Abstract
Power transformer protective relay should block the tripping during magnetizing inrush and rapidly
operate the tripping during internal faults. Recently, the frequency environment of power system has been
made more complicated and the quantity of 2nd frequency component in inrush state has been decreased
because of the improvement of core steel. And then, traditional approaches will likely be maloperated in
the case of magnetizing inrush with low second harmonic component and internal faults with high second
harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection
sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy-based
relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and
percentage differential characteristic curve. The proposed relaying was tested with MATLAB simulation
software and showed a fast and accurate trip operation.
operate the tripping during internal faults. Recently, the frequency environment of power system has been
made more complicated and the quantity of 2nd frequency component in inrush state has been decreased
because of the improvement of core steel. And then, traditional approaches will likely be maloperated in
the case of magnetizing inrush with low second harmonic component and internal faults with high second
harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection
sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy-based
relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and
percentage differential characteristic curve. The proposed relaying was tested with MATLAB simulation
software and showed a fast and accurate trip operation.
Keywords
flux-differential current
Fuzzy logic
internal faults
magnetizing inrush
Power transformer
protective relay.