| In consideration of the growth of national economy, the increasingdemand for electricity, the natural conditions as well as the distribution ofenergy in China, it has become an inevitable trend of long-distance andlarge-capacity power transmission. In order to reduce the power loss intransmission lines and save the land resource, HVDC transmission system isneeded.The protection of HVDC transmission line is very important for thesystem safe and stable operation. Therefore, it is essential to do furtherresearch and improvement. The summary of HVDC system power simulation,transmission line protection scheme and fault location is presented in thispaper.(1) Uni-polar12pulse HVDC line with ground return model is establishedbased on CIGRE DC transmission standard and PSCAD/EMTDC software.Some typical fault conditions have been simulated and analyzed. According tothat, the operation control manner and relay protection system are researched.(2) A new pilot protection based on polarity comparison is proposed through amplitude and direction difference comparison of transient current at bothends. Utilizing the dissimilarity of transient current waveforms at two ends,displacement deviation and product term of current changes are introduced.Thereby, the relevant criterion is proposed to distinguish the internal andexternal faults effectively. Simulation results show that the proposed schemehas high reliability.(3) New fault location method in HVDC transmission line is proposed. Themethod uses the voltage and current at both terminals of the transmissionlines to calculate the fault distance by means of solving balanced matrixequation. Simulation result shows that the method has good precision.Finally, summarized the whole-length main research content and themethod of research, through the results verify the correctness of the results ofthe study, the further study has certain reference value. |
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