HVDC Transmission Line Fault Ranging Method Based On GST-TT Transform

Due to the long transmission distance and the complex and changeable geographical environment,it is difficult and costly to detect the fault after the transmission line fails in the aspect of high voltage direct current transmission line fault ranging.Therefore,to improve the power supply stability of the high voltage direct current transmission system,the further development of high voltage direct current fault ranging technology is of great significance to the safe and stable operation of the power system.In order to improve the accuracy of the high voltage direct current transmission line fault traveling wave ranging method,this paper proposes to combine the generalized S transform and the TT transform to apply the fault ranging aiming at the problem of low accuracy in identifying and calibrating the fault traveling wave.The propagation characteristics of the fault traveling wave in the transmission line are analyzed based on to the simulation model of the high voltage direct current transmission system.Meanwhile,the calculation formulas of the fault distance corresponding to different fault location methods are determined respectively.In the single-terminal fault traveling wave ranging method,a GST-TT transform-based single-terminal fault traveling wave ranging method which does not depend on the specific traveling wave velocity is proposed.Firstly,the frequency range of fault characteristic frequency band is analyzed according to the changing trend of wave velocity of zero-sequence fault component and positive sequence fault component with frequency and the changing trend of frequency attenuation coefficient with frequency,and the sampling frequency is further determined.Secondly,the fault characteristic frequency band is extracted through generalized S transform.Thirdly,the characteristic frequency band of TT transform’s diagonal position is processed by gathering high frequency and suppressing low frequency,so as to identify and calibrate the corresponding wave head and its corresponding time.Finally,the fault distance is calculated according to the fault distance calculation formula.Similarly,the generalized S transform and TT transform processing methods for wave heads are extended to the two-terminal fault ranging method,and a two-terminal fault traveling wave ranging method based on GST-TT transform can be developed.In the simulation verification,the idea of controlling irrelevant variables is used,and the fault distance,transition resistance and noise intensity are respectively used as dependent variables to set different fault operating states,and the corresponding fault distance is calculated according to the relevant calculation formula.At the same time,compared with the fault ranging method based on the combination of wavelet packet transform and modulus maximum principle,the corresponding conclusions are drawn.In order to verify the fault traveling wave ranging method based on GST-TT transform,the±500k V bipolar EHVDC transmission system model was established in PSCAD.Through simulation verification,the following conclusions are drawn: First,the single-terminal fault traveling wave ranging method based on GST-TT transform has the advantages of high ranging accuracy,strong ability to withstand transition resistance and good anti-noise performance;Second,Compared with the single-terminal fault traveling wave ranging method based on GST-TT transform,the double-terminal fault traveling wave ranging method based on GST-TT transform not only has the advantage of high ranging accuracy,but also has the better ability to withstand transition resistance and anti-noise performance.Comprehensive simulation verification results show that the fault traveling wave ranging method based on GST-TT transform improves the accuracy of fault traveling wave’s wave head identification and calibration,thereby improving the accuracy of fault ranging.The paper has 45 pictures,11 tables,and 72 references.