The Fault Protection Technique Of Transmission Lines Double-circuits On Same Tower For High Voltage Grid

The double-circuits electric transmission line fault protection technique of the same tower side by side of the high voltage grid system are mainly studied in this paper, the automated reclose is adopted for the instantaneous fault of electric transmission line in order to make the fault shut off and to recirculate the transmission line, which, therefore, improve the reliability of power supply greatly, and enhance the stability of the parallel operation as well.The causes, types and results of the short circuit fault are mainly stated in this paper, the transient process of the short circuit is also analysed in detail, and the short circuit model is built up, then the method of the rate of current changing is applied to the criterion whether the short fault takes place, which further meets the request of the short circuit protection. Meanwhile, the calculation method of the short circuit current is analyzed, and the simulation data of the experiment is gained by MATLAB simulating the fault types of the short circuit. The calculation method which is adopted in this paper can pick up the fundamental component before and after the short circuit quite accurately, which provide proof for the setting of the protection and the adjusting of the parameter.The method of identifying the severe permanent fault and the instantaneous fault is studied in this paper, and the method of judging the blowing out of arc at the fault point is done as well, which can effectively identify the grounded instantaneous and severe permanent fault. In this paper, the technical principle and setting scheme which is suited to the double-circuits electric transmission line of same tower side by side of the relaying protection and reclose is brought forwarded. Of this paper, the scheme that dependent on the fault phase trip and nonsevere fault reclosing of the phase combination can sufficiently keep two ends of the system in connection during the fault period, while increasing the opportunity of the reclose and avoiding reclose at the severe permanent fault. This scheme not only solving the correct choosing phase and fast trip problem of any fault for the double-circuits electric transmission line of same tower side by side, also resolving the potential reclosing at multi-phase permanent fault for traditional reclose in the double-circuits electric transmission line of same tower, which may cause severe impact and destabilization on the system, is a feasible one geared to the situation of our country at present.