Analysis And Research On Dynamic Ampacity Of Cable

With the scientific and technological progress,people's living standards continue to improve;the whole society's demand for electricity is growing day by day.As the most important carrier in the transmission and application of energy,Cable's maximum load current is called the cable ampacity,the cable ampacity research has always been caught attention.So far,most of the research on cable ampacity has been carried out around the steady-state ampacity,and the research on dynamic current ampacity has started late and lacks systematic results.Comprehensive analysis of the research results of dynamic cable ampacity can be drawn: Cable conductor temperature is the most important in the study of dynamic ampacity.If the real-time temperature data of the cable conductor can be obtained in the running state,the running status of cable can be monitored and controlled in real time according to the data,and guide the safety scheduling problem of the instantaneous increase of cable load according to the conductor temperature rise characteristic.At the same time,it's conducive to cable load monitoring and optimization of cable operation.In this thesis,dynamic thermal load model of cable is researched based on the traditional calculation method of cable ampacity.The major work is as follows:First,the dynamic calculation of the cable thermal field is carried out.Construction and calculation method of cable thermal field model is demonstrated in detail.The cable thermal circuit model is compared with the circuit model by introducing the classical theory of heat transfer.Based on the calculation method of traditional cable ampacity,the calculation of cable thermal field is discussed,and then edits the Matlab program to achieve the real-time calculation of cable each layer's temperature under fixed ampacity and dynamic changing ampacity.That is verified the calculation of the classical ampacity is cautious,but also obtain what the actual ampacity can be extended.Then,the effect of external heat source on ampacity of cable was explored.According to the cable ampacity formula which is introduced by IEC60287-3-3(2005)standards in the cross-heat source conditions,combined with the heat source around cable on the impact of ambient temperature,with the Kennelly principle,using iterative method,calculates the ampacity reduction factor caused by a single cross-heat source and a number of cross-heat source respectively.Finally,the analysis system of cable dynamic ampacity and thermal field is designed.Combined with the conditions of project construction about Yan Chang A#13 and Yan Chang B#13 designed by Liaoning Survey and Design Institute,in the case of known cable data parameters and basic laying mode situations,thermal field analysis system of cable dynamic ampacity is designed through applying the GUI in Matlab.Dynamic analysis of cable thermal field data under complicated conditions is achieved,and the actual cable load in the corresponding case is predicted.This can lay a foundation for engineering application of cable dynamic ampacity prediction and thermal field analysis.