Study On Model Of Ice Accretion On Rotating Cylinder And Method For Forecasting Icing Parameters During Icing On Transmission Lines

Icing is a great threat to the secure and stable operation of transmission lines. The icing accidents on transmission lines have occurred frequently in China since the fiftieth of last century. Especially at the beginning of 2008, the most serious icing disaster in the meteorologic history occurred in large areas of south China. This distaster caused great economic losses to the Sate Grid Corporation and China Southern Power Grid Corporation by the heavy damage of power system which brought great inconvenience to people's production and living. The main reasons of frequent icing accidents in our power system are as the follows: the icing problem in power systme did not get enough attention, which leads the lack of basic researches on the rule of icing; effective measures for monitoring the process of ice accretion on transmission lines is lack; the researches on emergency measures of anti-icing and de-cing is short. After the icing disaster in 2008, China has invested a great deal of manpower, material and financial resources to the researches on icing.Researches on the rule of ice accretion on transmission lines and on the effective measures for forecasting the ice accretion are of great significance for avoiding the grave icing accident by adopting reasonable measures in time. The icing parameters are the basis of the icing researcheas, but the measurement of icing parameters is a difficult problem which has not been solved yet. So the research on the forecast of icing parmaters is of important academic significance and engineering practical worthiness. The main work in this paper is as follows.Based on the principle of hydrodynamics, the paper researches the collision characteristics of supercooled droplets using the numerical calculation. The motion trails of droplets and air flow, velocity fiels of droplets and air flow, and the distribution of collision speed on icing cylinder are obtained. The paper also researches the influencing factors and their effect on collision efficiency, and research results show that the collision efficiency is a function of air speed, diameters of droplet and icing cylinder. Accord to the large number of numerical calculation results, the paper gives a new analytical formula for calculating collision efficiency, and this formula is more precise compared to others'formulas. Based on the heat balance model, the paper derives the formula for calculating freezing fraction. The paper also researches the influencing factors of freezing fraction and their influence on freezing fraction. Combining the processes of collision and freeze, the paper gives the ice accretion model for the rotating cylinder.The paper designs a rotating multi-cylinders ice collector used for forecasting icing perameters. And by changing the icing parameters such as icing duration, ambient temperature, air speed etc in multi-function artificial climate chamber, the paper conducts a good deal of experimental researches to verify the ice accretion model of roating cylinder. At the same time, the influence of icing parameters on ice amount is reasearched by simulation and experiments. The results show that the influence of icing parameters on ice amount obtained by model's simulation agrees well with that obtained by experiments.The paper builds the non-linear equation set between ice amount on rotating multi-cylinders and the icing parameters according to the model of ice accretion on rotation cylinder. And the paper proposes that using the equation set to forecasting the icing parameters according to the ice amount change on rotating multi-cylinders. This paper also improves the differential evolution algorithm and uses this algorithm to solve the equation set. The icing parameters in artifical climate chamber are forecasted by this method, the forecasted results are verified by laser particle size analyzer, anemobiagraph and thermograph. And the results show that the forecasting values agree well with the experimental values.According to the ice amount on rotating multi-cylinders, the paper forecasted the equivalent icing parameters in an icing event at Natural Icing Station on Xuefeng Mountain. And using these icing paramters, the papar evaluated the ice amount on expeirmental conductors. The comparsion of the evaluated values and the measured values show that the evaluated ones are larger than the measured ones, but in general, the evaluated ice amount can reflect the ice accretion on conductors.