This paper presents a pilot protection method for UHV transmission lines based on negative sequence impedance angle, which can reflect the total fault type. In this method, the memory function of microprocessor is used to extract window data of one cycle for delay processing. Meanwhile, the variable is introduced to make artificial asymmetric fault and produce negative sequence component, which makes the negative sequence admittance angle discriminator applicable to all types of short circuit faults. Based on PSCAD / EMTDC, a 1000 kV transmission line and its fault model are built. At the same time, a large number of line simulation are carried out. It is verified that the method can reflect different fault conditions and basically meet the requirements of UHV line relay protection.
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