Research On Heating Mechanism And Detection Method Of GIS Equipment

With the increase of input and use time of GIS equipment,the heating fault becomes more and more prominent.However,the internal heating of GIS equipment is not easy to detect because it is sealed in the metal shell filled with SF₆ gas,and the existing heating detection methods can not effectively monitor the heating condition of the equipment.Based on this phenomenon,this paper focuses on the characteristics of heating fault,heating mechanism and heating detection methods of GIS equipment.According to the simulation calculation,the heating temperature rise rules among components are obtained.In different cases,the corresponding heating detection methods and application requirements of GIS equipment are proposed.The specific research contents are as follows:?1?Introduce the GIS substation and its main equipment,and focus on the analysis of the characteristics of the main heating equipment-busbar and disconnector.?2?Based on the theory of heat transfer,the heating mechanism of GIS equipment is studied.The heat source and heat transfer process of busbar and disconnector are mainly studied and analyzed.?3?According to the actual structure of GIS bus and disconnector,a simplified physical model is established to simulate the temperature rise under power frequency and short circuit respectively.The generation of heat source is simulated by eddy current field calculation,and the multi-physical field coupling calculation of eddy current field-temperature field-flow field is carried out to analyze the temperature rise results.?4?The requirement analysis of engineering application for heating detection method of GIS equipment is carried out.According to the simulation results of temperature rise,the common heating detection methods of existing GIS equipment are introduced,including detection principle,detection characteristics analysis,application scope of detection methods,selection and installation of objects and sensors.It provides suggestions for heating detection of different GIS equipment and different use conditions.?5?At the dynamic and static contacts of GIS bus conductor and disconnector,it is suggested to combine surface acoustic wave?SAW?temperature measurement with infrared radiation temperature measurement,and to study the selection and installation of heating detection device.Through theoretical research,simulation and engineering application requirement analysis of detection methods,it is concluded that:?1?The heating of busbar and disconnector in GIS equipment is serious.The main heating phenomena are ablation,ablation and burnout.The main heating reasons are single-phase short-circuit heating,contact resistance increasing heating,cracks in insulation equipment,foreign bodies and so on.?2?Through the analysis of heating mechanism,we can get the following conclusions:?1?The heat source of GIS bus comes from Joule loss of conductor,eddy current loss of shell and solar radiation;heat transfer mainly refers to solid heat transfer and radiation of bus conductor and shell itself,heat transfer and radiation between conductor,shell,SF₆ gas and ambient temperature;and?2?The heat source of GIS disconnector is similar to bus,but needs to be added.Resistance loss caused by contact resistance;heat transfer process is similar to that of busbar.Heat transfer between shield cover and SF₆ gas needs to be added.?3?Temperature rise simulation under power frequency and short circuit conditions can be obtained as follows:?1?the temperature of horizontal GIS bus bar and disconnector is high and low,the temperature distribution of cross section and gas flow velocity are basically symmetrical;?2?when the ambient temperature is 20 C,with the increase of current passage time,the temperature of bus conductor and shell increases rapidly at first,then slows down,and finally tends to be stable,and the temperature of conductor is slightly larger.The temperature of the isolator contacts and shielding cover increases obviously,and the shell changes slightly,nonlinearly and positively with the temperature of the conductor contacts.?3?The heat of GIS disconnector is more serious.When the bus bar and disconnector are in thermal equilibrium state,the upper layer temperature difference is smaller,the gas convection is obvious,the lower layer temperature gradient is distinct and the convection is very small.The highest temperature point is near the top of a certain phase conductor,dynamic and static contacts,and the lowest point appears at the bottom of the shell.The highest temperature of the equipment can be used as the detection part.?4?For the GIS equipment that will be put into operation and after power failure,it is suggested to use the loop resistance method to judge whether there is a heating part caused by bad contact;for the heating detection of the GIS equipment that has been put into operation,it is suggested to use infrared thermal imaging method to measure the surface temperature of the shell and to deduce the temperature of the internal contact and the location of the overheated spot;for the newly designed GIS disconnector,it is possible to use the infrared thermal imaging method to deduce the temperature of the inner contact and the location of the overheated Surface acoustic wave?SAW?,infrared radiation?IRR?or distributed fiber Bragg grating?DFBG?are used to monitor temperature in the design process.?5?For the heat detection of bus conductor in GIS,it is suggested that the infrared thermal imaging method be used to measure the temperature as a whole,and the combination of surface acoustic wave?SAW?temperature measurement and infrared radiation temperature measurement should be adopted at bus node,isolation switch dynamic and static contacts.The heat detection of GIS contacts should be based on the range of temperature rise and simulation results to select and arrange sensors.According to the above contents,the innovations of this paper are as follows:?1?According to the heating fault characteristics of GIS equipment,the temperature rise of GIS equipment under power frequency and short circuit conditions is simulated.?2?To analyze the application requirements of common heating detection methods in GIS temperature measurement.