Aging Characteristics And Monitoring Technology Of Roof Arrester Of EMU Under Frequent Overvoltage

With the rapid development of high-speed trains and the wide application of power eletriconic devices,higher harmonics and frequent overvoltage in the railway system have put forward higher requirements for the stable operation of the roof arresters of EMUs.As an important overvoltage protection device,the arrester plays an essential role in the railway system by virtue of its excellent nonlinear electrical characteristics,but it is subjected to long-term power frequency voltage and harmonic overvoltage in the service process,which makes the zinc oxide resistor in the arrester.The resisitor is prone to aging,which directly affects the safe and reliable operation of the EMU.The current monitoring technology for arresters is mostly used in power system,and the internal mechanism and online monitoring system for the aging of arresters of EMUs are not yet perfect.In order to explore the aging process of the the arrester of the EMU under frequent overvoltage,a high frequency and high voltage tset platform and valt-ampere characteristic test platform were built to analyze the change characteristics of the voltampere curve of the Zn O resisitor after long-term high frequency and high voltage action,and the Zn O resisitor aging mechanism was revealed.Taking the 27.5k V EMU roof arrester as the object,a proportional medel was established to study the temperature rise distribution of the arrester under high frequency voltage,and the arrester overheat monitoring and early waring system was initially proposed.Firstly,according to the characteristics of frequency over-phase overvoltage of the EMU,the high-frequency and high-voltage aging test of the Zn O resistor was carried out,and the change of the internal electrical parameters of the Zn O resistor before and after the aging test was compared through the resistor volt-ampere characteristics test platform.The surface morphology and internal microstructure of the aged Zn O resistor were observed and compared with the test results of the unaged resistor in the same test scheme.A two-dimensional axisymmetric of Zn O arrester was established,the heat transfer process of the arrester was studied,and the variation of the temperature rise inside and outside the arrester with the voltage amplitude under higher harmonics was dicussed.According to the thermal balance law of the arrester,the voltage amplitede at which the arrester reach the limit temperature rise under high-order harmonics was explored.Finally,combined with the current situation of the overvoltage damage suffered by the arrester when the EMU is running on the power supply arm,a method of monitoring and early warning of the arrester was initially proposed.The voltage and leakage current at both ends of the arrester were monitored synchronously,the alarm threshold for overheating of the arrester was calculated.When the limit value is approached or exceeded,an alert will sound.The research in this dissertation provides theoretical basis and data support for the selection,design,optimization and operation and maintenance of arresters for high-speed EMUs.