantic pulse beam with around 1 J energy and half amplitude duration of 30 ns is concentrated in a spot with radius of about 0.1 mm. This means a peak power of P = 33 MW. The efficient value of electric field in light wave results from Poynting vector to be more than 6 MV/cm: 2 E μ0 HES ; z0 ==×= 0 c Ωπ≈μ= ][120 z0 ε0 (9.1) 120P P 0 SzE =≈= ≈ ]MV/cm[3.641.19 r πr2
This is approximately than 200 times more than the breakdown electric field in the case of DC electric field, which is about 30 kV/cm, the same as in the case of high and ultrahigh frequency fields. Various laser types used for spark generation AND their radiation wavelength are listed in the following table. Table 9.1 Laser type KrF CO Nd Ti-Sapphire Rb 2 excimer Plasma discrete discrete cont discrete cont structure λ [µm] 10.6 1.06 0.8 0.694 0.248
9.2. Laboratory studies 9.2.1. Experiment between metallic electrodes
In the years 1972-1976 on the external test stand of St. Petersburg Polytechnic University [72], using an optical quantum generator GOS-1001 laser and large focus distance optical system, a long high ionized channel was obtained with 2 GW laser beam (50 ns, 100 J). With optical amplifier, having a multiplication coefficient 1.5 – 2, the maximal energy in the pulse was 160 J and the mean power 5 GW, with beam divergence less than 1΄. With this installation a horizontal laser spark of 60 m length was obtained, composed from many brightly lit regions with the length of several cm. To direct vertically this laser spark two total internal reflection prisms was used. Because of beam energy absorption in the prisms only 1 m length vertical optical spark could be obtained, in which the high ionized plasma rest during about 25 µs. In case of a good synchronization of laser with the source of high voltage pulse generator, this time is enough for the accumulation in the spark channel of a spatial charge of opposite to the voltage pulse sign, as it happens in the case of classical metallic rod with the same dimensions. If the corona inception electric field at laser light frequency is about Ei = 6 MV/cm, the largest radius of concentrated 5 GW laser beam should be less than: 120 P r ≈= 1 [mm] (9.2) m E i The positive high voltage pulse of 2.7 MV and the front time 3.5 ms was applied to the 2 m diameter lattice sphere, disposed at 10 m above the ground. The tests were mate in two steps. First the setup and the dimensions of the models of protected objects was selected for which the increasing of protective rod height with 1 m (largest length of vertical laser spark) is more efficient (largest difference between the probabilities of stroke to the protected object). In the second step, the 3.8 m height of the lightning protection rod was increased by 1 m laser spark. The laser was activated when the leader induced charge on the protected object reached a known critical value. First time the test were made without laser spark, afterward with laser spark and finally with a 4.8 m metallic rod. The tests showed that the presence of ABSTRACT - 30 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE the 1 m length laser spark decreases the probability of the stroke to protected object from 0.26 to 0.08, i. e. three times. Similar result (p = 0.12) was obtained with the 4.8 m metallic rod. Table 9.2 Number of discharges Number of To Probability of Rod height, m To object To earth tests rod object damage 3.8 307 79 102 126 0.26 4.8 125 15 57 53 0.12 3.8+spark 50 4 21 25 0.08 The tests confirm the possibility to (partially) replace the lightning protection rod with a laser spark and use it for lightning stroke orientation.
9.2.2. Experiment between metallic electrode and charged artificial aerosol cloud
Fig. 9.1: Experience setup [67] 1. Aqueous negative charged aerosol generator, exit nozzle 6 mm diameter 2. Grounded metallic plane 3. Cloud of charged aerosol 4. 100-580 mm rod with spherical or conic top 5. Low inductivity shunt 4 or 10 Ω 6. Spherical mirror 7. Digital camera 8. Video camera 9. Tektronix TDS 220 oscilloscope 10. Channel discharge 11. String sensor for electric field 12. Dynamic antenna for cloud charge monitoring wit S8-17 storage oscilloscope The interaction between laser spark and the lightening discharge is analyzed in [67]. The experimental investigation demonstrated that an extended (0.3 – 0.5 m) laser- induced spark, having a discrete structure, initiated in the vicinity of a grounded rod may intercept the channel of a leader discharge, arising from the grounded electrode toward an artificially highly charged aerosol cloud. The interception occurs when the electric field intensity near the electrode is close to the value required for the emergence of an upward positive leader. When the laser-induced spark was developed in position A, no correlation was observed between the spark and the emergence or development of an upward discharge from the grounded electrode (for electric field intensity from 16 to 20 kV/cm). When the spark was developed in the vicinity of grounded electrode top (position B), a correlation was revealed between the emergence of the spark and the development of the main discharge between the
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE cloud and the rod (from electric fields ranging from 12 to 16 kV/cm). Only bottom part of the leader discharge was intercepted by the laser spark, while the plasma formation closest to the cloud was not involved in this process. Several µs after optical breakdown, a flash of streamer corona was observed. In the following 2 – 4 µs this corona transforms in to leader which is followed by the 1 µs main discharge after 1 -3 µs. The experiences presented in [67] as the previous results cited there, demonstrate that the presence in the region of a laser induced spark in the charged cloud-grounded electrode gap causes an acceleration of the leader discharge propagation. The leader charge in the presence of a spark was several times lower than in its absence, probably because that the spark heats the air in front of the leader and accelerate the decay of negative ions.
9.3. Active lightning protection with lightning energy extraction device -Patent description- In fig. 9.4 the setup of the proposed device is shown and its function is illustrated in fig. 9.5, where transparent arrows show the signal orientation and the black ones the direction of the energy. As lightning diverter is used one vertical metallic cylinder (6) with a high permittivity dielectric thick glass (7) inside. The inside surface of dielectric glass is partially covered with earthed conducting layer 8 and the upper rest of the surface is ribbed to increase the flashover voltage. The cylindrical tube 6 is insulated from earth and connected to the upper end of the transformer T primary winding with earthed bottom end. The capacitance C between the cylindrical diverter 6 and the internal conducting coating 8 and the inductance of the transformer T primary winding form an LC oscillating tank. In the center of coated portion of the dielectric glass is a controlled moving diachronic mirror, whose normal to the reflecting surface forms a free varying sharp angle with the axis of the glass. In front of the mirror at least two lasers with coaxial beams are fixed: one for extended optical spark, preferable working in infrared range and the other one for atmosphere scanning, to detect critical charge density accumulation in clouds. The axis of the reflected beams must be able to describe a circular upturned cone with the tip in the center of the mirror and tangent to the upper margin of the metallic cylinder 6, when appropriate position of the mirror is assured.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
Fig. 9.4: Active lightning protection with lightning energy extraction device setup 1. System for static control of electric field intensity in air 2. Infrared pulse laser (Nd ~ 103 J e.g.) for long laser spark 3. CO2 laser for atmosphere backlight and scanning 4. Diachronic mirror 5. Optical receiver 6. Grounded through transformer (T) primary winding metallic cylinder – lightning divertor 7. High permittivity dielectric glass 8. Grounded metallic coating 9. Internal ribbing to avoid the surface discharge 10. Insulator 11. Mirror protection air jet makers 12. – 14 Rectifier, current converter (CC), battery PDU - Power and distribution unit, CS – control system The secondary winding of the transformer T is connected to the rectifier 12 charging the condenser 13, which charges the accumulator 14 through the converter CC. The accumulator is feeding all the systems of the device. The system 1, for the monitoring and detection of spatial charge accumulation, is running permanently and starts the device when the modulus of the electric field in at least two points of vertical path reaches any critical value.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
Fig. 9.5: Active lightning protection and lightning energy extraction device function 15 Probe laser 3 radiation beam 16 Bottom layer of thundery clouds 17 Reflected probe laser 3 radiation 18 Critical space charge density 19 Laser 2 radiation beam 20 Lightning channel 21 Mirror protection laminar air jet When the modulus of electric field reaches the critical value, the system for static control of electric field intensity in air 1 send a start signal to the control system CS, which starts all the systems of device. As source for scanning the atmosphere can be used a CO2 laser 3 with polarized beam. The beams of the two lasers 2 and 3 must be closed each to other and parallel. The laser 3 runs periodically all the time and the laser 2 emits a pulse only when the signal from CS is received. The beam 15 of laser 3, entering the through the bottom layer 16 of thunder clouds, is reflected by them and scattered. The moving mirror 4 directs the beam 15 to scan an enough large surface of the clouds in short time. When the optical receiver 5 with Polari scope detects a critical modification of the reflected beam polarization due to electric field it sends a signal to CS, which starts the laser 2 and stops the mirror for a short time, enough long for laser pulse generation. As a result, the pulse beam 19 is directed by the stopped mirror in the same direction, when the strong electric field was detected (18). The optical spark generated by the beam 19 initiates a streamer followed by leader between the charge concentration and the top of the metallic tube 6. The surge current 20 follows the circuit: earth, metallic coating 8, metallic tube 6, leader channel, the cloud 16. This surge current produces damped oscillations in the LC tank formed by the capacitance C between the coating 8 and the metallic cylinder 6 and the inductance L of the ABSTRACT - 34 -
RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE primary winding of parallel connected transformer T. The induced in secondary winding of T voltage is rectified by the full-wave rectifier 12 and used to charge almost instantly the condenser 13. The accumulated in the condenser energy is converted by CC and used to charge the accumulator battery for PDU and others consumers feeding. The capacitance C between the coating 8 and the metallic cylinder 6 can be easy evaluated as follows: 2 εεπ l C ≈ 0 r + 2 dD (9.3) ln D
9.4. Conclusions 1. The experiences show that the laser spark can replace a metallic rod for the orientation of lightning stroke and the use of this technique can reduce two and more times the probability of protected object damage. 2. Electric field intensity monitoring should be made not in bottom layer of thunder clouds, but in the vicinity of grounded electrode. This is simpler and more efficient. 3. The electric field near the top end of the protection electrode can be evaluated measuring the accumulated on the upper part of the grounded cylinder.
After analyzing the obtained results, we drew some final conclusions, we scored main personal contributions in this paper and have revealed the usefulness of the thesis and these are systematized in Chapter 10, entitled "Conclusions and personal contributions. Future research directions". Also in this chapter we have presented some future research directions. In the Annex of this thesis are some theoretical concepts related to fiber optic data transmission, with reference to the presentations made especially in Chapters 6 and 7. The main objective of the thesis is to make several original contributions in research and establish the causes of fire in general and the electrical nature of fire’s causes in particular, to reduce errors in exact determination of the fire’s causes and circumstances determining what led to the production and development of fire, this is thoroughly technically and theoretically analyzed through detailed physical and chemical phenomena researching accompanying combustion process and its initiation especially. Specific objectives include making research to discover ways to minimize the risk of electrical nature fire’s causes, few of these being as follows: ¾ The achievement of statistical comparative analysis based on fire ignition sources such as electricity in four different countries and highlighting the relatively high percentage of electrical nature fire’s causes in our country compared to the other surveyed countries; ¾ Determining the ampacity of insulated conductors in conduit using the original formula, based on analysis of data extracted from tables presented in normative for the design and execution of electrical installations with voltages up to 1000 V a.c. and 1500 V c.c. - I7- 2002 and interpolate these values, this formula for determining the fast maximum allowable current, and thus the minimum section of the conductors can be used in current research activities of the fire’s causes and, last but not least, to check specific projects for realization of transport installation and electrical power supply; ¾ The use of the theoretical model of heat diffusion field in one, two and three-dimensional half space propagation examining how thermal field is propagating in homogeneous space for solving inverse problems regarding establishing the fire’s causes, the place of their initial and circumstances determining the evolution and spread of fire in space, by using these models can more accurately determine the causes of fire, and by disseminating information to those involved in the use of transport facilities and electrical power supply, will increase the default degree of prevention and reduction of electricity fires occurrence risk;
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE ¾ Bringing to the forefront of several innovations in the field, making some remarks about the modern detection systems and signaling facilities, we presented an analysis of fire detectors, the development of a fire and detection opportunity and tried raising awareness for decision factors to obtain a greater openness in terms of increased investment in these systems, which, once implemented, serving to significantly reduce the number of fires and damage caused by them. Also, we present in detail the operation of smoke exhaust detection systems and benefits of these systems; ¾ Also to minimize the risk of electrical nature fire’s causes, regarding lightning protection using laser induced spark, we analyzed a patent on the active lightning energy extraction device and we revealed the use of laser spark directing strike lightning to the lowering elements in order to increase the degree of insurance of protected objects and reducing the number of fires and damage caused by them; ¾ Stimulating the interest of decision makers in institutions and economic objectives concerning analyzing in detail the possibility of data transmission systems using optical fiber in the detection and signaling systems and building management to achieve from point of view of defense against fire.
10. Final conclusions and personal contributions. Future research directions
After analyzing the results, presented in this thesis, which are combined with all actual research, on the field, of fires due to electrical causes, in which I participated as an investigator, we draw some conclusions, some of them being measures to be taken in order to minimize the risk of fire due to electrical causes, as well as reducing the number of victims and damages, as follows: a. if we determine precisely the causes which lead to electrical fires, will not put on false tracks preventive inspection and lead to the improvement of security systems, transport and electricity supply and their greater safety in use; b. insisting on an increase in the protection of transport systems and power supply, default rate of fires due to electrical causes will decrease, that in our country means 24% of the total number of fires [84]; c. once the rate of fires due to electrical causes decreases, will decrease and the number of victims found in these as well as the value of property damage; d. another cause of the relatively large number of fires due to electrical causes is the lack of education in the field and lack of public awareness; this occurs due to the limited number of existing coercive actions, to provide a lever to determine each individual's awareness and compliance the risks they are exposed violating these rules; in this respect such leverage could be, concluding insurance policies, to order the execution of periodic inspections by qualified persons; e. insisting on workers awareness on compliance during operation of transport systems and power supply, the debate during regular briefings regarding health and safety of such rules, will lead to greater safety in operation and lower default rates of fires due to electrical causes.
The main personal contributions in the present thesis, largely arising from the execution of research experience and establish the causes of fire, in conjunction with the results of research conducted under the guidance and coordination of Prof. Phd. Grigore Cividjian, we can bring up the following: a. analyzing situations in researching the causes of fire and allocation with ease with of a false fire causes; perform comparative statistical analysis of such electrical fire in four different states and collating data regarding Romania's position in this comparative analysis;
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE b. establishment and interpretation of indicators to achieve a comparative analysis of fire statistics in the countries debated; c. develop a rapid method for determining the original section of the minimum allowable cable with several isolated conductors or a single insulated conductor, protected by protective tubes buried in a thermally insulated wall; In this context it is proposed an original formulafor calculating maximum allowable current in the conductors of the cables, followed by interpretation of results obtained by the difference formula and the data contained in I7-2002 tables; Mentioned is a comparison of calculation of the allowable minimum section several conductors insulated cables or a single insulated conductor, using I7 – 2002 and I7-2009; d. research of the thermal diffusion field in a one, two, and three-dimensional homogeneous half space and presenting results in a suitable synthetic form to solve a practical operational problem locating the place of fire initiation; suggesting a method for identifying auxiliary fire causes based on solving inverse problems of thermal field diffusion in homogeneous isotropic medium with equivalent parameters; presentation of examples of solving inverse problems based on the analysis and presentation of proper uniform thermal field propagation in homogeneous environments; e. centralization of the detection systems concepts and their implementation to achieve intelligent building management in terms of defense against fire; f. analysis of the results of recent theoretical and experimental use of laser spark for stimulating and guiding lightning, with the aim of raising the level of lightning protection of very important objectives; g. analyzing the operation of the "active lightning with starting device”, study associated physical phenomena and present a critical analysis to these lightning protection systems; h. analysis of a recently patented device for laser active protection to atmospheric surge with energy recovery; i. suggesting advantages posed by introducing the use of fiber optic data transmission in fire protection and presentation of the main elements to take into account the transmission of data through optical fiber; j. in view of the analyzed and discussed in this thesis, whether these elements should be some ways to minimize the risk of fire in general, and fire due to electrical causes especially, would be presented and implemented to professional structures for preventing and investigating the causes of fire in the emergency inspectorates, we consider that errors made in determining the causes of fire would be much reduced and therefore the number of such events would decrease significantly.
Future research directions
¾ research in practical terms of the behavior of conductors chosen based on measurements using the original formula proposed to determine the maximum allowable current, verify its viability and with the degree of deviation acceptance, widespread implementation; ¾ further research on the functioning of the lightning striking, the boot device and how the occurrence of the back stroke, taking into account the fact that the height of the starting orientation of lightning is rather related to the generation of back stroke than the electric field irregularities in the cloud thunderstorms; ¾ further research regarding the use of laser induced spark to guide lightning strikes; ¾ Research how to implement the use of optic fiber data transmission systems and fire alarm detection as well as management of intelligent buildings in terms of defense against fire, taking into account the advantages to conventional technologies afforded them protection against fire, especially in terms of external interference immunity, the balance of power and the appearance of aging.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
References
[1] Aleksandrov, N.L., Bazelyan, E.M., Carpenter, R.B., Jr., Drabkin M.M., Raizer Yu.P. The effect of coronae on leader initiation and development under thunderstorm conditions and in long air gaps/ J. Phys. D: Appl. Phys. 2001, V. 34, p. 3256-3266. [2] Aleksandrov, N.L., Bazelyan, E.M., D’Alesasandro, F.and Raizer, Yu.P. Dependence of lightning rod efficacy on its geometric dimension – computer simulation/ J. Phys. D: Appl. Phys. 2005, V. 38, p. 1-14. [3] Apollonov, V.V., Baitsur, G.G., Ermchenco, A.V., et al., High-Power Molecular Lasers Pumped by a Volume Self-Sustained Discharge, J. Opt. Soc. Am., 1991, vol. 8, no. 2, p. 220. [4] Asandei, D., Protecţia sistemelor electrice, Editura Matrix Rom, Bucureşti, 1999. [5] Asinovskii, E.I., Vasilyak, L.M., and Nesterkin, O.P., Teplofiz. Vys. Temp., 1997, vol. 35, no. 6, p. 858 (High Temp. (Engl. transl.), vol. 35, no. 6, p. 845). [6] Badea, I., Protecţia prin relee şi automatizarea sistemelor electrice, Editura Tehnică, Bucureşti, 1973. [7] Bateman, H., Erdélyi, A., Tables of integral transforms I, Mc Graw-Hill, N. Y. 1954. [8] Bates, Regis J. (2001). Optical Switching and Networking Handbook. New York: McGraw-Hill. [9] Bazelyan, E.M. and Raizer, Yu.P., Usp. Fiz. Nauk, 2000, vol. 170, no. 7, p. 753. [10] Bazelyan, M., Raizer, Yu.P., Lightning attraction mechanism and the problem of lightning initiation by lasers, Uspehi, 170 (2000), nr. 7, 753-769. [11] Bălulescu, P., Cauzele tehnice ale incendiilor şi prevenirea lor, Editura tehnică Bucureşti 1971. [12] Bălulescu, P., Măcriş, V., Prevenirea incendiilor, Editura Tehnică, Bucureşti – 1962. [13] Biran, A., Breiner, M., Matlab for Engineers, Addison – Wesley Publishing Company, Great Britain, 1996. [14] Boroi, A. şi NISTOREANU, Gh., Drept penal şi drept procesual penal, Curs selectiv, Editura All Beck, Bucureşti 2005. [15] Broscăreanu, D. and Cividjian, G. A., On the ampacity of insulated conductors in conduit – 10th International Conference on Applied and Theoretical Electricity ICATE 2010, Craiova, October 8-9; ISSN 2026-0150. [16] Broscăreanu, D. şi Cornea, N., Sisteme de protecţie (paratrăsnete) active – Buletinul de Informare şi Documentare nr. 3(98) din 2010, Anul XIX, ISSN 2065-9318, p. 609- 617. [17] Carslaw, H. S., Jaeger, J. C., Conduction of heat in solids, 2-nd ed., Oxford. [18] Călin, S., Marcu, S., Protecţia prin relee a sistemelor electrice, Editura Tehnică, Bucureşti, 1975. [19] Cira, O., Lecţii de Mathcad 2001 Professional, Editura Albastră, Cluj-Napoca, 2006. [20] Cividjian, G.A., Aparate Electrice vol. 1, Universitatea din Craiova, 1979. [21] Cividjian, G. A., Aparate electrice – Note de curs, Universitatea din Craiova, 1979, [22] Cividjian, G.A., Aparate electrice.Izolaţie şi arc. Editura Avrămeanca. Craiova, 1996. [23] Cividjian, G. A., Broscăreanu, D. and Popa, D., On laser spark aided lightning protection - 10th International Conference on Applied and Theoretical Electricity ICATE 2010, Craiova, October 8-9; ISSN 2026-0150. [24] Cividjian, G.A., Broscăreanu, D., Thermal field propagation in one, two and three- dimensional half space, XI-th International Workshop on Optimization and Inverse Problems in Electromagnetism September 14 – 18, 2010, Sofia, Bulgaria. [25] Cividjian, G.A., Cividjian, A.G., Modeles statistiques et fiabilite – pour les etudiants des facultes techniques, Universitatea din Craiova – 2003.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE [26] Constantinescu R., Platon, M. – Utilizarea maselor plastice în construcţii, Editura tehnică, Bucureşti, 1985. [27] Crăciun, I., Calotă , S., Lencu, V. – Stabilirea şi prevenirea cauzelor de incendiu, Ediţia a-2-a, Editura Tehnică, Bucureşti 1999. [28] Deich, M.E. and Filippov, G.A., Gazodinamika dvukhfaznykh sred (Gas Dynamics of Two-Phase Media), Moscow: Energiya, 1968. [29] Doicaru, E. şi Maria, M., Optoelectronică. Lucrări practice, Editura Reprograph – Craiova, 2010. [30] Drăgan, G., – Tehnica tensiunilor înalte, Volumul I, Ed. Tehnică, Bucureşti, 1996. [31] Flucuş I. – Comportarea şi protecţia la foc a construcţiilor şi instalaţiilor, note de curs, Facultatea de Pompieri, Bucureşti, 1995. [32] Flucuş I., Popescu G., Şerban M. – Principalele acte normative din domeniul apărării împotriva incendiilor şi conexe cu acestea, Editura PRINTEH, Bucureşti, 2001. [33] Fris, S. E., Timoreva, A. V., (1965). Curs de fizica generala – Optică , Fizica atomica (vol. 3) Bucureşti- Editura Tehnică. [34] Glasesmenn, G. S. (1999). "Advancements in Mechanical Strength and Reliability of Optical Fibers". Proc. SPIE CR73: 1. [35] Hecht, Jeff (1999). City of Light, The Story of Fiber Optics. New York: Oxford University Press. p. 114. ISBN 0195108183. [36] Hortopan, Gh., Aparate electrice de comutaţie, Vol. I, Editura Tehnică. [37] Hussein bin Ahmad, Study on the early streamer emission mechanisms aided by laser radiation ionization process, Universiti Teknologi Malaysia, 2007. [38] IEC Standard 1024-1, 1990. Protection of Structures Against Lightning. Part 1. General Principals. [39] IEC Standard 1312-1, 1994. Protection Against Lightning Electromagnetic Impulse (LEMP). Part 1. General Principals. [40] IEC Standard, Publication 60364-5-52, Electrical installations of buildings – Part 5- 52: Selection and erection of electrical equipment – Wiring systems, ediţia a II-a 2001- 08. [41] Ionescu C., Homeag I. - Sisteme de supraveghere şi alarmare la incendii – a X-a conferinţă a Facultăţii de Instalaţii, noiembrie 2003. [42] Kadzov, G.D. and Rezunkov Yu., A., Promising Techniques of Increase Reliability in a Lightning Protection System, Proc. 24th Int. Conf. on Lightning Protection, Birmingham, 1998, vol. 1, p. 468. [43] Krylov, V. I., Skoblya, N. S., Handbook for numerical inverse Laplace transform (In Russian: В. И. Крылов, Н. С. Скобля, Справочная книга по численному обращению преобразования Лапласа ), Nauka i tehnika, Minsk, 1968. [44] Mercure, H.P., Potvin, C., Duguay, B., et al., Guiding and Triggering Large-Scale Spark Discharges Using Ultra-Short Pulse Lasers, Proc. 25th Int. Conf. on Lightning Protection, Rhodes, 2000, p. 48. [45] Miki, M., Wada, A., and Shindo, T., Fundamental Study of Laser-Triggered Lightning. Characteristics of Laser- Guided Discharges in Long Air Gaps, Proc. 23rd Int. Conf. on Lightning Protection, Firenze, 1996, vol. 1, p. 10. [46] Miki, M., Wada, A., and Shindo, T., Laser-Triggered Lightning Using an Intense UV Laser Pulse, Proc. 24th Int. Conf. on Lightning Protection, Birmingham, 1998, vol. 1, p. 451. [47] Moore, C., Aulich, G., and Rison, W. Measurement of lightning rod responses to nearby strikes. / Geophys. Res. Let. 2000, 27,P. 3201-3204. [48] Neiman, L. R., Kalantarov, P. L., Bazele fizice ale electrotehnicii, Editura Energetică de stat, 1955. [49] Oprea O. - Sisteme moderne de detectare şi semnalizare a incendiilor – lucrare de dizertaţie “Ingineria siguranţei la foc“, Facultatea de Pompieri, 2004.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE [50] Peştişanu C., Darie M., Popescu L., Voiculescu M. – Construcţii, Editura Didactică şi Pedagogică, Bucureşti, 1995. [51] Petrehus, V., Popescu, S.A., Probabilităţi şi Statistică, Universitatea Tehnică de Construcţii Bucureşti, 2005. [52] Preda, M., Cristea, P., Bazele electrotehnicii, Vol. II, Editura Didactica si Pedagogica. [53] Preda, M., Cristea, P., Manea F., Bazele electrotehnicii, Editura Didactică şi Pedagogică, Bucureşti, 1980. [54] Proca G. – Construcţii, Editura Matrix Rom, Bucureşti, 1999. [55] Rison, W., Experimental validation of conventional and non-conventional lightning protection systems. 2003. Report on Conf. IEEE. Toronto, Canada. [56] Russell, Ph. (2003). "Photonic Crystal Fibers". Science 299 (5605): 358. [57] Scheiber, E., Lixăndroiu, D. MathCAD : prezentare şi probeme rezolvate – Bucureşti: Editra Tehnică, 1994. [58] Siegel, R., Howell, J. R, Thermal radiation heat transfer, Mc-Graw-Hill, N. Y., 1972. [59] Sinkevich, O.A. and Gerasimov, D.N., Propagation of Super-High-Speed-Ionizing Waves in Long Shielded Tubes, J. Phys. D, 2000, vol. 33, no. 1, p. 54. [60] Smelkov G. I., Riabikov A. I. - „Analiza datelor statistice asupra pericolului de incendiu a articolelor electrice”, Energy-safety and energy-economy magazine, (in Russian: Энергобезопасность и энергосбережение), no. 1, 2009, ISSN 2071-2219. [61] Suciu, I. Aparate electrice, Editura Didactică şi Pedagogică, Bucureşti, 1968. [62] Şerbu, T. – Instalaţii de supraveghere la incendii, Bucureşti 1989. [63] Şerbu, T., Nicolescu, R. – Sisteme de înaltă sensibilitate pentru detecţia fumului – sesiunea de comunicări ştiinţifice a Academiei Navale Mircea cel Bătrân, Constanţa, 2002. [64] Şora, C., Bazele electrotehnicii, Editura Didactică şi Pedagogică, Bucureşti, 1982. [65] Temnikov, A.G. and Orlov, A.V., Elektrichestvo, 1996, no. 8, p. 18. [66] Timotin, A., Hortopan, V., Mastero, S., Ifrim, A. şi Preda, M., Lecţii de Bazele electrotehnicii vol. I, Ediţia 1964. [67] Vasilyak L.M., Vereshchagin, I.P, et al., Investigation of electric dischargees in the vicinity of a charged aerosol cloud and their interaction with laser-induced spark, High temperature, vol. 41, no. 2, 2003, pp. 166-175. [68] Vereshchagin, I.P., Antsupov, K.V., Bazutkin, V.V., et al., Application of Charged Aerosol Cloud for Simulation of Upward Leader Generation, Proc. 21st Int. Conf. on Lightning Protection, Berlin, 1992, p. 25. [69] Vereshchagin, I.P., Temnikov, A.G., Koshelev, M.A., and Makalsky, L.M., Determination of Electric Fields Induced by a Charged Aerosol Cloud, Proc. 9th Int. Symp. on High Voltage Engineering, Graz, 1995, p. 2165. [70] Wong, H. Y., Heat transfer for engineers, Longman, London and New York, 1977. [71] Yano, K., Tsuji, T., Otsubo, M., et al., Leader Propagation Process for Laser-Induced Discharge, 8th Asian Conf. on Electrical Discharge, Bangkok, 1996, no. 603. [72] Александров Г. Н. Молния и молмиезащита (Lightning and lightning protection), Наука, 2008. [73] Шпиганович А. Н., Свиридов П. Н. Устройство активной молниезащиты и отбора энергии молнии (Active lightning protection and lightning energy extraction device), Pat. RU2277744, 2004. [74] *** "1971-1985 Continuing the Tradition". GE Innovation Timeline. General Electric Company. http://www.ge.com/innovation/timeline/index.html. Retrieved 2008-10-22. [75] *** Annals of the University of Craiova, Electrical Engineering series, No. 34, 2010; ISSN 1842-4805, p.148-155. [76] *** Codul de procedură penală-ediţie oficială, Editura All Beck, Bucureşti 2003. [77] *** Curs de optică. Diamond the fiber meeting. http://www.diamond- fo.ro/index.php?page=home.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE [78] *** Department for Communities and Local Government: London - „Fire Statistics, United Kingdom, 2007” – August 2009. [79] *** French Standard NF C 17 – 102 July 1995 – Lightning protection. Protection of structures and open areas against lightning using early streamer emission air terminals. [80] *** http://aparate.elth.ucv.ro/index.php?path=Cividjian/. [81] *** http://eu.sabotage.org/www/ITU/G/G0671e.pdf. [82] *** http://grouper.ieee.org/groups/1394/b/old/jp971027-1394b.pdf. [83] *** http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html. [84] *** http://www.igsu.ro/documente/analiza_statistica_2007.pdf. [85] *** http://www.opsi.gov.uk/legislation/wales/wsi2007/wsi_20071075_en_1. [86] *** http://www.scritube.com/tehnica-mecanica/VERIFICAREA-LEGILOR- REFLEXIEI -103219912.php. [87] *** International Fire and Security News, 2004 – 2005. http://journalseek.net/cgi- bin/journalseek/journalsearch.cgi?field=issn&query=0961-3730. [88] *** Legislaţie privind calitatea în construcţii, Editura Matrix Rom, 1999. [89] *** Manual privind exemplificări, detalieri şi soluţii de aplicare a prevederilor normativului P-118/1999 „Siguranţa la foc a construcţiilor”, indicativ MP-008/2000. [90] *** NFPA Fire Analysis and Research, Quincy, MA - „Fire Loss in the U.S 2007 – Full Report, 8/08”. [91] *** NFPA, Fire Analysis and Research, Quincy, MA - „Large-Loss Fires-2007, 11/08”. [92] *** Normativ de siguranţă la foc a construcţiilor P118-99. [93] *** Normativ pentru proiectarea şi executarea instalaţiilor electrice cu tensiuni până la 1000 v c.a. şi 1500 v c.c., I7-2002. [94] *** Normativ privind protecţia construcţiilor împotriva trăsnetului M.L.P.A.T. 48/N/30.06.2000 - B.C. nr. 2/2001 Broşura ICECON - Indicativ: I 20-2000. [95] *** Normativ pentru proiectarea şi executarea instalaţiilor interioare de semnalizare a incendiilor şi a sistemelor de alarmare contra efracţiei din cladiri M.L.P.A.T.- Indicativ: I 18/2-02. [96] *** Optical Fiber. Sendai New. http://www.city.sendai.jp/soumu/kouhou/s-new- e6/page01.html. Retrieved April 5, 2009. [97] *** Reglementări privind apărarea împotriva incendiilor – Editura Universitas Company S.A., Bucureşti, 1999. [98] *** http://www.proenerg.ro/jpg/materials/Pliant%20Prevectron.pdf. [99] *** http://www.echipot.ro/paratrasnete/ipt-cu-paratrasnet-ioniflash/paratrasnete- ioniflash_7_17_18.html. [100] *** http://www.echipot.ro/downloads/pdf/Brosura_IONIFLASH_Benjamin.pdf. [101] *** http://www.paratrasnete-pda.ro/produse/paratrasnet_DAT.htm.
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE
CURRICULUM VITAE
BROSCĂREANU DUMITRU
Workplace: Inspectorate for Emergency Situations "General Magheru" Vîlcea County, Organizational Management Occupation: Specialist officer Address: Nicolae Titulescu Street, no.14, bl.H6, Sc.D, ap.6, Rîmnicu Vîlcea, România Tel.: +(4) 0350 402547 (home),+(4) 0741212322 (mobile) +(4) 0250 748201(work) E-mail: [email protected] Date of birth: July 14, 1974 Civil status: Married, one child Nationality: Romanian Training: Engineer, Technical University of Construction Bucharest, Faculty of Systems, July 1997 Nr.205/I/8 degree. Training courses: • 4 to 8 March 2002, specializing in research into the causes of fire, the Center for Studies, Experiments and Specialization PSI, Bucharest. • 6 months postgraduate training in the specialty "Fire safety of buildings and facilities" Technical University of Construction Bucharest, 2003. • June 6-July 3, 2007, qualification for occupation "technical framework with responsibilities in preventing and fighting fires," COR code 516 106, Rm Vîlcea. Foreign languages: English - reading, technical translation French - reading, technical translation Professional experience: August 1997 - March 2000, deputy company commander in Fire Company Victoria, Fire Group "Ţara Bârsei" Braşov County; April 2000 - December 2001, deputy commander of the detachment to Fire Detachment Rm Vîlcea, Fire Group "General Magheru" Vîlcea County; December 2001 - December 2004, specialist officer, Fire Group "General Magheru" Vîlcea County; December 2004 to the present, specialist officer in the Inspectorate for Emergency Situations "General Magheru" Vîlcea County. Scientific experience: 4 scientific papers published:
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RESEARCHING AND ESTABLISHING THE CAUSES OF ELECTRICAL NATURE FIRES AND MEASURES TO MINIMIZE THE RISK OF FIRE OCCURRENCE • Broscareanu, D. and Cividjian, G. A., On the ampacity of insulated conductors in conduit – 10th International Conference on Applied and Theoretical Electricity ICATE 2010, Craiova, October 8-9; ISSN 2026-0150; • Cividjian, G. A., Broscareanu, D. and Popa, D., On laser spark aided lightning protection - 10th International Conference on Applied and Theoretical Electricity ICATE 2010, Craiova, October 8-9; ISSN 2026-0150; • Cividjian, G. A. and Broscareanu, D., Thermal field propagation in one, two and three-dimensional half space - XI-th International Workshop on Optimization and Inverse Problems in Electromagnetism September 14 – 18, 2010, Sofia, Bulgaria; • Broscareanu, D. and Cornea, N., Protection systems (lightning) active - Documentation and Information Bulletin no. 3 (98) in 2010, Year XIX, ISSN 2065-9318, p. 609-617;
Domains of responsibility: 1. Research and establishing the causes of fire and determining the circumstances; 2. Coordination of the actions of fire-fighting intervention; 3. Organization and planning of the main tasks and activities; 4. Deployment of tactical exercises and applications; 5. Specific carrying out regular inspection within the competence.
Competence in informatics • Operating systems: WINDOWS; • Programming languages: VISUAL BASIC; • Word processors: MICROSOFT OFFICE - WORD; • Application software: MATHCAD, AUTOCAD .
Other matters considered relevant Managerial experience • Head compartment Organizational Management, Mission Planning and Resources, December 2004 - June 2011; • Head compartment and Complete Resource Organization in Exceptional Circumstances, in June 2011 to the present. Professional experience • Designated specialist officer for research and establishing the causes of fire, in December 2001 to the present.
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