Application Analysis And Risk Assessment Methods Of Dynamic Line Rating System For Overhead Transmission Line

As an important part of smart transmission line, Dynamic Line Rating(DLR) can improve the utilization of transmission equipment and help the operator to know the current operation status of transmission line. DLR technology was the most economical and most environmentally friendly technology to improve transmission capacity and solve the transmission bottleneck.This paper systematically explain the principles of the DLR system, which using tension sensors to realize the dynamic capacity-increase.Transmission line sag was an important parameter reflecting the line safe operation. Based on the practical application at home and abroad, this paper focused on using conductor temperature, tension and tilt angle sensors to monitor the sag and researched the accuracy on both theory and application. The result showed that all three method can meet the requirement of engineering and the error of all three methods was under 3% in which tension method have the small error under 1%. In order to ensure the reliability and safety of the transmission line, a method based on Markov chain Monte Carlo was proposed in this paper to assess the operation risk of transmission line which using DLR technology. The main principle of this method can be stated as follow. Firstly, random sequence of micro-climate monitoring parameters posterior distribution was used to create the wind direction, wind speed and ambient temperature probability distribution model. Secondly, Monte Carlo simulation was used to predict the distribution of conductor temperature with the climate models and line load current model. At last, the operation risk of transmission line was calculated by the conductor temperate distribution. Typical summer and winter monitor data was used to analyze the reliability of dynamic rating and the result indicated that the operation risk was within the safe range and meet the requirements of grid operation.Finally, because the transformers, circuit breaks, isolating switches and other power equipment have an important impact on the entire power grid transmission capacity, it's enssential to explore the heat cacacity of these equipments.This paper theoretically analyze the temperature standard, the causeses of the winding hot spot and the method to obtain the hot spot. And the steady-state and transient hot spot formulas of different cooling mode were given. Besides, the calculation methods for continuous current carring capacity, short-term overload capacity and emergency overload capacity of circuit breakers and isolating switches were given. Then using rich data confirm that increasing the entire power grid transmission capacity was feasible. And these work was a useful supplemet for DLR technology.