Research On Protection Scheme Of Cable Continuous Line With 10kV Neutral Point Ungrounded In High-speed Railway

As the power supply line of the railway signal,communication and other comprehensive railway power system,the power continuous line is an important part of the railway power system.With the rapid development of electrified railways in China,the national railway operating mileage has exceeded 150,000 kilometers by the end of 2021,including 41,000 kilometers of high-speed rail.Such a huge transportation system puts forward higher requirements on the reliability of the power continuous line.However,traditional power continuous line protection suffers from insufficient reliability and selectivity.Considering that the box-type substation along the line is equipped with a load switch,if the fault location can be located,it can isolate the fault without affecting the load power supply and improve the protection selectivity.For this reason,this paper proposes a fault section identification algorithm for the 10 k V neutral point ungrounded cable continuous line of high-speed railway,and designs a protection scheme including fault isolation based on this algorithm.The solution is implemented based on communication,which can quickly find faults,remove faulty sections,and restore power to non-faulty sections.This paper firstly analyzes the structural characteristics of the high-speed railway 10 k V cable continuous line.Based on the zero-sequence network of the system,the changing trends of the stable and transient components of the zero-sequence current at both ends of each power supply section under stable single-phase-to-ground faults are clarified.In addition,the difference and variation characteristics of the phase currents on both sides of the fault point under the phase-to-phase fault are analyzed.Aiming at the stable single-phase grounding fault and phase-to-phase fault of the cable continuous line,it is found that the variation trend of the zero-sequence current or phase current at both ends of the fault section is quite different,rather than the same change trend at both ends of the fault section.The above characteristics are verified by establishing a system model in MATLAB/Simulink software for simulation.Secondly,the development process of arc overvoltage in the system under the occurrence of intermittent arc grounding faults is revealed.And the change trend of the zerosequence current at both ends of each power supply section in the arcing stage and the arcextinguishing stage of the arc ground fault is analyzed.Based on the relevant characteristics of AC arc,an arc model is established,and the intermittent arc grounding fault simulation of the cable continuous line is carried out to verify the variation trend of the zero-sequence current at both ends of the power supply section under the fault.Furthermore,according to the difference of the current change trend between the faulted section and the non-faulted section in the case of stable single-phase ground fault,intermittent arc ground fault and interphase short-circuit fault,a fault section identification algorithm based on the current change trend is designed.Its features of wide application and high reliability are verified by simulation.Finally,based on the fault identification algorithm,a set of protection scheme including fault isolation is proposed for the 10 k V neutral point ungrounded cable continuous line of high-speed railway.The solution can quickly restore the power supply of the load under the condition of removing the faulty section,and improve the reliability of the power supply of the system.