Researches On Risk Calculation For Dynamic Capacity Increase Of Overhead Lines

The technology of Dynamic Capacity-Increase of overhead high voltage power transmission lines is an efficient way to increase the capacity of overhead lines without construction of new lines.Unfortunately,although the technology can increase the capacity of lines,there are some risks on overhead lines and the Capacity-Increase system which is mainly due to the errors caused by calculation.Having given that models that are widely used on engineering rely heavily on meteorological parameters,this dissertation has researches on risk evaluation for Dynamic Capacity-Increase by propose a kind of models for Dynamic Capacity-Increase of overhead high voltage power transmission lines based on transient and equivalent wind coefficient which aims at reducing the dependence of meteorological parameters,evaluating the risks and insuring the process of Dynamic Capacity-Increase systems.First of all,this dissertation have researches on the models for Dynamic Capacity-Increase systems proposed by foreign scholars,mainly focusing on IEEE model and Thermal Circuit Method and the model based on equivalent wind coefficient.When the meteorological parameters change rapidly,IEEE model has a low accuracy on calculation for line ampacity.It is the line temperature that is distributed unevenly along the lines by Thermal Circuit Method.Thermal Circuit Method measures the temperature of one point on the line by which Thermal Circuit Method obtains the whole temperature of the line.Therefore,this may causes errors.Although the model based on equivalent wind coefficient reduce the dependence of meteorological parameters,there may be many errors when the temperature and equivalent wind coefficient fluctuate significantly.Secondly,the proposed model should work together with short current forecasting because the models for risk calculation should be able to forecast the risks of Dynamic Capacity-Increase system.In order to improve the accuracy of short current forecasting,this dissertation propose a method of short current forecasting based on wavelet packet and peak-type markov chain.to evaluate the current in the future and conduct experiments to identify that the model proposed is valid.At the same time,this dissertation compared the accuracy with other two models including similar-day model improved by Fuzzy Theory and BP model based on similar day which showed that the model based on wavelet packet and peak-type markov chain could analyze data by breaking down and refactoring by which it could collect valid information and improve the accuracy.In addition,it can supply current error which can be used in the risk evaluation for Dynamic Capacity-Increase systems.Finally,this dissertation proposed a kind of models for Dynamic Capacity-Increase of overhead high voltage power transmission lines based on transient and equivalent wind coefficient.This model can reduce the dependence of meteorological parameters,simplify Dynamic Capacity-Increase system,improve the accuracy on calculation for line ampacity and evaluate the risks of Dynamic Capacity-Increase systems more accurately and safely.In addition,it is proved that the errors caused by short current forecasting may have an influence on the proposed model when it works.If the result of current forecasting is not accurate,it can avoid the risks by decrease the highest temperature allowed when the lines run.With the development of short current forecasting,the proposed model will be improved as well.At the same time,lines can run efficiently and economically.