Research On High Voltage Cable Test And Insulation Status Evaluation Of Railway 27.5kV System

With the rapid development of China’s high-speed railway infrastructure at the present stage,the railway power supply equipment has also ushered in great development,and the equipment is more concentrated and concise.The overhead outlets of the traditional substation are gradually replaced by power cables and GIS switchgear.The high-speed EMUs design also requires a large number of high voltage cables for railway-specific voltage ratings.The stability of high-voltage cable is an important part of operational safety and one of the key links to ensure the overall safe and reliable operation of the railway traction power supply system.Since most of the railway high-voltage cables are installed outdoors,the open-air environment is affected by rain,fog and pollution.In addition,China’s climatic conditions,traction power supply and power quality are poor compared with those of foreign countries.The temperature difference is big and the pollution is serious.There are different types of motor trains or locomotives running in the traction network,and the harmonic content and overvoltage level in the network are relatively high.Therefore,higher requirements are put forward for the insulation tolerance of high voltage cables.Once the high-voltage cable has a ground short-circuit accident,the strong short-circuit current of the traction power supply system will flow through the short-circuit point,causing the conductor flowing through the short-circuit current to generate heat,and the accompanying high-voltage arc may cause the high-voltage equipment and accessories to burn.Under the double-clamping effect of the "bathtub curve" of cable life and the generally low installation quality of railway construction attachments,the annual failure times and average failure rates of railway line high-voltage cables are on the rise.This paper first introduces the principle,advantages and disadvantages of existing conventional cable withstand voltage test methods and analyzes the applicable standards on railway cables.On this basis,the latest cable insulation condition assessment technology,ultra-low frequency dielectric loss test,damped oscillation wave test technology and cable on-line detection technology are introduced in detail.They are new cable condition detection methods in China,and are the research hotspots at home and abroad.This paper studies the test principle,test method and test result analysis of these advanced detection technologies by consulting domestic and foreign materials.Finally,combined with the field test application of railway EMU cables,the field test experience and test data of railway cables are obtained.Combined with routine test,diagnostic test and other multi-dimensional test methods,a set of suggestions on cable and terminal insulation detection methods suitable for railway application environment are put forward,in order to reduce the accident rate of power outage and maintain the safety and stability of railway high-voltage cable operation.