جستجوی مقالات مرتبط با کلیدواژه « Traveling waves » در نشریات گروه « برق »

In this paper, a novel high-speed protection scheme, for transmission lines based on initial current traveling waves and employing mathematical morphology (MM) is presented. This scheme, by comparing polarity and arrival time of initial current traveling wave from two terminals of the protected line, can discriminate the fault direction and internal faults from external faults rapidly. A new MM filter to extract transient components from fault-induced transient signals is designed. This MM filter can fast and accurately detect the arrival time and polarity of traveling waves in all conditions. Extensive simulation studies using EMTP and MATLAB are performed to evaluate the validity and reliability of the proposed scheme. The simulation results show that the proposed protection scheme can fast and reliably discriminate the fault direction and the internal faults from external faults in the most of conditions, especially in high impedance fault and low inception angle fault situation The protection performance is immune to fault resistances, fault inception angles, fault types and fault location.

This paper proposes a new traveling wave-based fault location method for power transmission grids. The proposed method involves an online and an offline stage. In the offline stage, the transmission network is represented by a weighted graph. The shortest paths between any two sensors are determined. The branches of the graph that are not on at least one of the shortest path, are divided into virtual lines associated with the location of the sensors. In the online stage, according to first arrival time at different sensors, the points belonging to the shortest paths obtained during the offline stage with the possibility of having a fault are identified Then using an evaluation index, the exact point of fault and the fault inception time are determined. The proposed method is independent of the fault type and can be utilized in transmission network with any size. Simulation studies carried out using EMTP software and MATLAB, verify high accuracy of the proposed method.

A traveling wave based algorithm for fault classification and faulted phases selection is presented in this paper. The proposed algorithm is composed of two major stages. In the first stage, after extraction of modal components from three phase signals and by means of Teager energy operator (TEO), traveling waves are extracted from modal signals. Then ratios of initial traveling wave in different modal components are used for the fault classification and faulted phases selection purpose. TEO is a very simple method which can extract traveling waves with very high speed and resolution. In the second stage, fault classification and faulted phases selection is performed based on the information extracted from the previous stage. Intelligent methods are the best choice to be used in the second stage and for the first time are utilized in this paper. Fuzzy system, which is used in this paper as a classifier, is able to classify the faulted signal with a high accuracy. Simulation results show that the proposed algorithm has an efficient and accurate performance in terms of close-in faults, high impedance faults and faults with very low inception angle.