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P L I Skelton - One of the best experts on this subject based on the ideXlab platform.
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Simulation of wet-snow accretion by axial growth on a transmission Line Conductor
Applied Mathematical Modelling, 1995Co-Authors: G Poots, P L I SkeltonAbstract:When a snowflake, at air temperature just above the freezing point, impacts on a Conductor, it fragments such that some of the mass adheres forming a snow deposit, and the remainder ricochets into the air stream. Thus the theoretical prediction of the shape of this accreting surface, evolving on the windward side of the Conductor, crucially depends on the postulation of a law concerning the rate of adhesion or accretion during snowflake bombardment. Knowledge of the shape of the surface is, of course, required to evaluate lift, drag, and moment coefficients to be used in the study of the aeroelastic stability of the snow/Conductor system. On simulation of the accretion process using a cosine law, the nonLinear snow evolution equation is formulated and solved by analytical and numerical techniques. The predicted snow shapes are found to be in excellent agreement with field observations on natural snow shapes.
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Further aspects of dynamical models for rime‐ice and snow accretion on an overhead Line Conductor
International Journal for Numerical Methods in Engineering, 1994Co-Authors: G Poots, P L I SkeltonAbstract:Current three-dimensional, time-dependent mathematical models for (dry) rime-ice and snow accretion on Overhead Line Conductors (OHLC), of finite span and finite torsional stiffness, assume that the airflow past the iced OHLC is given by Attached Potential Flow (APF) and that the effect of aerodynamic moment on the rotation of the OHLC during ice evolution can be neglected. In the present numerical study a CFD code is employed to simulate the turbulent airflow past an iced OHLC and used to validate APF predictions for icing particle impactions, ice evolution and rotation of the OHLC. Comparisons are made for the following: (a) icing particle impaction velocities determined using the CFD code and APF when, for example, the iced surface is fixed at an attitude experiencing lift; (b) the aerodynamic moment, for a chosen ice shape at a range of attitudes, predicted using the CFD code and AFT; (c) the aerodynamic moment, for natural ice shapes, given by APF and measured in wind-tunnel tests; (d) the effect of aerodynamic moment, predicted using the CFD code and APF, on ice evolution during a short period of icing. Finally, on employing aerodynamic moments calculated using APF modified values, the sensitivity of the ice-accretion process, across the span of the OHLC, to Conductor rotation and various meteorological and physical data for the icing particles is discussed.
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Theoretical aspects of iceload measurements on fixed rods and overhead Line Conductors: A transfer function for dry rime-ice accretion
Atmospheric Environment. Part A. General Topics, 1993Co-Authors: I.p. Bibby, G Poots, P L I SkeltonAbstract:Abstract This paper is concerned with theoretical aspects of the methodology of iceload measurements on an overhead Line Conductor (OHLC) of finite span and finite torsional stiffness. The purpose is to establish the relationships between the iceload on a fixed rod or sampler and the spatial average iceload on an OHLC. A theoretical database, generated using dynamical models for rime-ice accretion on Conductors, is carefully analysed to express iceload data as a function of meteorological conditions and the mechanical properties of the OHLC. These results provide the required ratios of the iceload on a sampler to that on OHLCs as a function of time during an icing incident. A transfer function, relating theoretically predicted iceloads on an OHLC to that for a sampler, is then constructed and should prove useful in the development of the corresponding methodology for relating sets of field measurements in this way. For design purposes progress in the latter is desirable.
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rime and glaze ice accretion due to freezing rain falling vertically on a horizontal thermally insulated overhead Line Conductor
International Journal of Heat and Fluid Flow, 1992Co-Authors: G Poots, P L I SkeltonAbstract:A theory of atmospheric icing due to freezing rain on an overhead Line Conductor (OHLC) is developed. The rain falls vertically on a horizontal OHLC that is thermally insulated. It is assumed that the collection efficiency of the accretion surface is unity and that this surface is in thermodynamic equilibrium with the environment. For air temperature TA ⩽ 0°C and raindrop temperature TD ⩽ 0°C, the freezing rain accretes as rime ice, provided that the temperature of the ice surface Tl < 0°C. The evolution equation governing the mass transfer at the accretion surface is solved analytically, yielding the shape of the rime-ice surface. Equations governing the thermal state of the rime-ice deposit are also given. These determine the onset of wet growth or glaze accretion at the upper stagnation Line during suitable environmental conditions. For environmental conditions producing an ice surface at temperature Tl = 0°gC, the freezing accretes as glaze. Equations governing the heat and mass transfer at the surface determine the shape of the glaze surface and the downward viscous motion of the unfrozen water. For TD < 0°C, glaze evolution equations are developed for TA ⩽ 0°C and TA 0°C. Analytical solutions of these equations are obtained. In particular, when TD < −TA < 0°C, the evolution equation predicts a novel limiting growth that is triangular in shape. Further study of the mass and heat transfer conditions, in the neighborhood of this final stage of glaze accretion, shows that it is maintained in thermodynamic equilibrium with its warm air environment.
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Snow accretion on overhead Line Conductors of finite torsional stiffness
Cold Regions Science and Technology, 1991Co-Authors: P L I Skelton, G PootsAbstract:Abstract A theoretical study of snow loading on the windward side of an overhead Line Conductor (OHL), of finite span and finite torsional stiffness, is made on employing known meteorological data for dendritic snowflakes to determine their winddriven migration in the vicinity of the Conductor and their impaction on the Conductor. Two different three-dimensional, time-dependent mathematical/computer models are developed which are capable of simulating a wide variety of environmental conditions known to exist in a snow storm. The numerical results of the complete spectrum of snowflakes model (CSM) are used to check the accuracy of those results obtained from an average snowflake size model (ASM). It is shown that predictions of the considerably less computationally demanding ASM are in almost exact agreement with those of CSM.
G Poots - One of the best experts on this subject based on the ideXlab platform.
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Simulation of wet-snow accretion by axial growth on a transmission Line Conductor
Applied Mathematical Modelling, 1995Co-Authors: G Poots, P L I SkeltonAbstract:When a snowflake, at air temperature just above the freezing point, impacts on a Conductor, it fragments such that some of the mass adheres forming a snow deposit, and the remainder ricochets into the air stream. Thus the theoretical prediction of the shape of this accreting surface, evolving on the windward side of the Conductor, crucially depends on the postulation of a law concerning the rate of adhesion or accretion during snowflake bombardment. Knowledge of the shape of the surface is, of course, required to evaluate lift, drag, and moment coefficients to be used in the study of the aeroelastic stability of the snow/Conductor system. On simulation of the accretion process using a cosine law, the nonLinear snow evolution equation is formulated and solved by analytical and numerical techniques. The predicted snow shapes are found to be in excellent agreement with field observations on natural snow shapes.
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Further aspects of dynamical models for rime‐ice and snow accretion on an overhead Line Conductor
International Journal for Numerical Methods in Engineering, 1994Co-Authors: G Poots, P L I SkeltonAbstract:Current three-dimensional, time-dependent mathematical models for (dry) rime-ice and snow accretion on Overhead Line Conductors (OHLC), of finite span and finite torsional stiffness, assume that the airflow past the iced OHLC is given by Attached Potential Flow (APF) and that the effect of aerodynamic moment on the rotation of the OHLC during ice evolution can be neglected. In the present numerical study a CFD code is employed to simulate the turbulent airflow past an iced OHLC and used to validate APF predictions for icing particle impactions, ice evolution and rotation of the OHLC. Comparisons are made for the following: (a) icing particle impaction velocities determined using the CFD code and APF when, for example, the iced surface is fixed at an attitude experiencing lift; (b) the aerodynamic moment, for a chosen ice shape at a range of attitudes, predicted using the CFD code and AFT; (c) the aerodynamic moment, for natural ice shapes, given by APF and measured in wind-tunnel tests; (d) the effect of aerodynamic moment, predicted using the CFD code and APF, on ice evolution during a short period of icing. Finally, on employing aerodynamic moments calculated using APF modified values, the sensitivity of the ice-accretion process, across the span of the OHLC, to Conductor rotation and various meteorological and physical data for the icing particles is discussed.
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Theoretical aspects of iceload measurements on fixed rods and overhead Line Conductors: A transfer function for dry rime-ice accretion
Atmospheric Environment. Part A. General Topics, 1993Co-Authors: I.p. Bibby, G Poots, P L I SkeltonAbstract:Abstract This paper is concerned with theoretical aspects of the methodology of iceload measurements on an overhead Line Conductor (OHLC) of finite span and finite torsional stiffness. The purpose is to establish the relationships between the iceload on a fixed rod or sampler and the spatial average iceload on an OHLC. A theoretical database, generated using dynamical models for rime-ice accretion on Conductors, is carefully analysed to express iceload data as a function of meteorological conditions and the mechanical properties of the OHLC. These results provide the required ratios of the iceload on a sampler to that on OHLCs as a function of time during an icing incident. A transfer function, relating theoretically predicted iceloads on an OHLC to that for a sampler, is then constructed and should prove useful in the development of the corresponding methodology for relating sets of field measurements in this way. For design purposes progress in the latter is desirable.
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rime and glaze ice accretion due to freezing rain falling vertically on a horizontal thermally insulated overhead Line Conductor
International Journal of Heat and Fluid Flow, 1992Co-Authors: G Poots, P L I SkeltonAbstract:A theory of atmospheric icing due to freezing rain on an overhead Line Conductor (OHLC) is developed. The rain falls vertically on a horizontal OHLC that is thermally insulated. It is assumed that the collection efficiency of the accretion surface is unity and that this surface is in thermodynamic equilibrium with the environment. For air temperature TA ⩽ 0°C and raindrop temperature TD ⩽ 0°C, the freezing rain accretes as rime ice, provided that the temperature of the ice surface Tl < 0°C. The evolution equation governing the mass transfer at the accretion surface is solved analytically, yielding the shape of the rime-ice surface. Equations governing the thermal state of the rime-ice deposit are also given. These determine the onset of wet growth or glaze accretion at the upper stagnation Line during suitable environmental conditions. For environmental conditions producing an ice surface at temperature Tl = 0°gC, the freezing accretes as glaze. Equations governing the heat and mass transfer at the surface determine the shape of the glaze surface and the downward viscous motion of the unfrozen water. For TD < 0°C, glaze evolution equations are developed for TA ⩽ 0°C and TA 0°C. Analytical solutions of these equations are obtained. In particular, when TD < −TA < 0°C, the evolution equation predicts a novel limiting growth that is triangular in shape. Further study of the mass and heat transfer conditions, in the neighborhood of this final stage of glaze accretion, shows that it is maintained in thermodynamic equilibrium with its warm air environment.
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Snow accretion on overhead Line Conductors of finite torsional stiffness
Cold Regions Science and Technology, 1991Co-Authors: P L I Skelton, G PootsAbstract:Abstract A theoretical study of snow loading on the windward side of an overhead Line Conductor (OHL), of finite span and finite torsional stiffness, is made on employing known meteorological data for dendritic snowflakes to determine their winddriven migration in the vicinity of the Conductor and their impaction on the Conductor. Two different three-dimensional, time-dependent mathematical/computer models are developed which are capable of simulating a wide variety of environmental conditions known to exist in a snow storm. The numerical results of the complete spectrum of snowflakes model (CSM) are used to check the accuracy of those results obtained from an average snowflake size model (ASM). It is shown that predictions of the considerably less computationally demanding ASM are in almost exact agreement with those of CSM.
Xinbo Huang - One of the best experts on this subject based on the ideXlab platform.
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A new on-Line monitoring technology of transmission Line Conductor icing
2012 IEEE International Conference on Condition Monitoring and Diagnosis, 2012Co-Authors: Xinbo Huang, Xu WeiAbstract:The shortage of the existing on-Line monitoring technology of transmission Line Conductor icing at home and abroad was analyzed, and the necessity of improving the existing icing monitoring technology was pointed out in this paper. The new on-Line monitoring system of transmission Line Conductor icing was designed. The master-slave monitoring structure was used in the whole system design. In this paper, the new system structure and technical features were briefly described, a new mechanical model of computing icing coating was built, and the calculation method of Conductor icing density and type was given in details. The testing and running results show that the shortage of existing on-Line monitor technology of transmission Line Conductor icing can be improved by this new on-Line monitoring technology what is more effective to guide the icing transmission Lines de-icing.
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An On-Line Monitoring System of Transmission Line Conductor De-icing
2008 3rd IEEE Conference on Industrial Electronics and Applications, 2008Co-Authors: Xinbo Huang, Qindong Sun, Jianguo DingAbstract:An on-Line monitoring system of transmission Line Conductor de-icing based on GSM SMS and Zigbee is firstly designed and produced, the composition and the technical features of which are described. The meteorology such as the temperature, the humidity, the wind speed, the rain and snow, and the air pressure etc., the icing status of transmission Lines such as the gravity of iced Conductors, the deflection angel of insulators, the deviation angel of insulators for wind, gallop frequency of Conductors etc., and the temperature of running Conductors are measured by the system, by which the study on the de-icing properties and the temperature rising properties can be made. The beginning, the process and the effect of de-icing can be controlled automatically.
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Theoretical analysis on transmission Line Conductor icing and design of on-Line monitoring system
2006 China International Conference on Electricity Distribution (CICED 2006), 2006Co-Authors: Xinbo Huang, Qindong Sun, Ronggui Cheng, Jiabing LiuAbstract:The on-Line monitoring system for transmission Line Conductor icing and galloping is developed based on GSM SMS, the theoretical computation model of icing coating and radian variation of Conductors is built, and the installation construction of force sensors is shown in figure. The running results show that the on-Line monitoring unit placed on every transmission Line tower timely measures the tower force, the deviation angel of insulators for wind, the deflection angel of insulators, the environmental temperature, the environmental humidity, the wind velocity and the wind direction etc. and sends the above information to the municipal monitoring and controlling center by SMS. The Conductor icing and galloping is computed based on the theoretical computation model built firstly, the alarm message of clearing Conductor icing is sent out on time, and the safe operation of transmission Line is effectively guaranteed. (6 pages)
Qindong Sun - One of the best experts on this subject based on the ideXlab platform.
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An On-Line Monitoring System of Transmission Line Conductor De-icing
2008 3rd IEEE Conference on Industrial Electronics and Applications, 2008Co-Authors: Xinbo Huang, Qindong Sun, Jianguo DingAbstract:An on-Line monitoring system of transmission Line Conductor de-icing based on GSM SMS and Zigbee is firstly designed and produced, the composition and the technical features of which are described. The meteorology such as the temperature, the humidity, the wind speed, the rain and snow, and the air pressure etc., the icing status of transmission Lines such as the gravity of iced Conductors, the deflection angel of insulators, the deviation angel of insulators for wind, gallop frequency of Conductors etc., and the temperature of running Conductors are measured by the system, by which the study on the de-icing properties and the temperature rising properties can be made. The beginning, the process and the effect of de-icing can be controlled automatically.
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Theoretical analysis on transmission Line Conductor icing and design of on-Line monitoring system
2006 China International Conference on Electricity Distribution (CICED 2006), 2006Co-Authors: Xinbo Huang, Qindong Sun, Ronggui Cheng, Jiabing LiuAbstract:The on-Line monitoring system for transmission Line Conductor icing and galloping is developed based on GSM SMS, the theoretical computation model of icing coating and radian variation of Conductors is built, and the installation construction of force sensors is shown in figure. The running results show that the on-Line monitoring unit placed on every transmission Line tower timely measures the tower force, the deviation angel of insulators for wind, the deflection angel of insulators, the environmental temperature, the environmental humidity, the wind velocity and the wind direction etc. and sends the above information to the municipal monitoring and controlling center by SMS. The Conductor icing and galloping is computed based on the theoretical computation model built firstly, the alarm message of clearing Conductor icing is sent out on time, and the safe operation of transmission Line is effectively guaranteed. (6 pages)
Jianguo Ding - One of the best experts on this subject based on the ideXlab platform.
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An On-Line Monitoring System of Transmission Line Conductor De-icing
2008 3rd IEEE Conference on Industrial Electronics and Applications, 2008Co-Authors: Xinbo Huang, Qindong Sun, Jianguo DingAbstract:An on-Line monitoring system of transmission Line Conductor de-icing based on GSM SMS and Zigbee is firstly designed and produced, the composition and the technical features of which are described. The meteorology such as the temperature, the humidity, the wind speed, the rain and snow, and the air pressure etc., the icing status of transmission Lines such as the gravity of iced Conductors, the deflection angel of insulators, the deviation angel of insulators for wind, gallop frequency of Conductors etc., and the temperature of running Conductors are measured by the system, by which the study on the de-icing properties and the temperature rising properties can be made. The beginning, the process and the effect of de-icing can be controlled automatically.