Research On Wide-area Relaying Protection And Adaptive Reclosing Technique For Parallel Lines On The Same Tower

Wide-area relaying protection based on wide-area multipoint information becomes one of the hottest researches in power system with the frequent occurrence of large blackout accidents and development of smart grid. At present, researches on the wide-area relaying protection principles and preliminary exploration has achieved some good results, this paper aims to sort out these technical results. First analyzes the main protection principles utilized in wide-area relaying protection system, with regard to the research status and exiting problems, this paper proposes some suggestions. From the application aspect, both the system structures and the division methods for information domain are expounded. How to apply related information technologies such as IEC61850 standard, multi-agent technology and grid computing technology to the wide-area relaying protection system has also been investigated in this paper.Double-circuit transmission lines on the same tower have been more and more widely used in China's EHV transmission system, because of its economic efficiency. In order to ensure continuous power supply and stable operation of power system, the study on the adaptive reclosing technology applied into the double-circuit transmission lines is of great practical significance. The adaptive reclosing technology in the double-circuit transmission line usually employs the voltage amplitude criterion which is deduced in this paper to distinguish fault nature. From the process of the deducing, we can conclude that the recovery voltage at open-phase has a different nature in different property fault cases, the impact of various factors on the criterion and the application scope of the criterion.Considering that there are so many shunt reactors with neutral small reactors in HV transmission lines to compensate the capacitive current, this paper analyzes the transient characteristics of recovery voltage at open-phase in detail by Laplace frequency domain analysis in transmission line with shunt reactors. Because of the initial energy in the exiting shunt reactors, the terminal voltage at open-phase contains more components than only fundamental frequency component. For transient fault, the terminal voltage at open-phase not only contains fundamental frequency component, but also contains the free oscillation component which is produced by the initial energy in shunt reactors. But for permanent fault, the terminal voltage at open-phase contains only fundamental frequency component. Based on this feature, voltage integral criterion can be applied to the double-circuit transmission line. The principle of this method is to make an integral of the recovery voltage during a fundamental frequency cycle. This criterion is simple for implementation, and it distinguishes the fault nature with high sensitivity, reliability and accuracy.Besides single line fault, there will be cross-line fault in the double-circuit transmission line. For transient fault, the terminal voltage at open-phase contains one more free oscillation components. Improved voltage integral criterion is proposed in this paper, theoretical analysis and simulation results demonstrate the reliability and accuracy of the voltage integral criterion when applied into the double-circuit line multiphase adaptive reclosing.When power system frequency fluctuates, the application of voltage integral criterion in the single transmission line and double-circuit transmission line is also compared in this paper. Theoretical analysis and simulation results demonstrate that, when applied into the double-circuit transmission line, the voltage integral criterion possesses higher accuracy and discrimination degree, even in the extreme cases, the criterion can also distinguish the fault nature with high sensitivity and accuracy.