Research On An Online Decision Support System Of Overhead Transmission Line Dynamic Rating

With continuous rapid increase of electricity consumption and increasingly difficulty in building new transmission lines,the transmission line capacity of power grid cannot support the rapid increase of electricity power demand gradually,which increases the risks of power grid security operation.According to the overhead transmission line design technical regulation in China,the thermal ratings or maximum allowable currents are calculated under the conditions of worst operating environment,critical temperatures,etc.,which lead to the underutilization of existing power equipments.To solve above problems,the dynamic thermal circuit rating(DTCR)method is researched by this paper.The research of complex thermal equilibrium process between overhead transmission line and ambient air is the key of the dynamic thermal circuit rating,which involves current,conductor temperature,sag,conductor tension,variation of wind,ambient temperature etc.Firstly,based on the research results of existing maximum allowable current calculation models,a new simple calculation model with higher precision is constructed by this paper,which does not require monitoring the environmental parameters by the scene simulation of running line.Secondly,the primary limitation on line capacity that transmission line sags is researched,and the traveling wave transmission time differences based online sag monitoring is proposed to improve the precision of existing sag monitoring measures.Thirdly,by the deeply analysis of the relationship among sags conductor temperature and traveling wave transmission time differences,the conductor temperature calculation model based on the traveling wave transmission time differences is also constructed,which correct the measured values of the transmission time differences and conductor temperature in real time.Then the experiments are executed to verify the accuracy and precision of the above proposed calculation model Finally,an online decision support system of overhead transmission line dynamic rating is designed to realize the precision determination of thermal rating,ampacity safety pre-warning and correction of scheduling schemes,and related equipments of traveling wave sensor,precocious synchronization clock,and power supply are also designed.It can realize the real-time,accurate,safe and orderly dynamic rating of transmission lines with the proposed series model and dynamic rating online decision support system,which can solve the engineering application problems of DTCR and improve the related theoretical research level.