Due to the distributed capacitance, the conventional current differential protection has unsatisfying performance. Considering matrix pencil algorithm can accurately analyze the composition of fault transient currents...
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ISBN:
(纸本)9781622761050
Due to the distributed capacitance, the conventional current differential protection has unsatisfying performance. Considering matrix pencil algorithm can accurately analyze the composition of fault transient currents, a novel pilot protection principle using only current data is proposed in this paper to solve the above problem. This principle adopts model recognition concept. Firstly, the theoretical expression for external fault is derived which describes the ratio between the sum and difference of two terminal fault component currents, and the expression is defined as the standard model. Then the model error function is established while the function measures the extent to which actual fault data accord with the standard model. When an external fault occurs, fault data correspond with the standard model and the model error equals zero. When an internal fault occurs, fault data do not correspond with the standard model and the model error is greater than zero. Therefore, external fault and internal fault are distinguished. This new principle is immune to the distributed capacitance and has high reliability without using voltage data. Moreover, the principle possesses fast operation speed and high sensitivity. Electromagnetic transient program (EMTP) simulation results verify the effectiveness of the proposed principle.
This paper proposes a novel transmission line protection scheme based on frequency-domain model identification method with distributed parameter. Integrated impedance is defined by voltages and currents of two end ter...
详细信息
ISBN:
(纸本)9781622761050
This paper proposes a novel transmission line protection scheme based on frequency-domain model identification method with distributed parameter. Integrated impedance is defined by voltages and currents of two end terminals of transmission line. By analyzing the frequency-domain expressions of integrated impedance in internal and external fault states, the amplitude-frequency characteristics of the integrated impedance are discussed. The integrated impedance in internal fault state shows system impedance characteristic and the integrated impedance in external fault state shows the line distributed capacitive characteristic. The frequency-domain model errors are defined as unbalanced currents respectively in order to identify the internal and external faults. matrix pencil algorithm is used to calculate the phasors in different frequencies in the proposed scheme. Protection criterions are designed and some tests are performed. The simulation results show that the proposed schemes can detect internal fault quickly and reliably. Furthermore, the influences from capacitive currents and transition resistances can be avoided in the proposed protection scheme.
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