Study On The Method Of Fault Phase Selection For UHV Transmission Line

The UHV transmission line has became the backbone of the power system and acts an important role to the security and stabilization of power system operation. The requirements of the protective relays and security equipments are stricter than ever. Fault-phase selector is an important element of the UHV transmission protection and correspondingly its performance need to be promoted. This paper summaries roundly about the development and current situation of fault-phase selection, the main contents are as following:1 Analyzed the basic theory and the defect of the superimposed phase selector, put forward a new method which has better performance, in the new scheme, the fault component of phase to phase voltage difference is polarized with the voltage change ratio of the of the third phase.2 Analyzed the angle relationship between superimposed positive-sequence and negative-sequence for double-phase-earth fault, an efficient method for determining the fault phases is proposed, using the vector relationship of the three sequencecomponent to distinguish the different faults at the same zone.3 The mismatch of the fault phase selection and the criterion for the asymmetry fault during the power swing are investigated, draw some useful conclusions and put forward the innovative methods which use the change ratio of the cosine voltage and the resistance, the new methods can promote the performance of fault phase selector during the power swing.4 Puts forward a new fault phase selector of zero-sequence differential protection, using the relation of zero-sequence and negative-sequence differential current and the magnitude of three phase line differential current. The results verify that the fault phase selector can select the fault phase correctly and fast after simulate the 1000 kV transmission lines.