Study On Adaptive Reclosure For Transmission Line Based On Support Vector Machine

Power system transmission lines are the highest failure rate link and the most common faults are short circuit fault. Domestic and foreign technology widely use auto-reclosing to restore power to the continuity quickly and improve system stability. However, the current automatic reclosing is reclosing automatically after a fixed time limit which will lead to the danger of blind reclosing onto a permanent fault. This technology may threaten the safe operation of power system important electrical equipments. It is important to study on the ability of discriminate transient faults and permanent faults before reclose in adaptive reclosing EHV/UHV power grid.This paper discusses, with/without shunt reactors transmission lines for the study, from single-phase and three-phase transmission line two aspects of a permanent fault identification method and carries out following specific research work:(1) Although the transient information of the fault phase are of abundant in primary arc period and secondary arc period, however it is difficult to obtain true nature of the arc. The characteristics of the recovery voltage and current in the shunt reactor in open phase are analyzed. Theoretical analysis and simulation results show that there is a clear distinction in characteristic quantities of faulted phase terminal voltage between transient fault and permanent fault. And the magnitude current in the shunt reactor is more reliable whether in transient fault and permanent fault. Therefore, using the stable and reliable data in the voltage-recovery period is promised to assure the reliability of fault nature identification, which provides theoretical basis for the voltage and current-based techniques.(2) When transient single-phase fault occurs in transmission line with on shunt reactor, the waveform of terminal voltage in the open phase is significantly different from permanent fault ones. Due to the differences, using wavelet transform to extract fault characteristic quantities of terminal voltage in the open phase, and using support vector machine to identify the characteristic quantities. On the basis of wavelet transform and support vector machine, A single-phase permanent fault identification criterion is proposed based on the wavelet transform and support vector machine. Simulation results show that this identification method have highly reliability, and is helpfor to apply to any distance transmission line without shunt reactors.(3) When single-phase fault occurs in transmission line with shunt reactor, the ratio of current amplitude in the shunt reactor and the neutral reactor exist obvious difference between transient fault and permanent fault. This difference can as a characteristic quantity to distinguish two different type of fault. An intelligent single-phase adaptive reclosing based the current characteristics in the open phase shunt reactor is proposed, with the help of support vector machine which having excellent learning ability. ATP simulation results show that the identification method is simple, can accurately distinguish transient and permanent faults, and is promised to meet the transmission line with one or two terminal shunt reactors.(4) When a phase-phase faults occurs in transmission line with shunt reactor, the line lost contact with power after three-phase tripping. However, due to distributed capacitances, shunt reactors and other energy storage devices, there is still enough time and valid information to distinguish nature of the fault. Electrical quantities of fault phase between recovery-voltage period are deeply analyzed in the types of fault:two phases short-circuit to ground (non ground), three-phase short circuit. In each short circuit case characteristic quantity is captured to distinguish permanent faults from transient faults. Finally, the permanent fault identifications are proposed based on support vector machine for each faults cases. The simulation results show that, the scheme can effectively distinguish transient faults and permanent fault. In addition, this method only use single-ended electrical quantity, easy to realize, wide application, can effectively improve the success rate of reclosing.At last, the practical single-phase adaptive reclosure scheme applys for transmission line are proposed. The practical single-phase and three-phase adaptive reclosure scheme apply for transmission line with shunt reactor also are gived, after the characteristics of above identification methods are discussed. This provides a feasible scheme for practical application of adaptive reclosure.