Abstract
To overcome the contradiction between speed and reliability in existing busbar protection schemes, a new busbar protection algorithm based on a polarity comparison of fundamental frequency currents is proposed. The algorithm extracts the fundamental frequency components of the fault reference current and the virtual current through a wavelet transform. The angle between the two currents is used to characterize the polarity relationship. The polarities of the virtual current and the reference current are the same when an internal fault occurs, and the angle will be small. The polarities of the two currents are opposite for an external fault, in which case the angle is larger. By analysing the variation characteristics of the angle between faults inside and outside busbar, a protection criterion is established, and the fault area is determined. In simulation results based on PSCAD/EMTDC, the algorithm can quickly and reliably identify the faults inside and outside the busbar area, and its performance is not affected by the initial fault angle, fault resistance, fault type or capacitor voltage transformer (CVT) transmission characteristics.
Highlights
Accurate identification of the fault area after a busbar fault will help quickly remove the fault and improve the stability of the power system [1]
The sensitivity of the busbar protection based on the comparison of the travelling wave polarity is very low, which will affect the judgement of the fault area
The simulation results show that when the fault occurs outside the area, the angle between the reference current and virtual current is not affected by the initial angle of the fault, criterion (15) is not satisfied, and the fault is judged to be an external fault
Summary
Accurate identification of the fault area after a busbar fault will help quickly remove the fault and improve the stability of the power system [1]. [11] proposed a busbar protection principle based on a wavelet transform and a travelling wave polarity comparison. To overcome the shortcomings of traditional travelling wave protection, a new principle of busbar protection based on a polarity comparison of the fundamental frequency components is proposed in this paper. When the initial angle of the voltage fault is small, the amplitude of the fault voltage is small At this time, the sensitivity of the busbar protection based on the comparison of the travelling wave polarity is very low, which will affect the judgement of the fault area. To solve the above problems, a new principle of busbar protection based on a comparison of the reference current and the virtual current polarity is proposed to improve the reliability and sensitivity of the protection.
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