Transient Simulationof Heat Balance And Risk Assessment On Overhead Transmission Line

The operation of power grid in different environment has been requesting highersafety with the development of economy and increasing electricity demand, which hasbecome a research hotspot.. Based on the theory of thermodynamics and fluidmechanics, this paper simulated transient thermal balance of overhead transmissionline, and carried on relating risk assessment which focused on one of the running stateof the transmission lines in Chongqing.Main research content is as follows:(1) Overhead line transient thermal balance model is established, depending onthermodynamics and fluid mechanics theory. Based on environmental factors, we builta geometric model as well as set the corresponding boundary conditions and initialconditions, which was verified by grid independence.(2) The change characteristic of the overhead transmission line transient thermalbalance was simulated in this paper.70℃was set as security temperature.We obtainedthat the safety time reduced with the conductor temperature rising gradually. The resultsshowed that the main factors influencing the safety time was wind speed, wind angle,carrying capacity, environmental temperature and sunlight intensity. The wind speedaccelerated the convective heat transfer between the conductor and the externalenvironment, and the safety time increased rapidly with the increase of wind speed. Theeffective wind speed had cooling effect on the surface of a conductor When the windangle was divided: the bigger wind angle, the less security time. The change of carryingcapacity could cause the joule heat increasing, thus the safety time would reduce quickly.The steady-state temperature changed about1℃when environment temperaturechanged1℃,showing that the transient security time increased with the temperaturedecreasing. However, the security time impacted by sunshine intensity could be ignored.(3) Using the analytic hierarchy process (AHP), a risk assessment was carried outbased on the results of the numerical simulation and real-time monitoring data. Theresults provided theoretical basis for safe operation.