Research On Metal Shielding Of High Voltage Cable For EMU

the cable shielding structure of high-voltage dynamic cables of 26/45 k V used in high-speed railway carriages contains concentric conductor and braided shielding structure.In this paper,the mechanical properties of these two metal shielding structures are analyzed by finite element method and verified by experiments,and the terminal design of dynamic cable is also described.The research contents mainly include the following aspects:1.It is necessary to make sure the structure of metal shielding which has the effect of enhancing the mechanical properties of the cable and electromagnetic shielding.The common metal shielding forms for cables are copper/aluminum tubes,parallel-wound copper wires,and braided copper wires.In order to ensure that the dynamic high-voltage cable of the trains can withstand the complex and variable dynamic load during operation,the metal shielding form of the EMU cable is determined to be the concentric conductor and the braided copper wire.These two structures have extremely high requirements on the terminal connection technology.2.Finite element method was utilized to analysis the metal sheath properties.The shielding layer is composed of several thin copper wires,and there are a lot of contact behaviors during the process of drawing and bending.The distribution of shielding copper wire with space shuttle and helical geometry is proposed,and the mathematical model suitable for various shielding structures is developed.Based on LS-DYNA explicit algorithm,the stress/strain distribution of the metal shielding under the above external loads is simulated accurately,which shows that the braided shielding has better fatigue resistance than the concentric conductor shielding.3.The fatigue test of metal shielding is made.A dynamic test platform is built to measure the tension,bending and torsion properties of cables based on the actual running environment of EMU.The cable test is qualified without damage.Based on above tests,the physical property tests of cables is performed continuously,such as temperature rise test,temperature change test,high temperature test and low temperature test.The surface of the cable is intact and there is no cracking and damage,which provides further guarantee for the long-term reliable operation of the cable.4.Theory research was carried on to explore the relationship between transfer impedance and different working frequency.Electric field distribution was simulated around the termination.Based on the most strictly standard on high-speed railway carriages equipment,dynamic cable and termination were installed in the laboratory.Partial discharge and voltage tests proved the efficiency of the whole cable system.