Phase selection of high-impedance faults on EHV/UHV transmission lines based on sequence currents phase difference

LIAO Dong-jin， LU Yan
（School of Information Engineering， Quzhou College of Technology， Quzhou 324000，China）

Abstract： In order to realize the fault diagnosis quickly for EHV or UHV power transmission line，the technology of sequence current phase difference was applied to the phase selection of high-impedance fault on transmission line. After the analysis of the single-phase-to-ground fault and two-phase-to-ground fault in  three-phase network，the phase-to-phase fault was partitioned based on the phase difference of negative and zero sequence current components. The relationship between the fault type，fault phase and the protection region of sequence current phase difference，phase impedance，phase-to-phase impedance and 3-stage distance relay was established. A method was presented to judge the phase selection of high-impedance fault on EHV or UHV power transmission line based on sequence current phase difference. The accuracy and reliability of this fault phase selection scheme were evaluated for the 500 kV，400 km transmission line，and RTDS experimental simulations were tested. The experimental results show that the accurate and reliable recognition of this fault phase selection scheme can be realized，the unexpected factor can be dealt with，and error can be calculated with so enough time，the fault phase selection can be reliably realized，even if the system is on power grid oscillations.
Key words： transmission lines；sequence current phase difference；extra-high voltage（EHV）； ultra-high votage（UHV）；fault phase selection；fault diagnosis