Abstract
A new fast busbar protection algorithm based on the comparison of the similarity of back-wave waveforms is proposed in this paper. The S-transform is performed on the back-wave from each defected transmission line connected to the busbar, and the protection criterion is thus constructed by using the Euclidean distance to analyze the similarity of the back-waves, with the implementation of the S-transform between the transmission lines. When a fault occurs internally on the busbar, the Euclidean distance of the S-transformed back-wave between each associated transmission line is small, and there is a remarkable similarity between the waveform. When a fault occurs externally on the busbar, the Euclidean distance of the S-transformed backward traveling wave between the faulty line and the nonfaulty line is larger than that between the nonfaulty lines. The wave-forms of the faulty line and the nonfaulty line bear little similarity, while there is a striking similarity between the nonfaulty lines. Therefore, a protection criterion is established according to the ratio between the maximal similarity and the minimal similarity to discriminate the internal and external faults of the busbar zones. The simulation results show that the proposed busbar protection method can discriminate the internal and external faults of busbar zones in a sensitive and reliable way.
Highlights
In high-voltage power grids, busbar faults cause large-scale power outages and stable damage to the power system
The S-transform is performed on the back-wave from each defected transmission line connected to the busbar, and the protection criterion is constructed by using the Euclidean distance to analyze the similarity of the backwaves, with the implementation of the S-transform between the transmission lines
Based on the Euclidean distance algorithm, a busbar protection principle is proposed in this paper
Summary
In high-voltage power grids, busbar faults cause large-scale power outages and stable damage to the power system. To overcome the deficiency of traditional busbar protection against CT saturation and the contradiction between speed and reliability, and based on the theory of directional traveling waves and the correlation degree described in reference [17,18] combined with the application of an S-transform in a power system, this paper obtains the backward traveling wave after an S-transform of each related line of the busbar in a period of time after a fault. Compared with traditional traveling wave protection, it is more sensitive and reliable to use the current polarity or amplitude as the criterion, and an S-transform plays a filtering role in processing the traveling wave signal to a certain extent, as well as having a certain anti-noise ability. According to the analysis, when a fault occurs within the busbar zone, only forward traveling waves of each transmission line can be detected in the time period [t0, t0 + 2dmin/v]. The discrete S-transform of the signal h(t) is: S1⁄2kT;
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