The Research On Protection For UHVDC Transmission Line And Fault Location Of Electrode Line Based On Actual Fault Data

HVDC transmission line distance is long and it is located in the region of the environment is more complex, so the probability of failure of DC line is large. However, the actual practice shows that the protection rate of DC line protection is only 50%, Nearly half of the DC line fault is completed by the control system. There are two main lines in the research on the new protection method of DC line:The first main line is still the use of analytical method to construct the HVD internal and external fault identification criteria. However, the protection algorithm is different from the current protection, that is, the relative change of the electric quantity is used to construct the protection criterion. The second main line is based on the mathematical statistics method, under the consideration of various fault conditions, the extraction of the most able to characterize the amount of fault characteristics, and use it to build a protection criterion. The biggest feature of the algorithm is that it can continuously reuse the historical data to improve the performance of protection.The fault location of the grounding line is the use of the existing fault recording data.The main work of this paper is as follows:The current measured the filter branch is caused by the fault and does not contain the load current, which can better reflect the fault characteristics. Therefore, the reliability and sensitivity of the protection criterion is higher. Fractal box dimension and multiracial spectrum is used to describe the current waveforms obtained from the measurement of the branch of the filter under internal fault and external fault, and based on this protection criterion is formed. The protection criterion can tolerate high resistance fault.Under current DC protection sampling rate, PCA clustering analysis is used to describe and characterize the voltage waveforms of the time domain at different positions and the protection criterion without the need of setting value is constructed. The protection method can improve the situation of the refusal-operation of protection when the du/dt is approach and not achieve the protection set because of the discrete nature of the sampling or line fault with transition resistance. The protection method can reuse the historical fault data to improve the protection of the components and improve the reliability of protection.The instantaneous current curve of the forward and reverse faults is able to describe the direction of the fault. PCA clustering analysis method is used to quantitatively characterize the direction of failure and constitute the PCA direction element. The longitudinal differential protection is built based on the rectifier side and the inverter side arranged a PCA direction element. The time required for the longitudinal differential protection is relatively short, so the control system will not respond before the longitudinal differential protection, and can be reliable when the HIF happen. The time required for the longitudinal differential protection is relatively short, so the control system will not respond before the longitudinal differential protection.When DC pole line caused by fault, the fault voltage measured fault line measurement in a period of time is falling in the overall trend. When the line without fault andthe other pole line with fault, the fault voltage component is generally around the time axis changes. At the same time, combined with the PCA fault identification element, it is a new type of main protection of DC line, and with the current DC line traveling wave protection combined with the configuration in the DC line, which can improve the quality of the DC line protection.In the actual fault recorded wave device 6.4kHz sampling rate, The main frequency components of the voltage and current obtained by the measuring terminal are analyzed when electrode line with fault and The voltage and current of the 600Hz are used for fault location. Before the fault data is used to the obtain value of pole resistance.The location algorithm in the half line outside the fault location accuracy is higher, and the near end fault location precision is slightly lower.