Study And Practice On Online Rating System For Transmission Components

Comparing to the fast development of national economy, the construction of transmission corridor has lagged behind, which makes how to effectively dig potential transmission capability based on current power system a problem requiring immediate solution. For a long time, the static thermal rating is used as the transmission line’s maximum transmission capability in project application, which, unfortunately, neglects the variation of actual meteorological environment and running condition and consequently cannot reflect the real loading capability; thus, it causes underusing of the power system’s real capacity, or, even worse, threatening to the power system running security. Via real-time measurement of the current, temperature and the environment factors, Dynamic Thermal Rating (DTR) technology can realize online tracking and predicting the temperature of the transmission line to evaluate its thermal loading capability economic, reliably and effectively; however, the requirement of installation of expensive assistant equipments on the transmission lines hinders greatly the popularization of this technology. Meanwhile, the running conditions of the transmission lines also impact its capability besides the physical property in itself. Based on online tracking and predicting the transmission line’s temperature to determine its thermal transmission capability, while combining the running conditions’analysis, a more accurate estimation of the transmission line’s real-time loading capability can be obtained. These are the researching background and significance of this paper.On account of the background, this paper uses the so called soft DTR (SDTR) idea, with real-time data from SCADA, forms a transmission line SDTR model, and finally realizes temperature estimation and prediction without other equipments requirement. Further, with the acknowledged research works and the temperature estimation and prediction technique, this paper practices the transmission line’s online load-ability rating technology, thus testifies its effectiveness and economy, and furthermore completes the transmission line’s online load-ability rating system software, which is now working in actual power system. The main research includes following aspects.First, a SDTR model is proposed based on the SDTR idea and via analysis of the non-steady-state heat balance equation parameters in IEEE standard, and based on the extensive state estimation, the transmission component’s resistance can be obtained as well as its temperature track by using the resistance’s thermal characteristics; finally track the time-varying parameters of the SDTR model with consequential estimated temperature series, and that is to realize DTR. This method need not add equipments to transmission lines, and its simplicity, quickness and accuracy of the result can totally meet engineering requirements, thus it has good economical efficiency and practical applicability.Second, on basis of SDTR technology, analyzes the transmission component’s online thermal rating status; furthermore, with the predecessors’researching work as references, analyzes the transmission component’s comprehensive rating status taking its running conditions into consideration, hence completes the online comprehensive load-ability rating system and testifies its effectiveness. The practice result shows that transmission component’s online load-ability rating technology based on SDTR model can give comparatively accurate assessment on transmission line’s actual loading ability and effectively dig its underlying capability.Finally, based on the above, this paper completes the development of transmission component’s online load-ability rating system software and applies it in Yantai power grid. This system agrees with actual project, is easy to operate, calculates fast, and gives comparatively credible analyzing results of Yantai power grid, which supplies helpful information to grid dispatching and controlling as references.In a word, the transmission component’s online load-ability rating technology based on SDTR technique is helpful to accurately assess the real capacity of transmission lines, and is in favor of regional grid’s running economy, security and reliability. Therefore, with its development, this technology would have wide application prospect.