| High voltage switchgear is a important devices in power system,the internal contact is too fever caused by the large current and large contact resistance,etc.Overheating may affect the safety of the switchgear itself and even the entire operation of the power grid,causing massive power outage.Because of power equipment joint has mechanical wear or material oxidation,there is a widespread contact resistance between the contact-surface.With the increasing of use fixed number of year,contact resistance between the surfaces will gradually increase.In recent years,most of serious electrical failures are caused by overheating which is result from the large contact resistance of some components.Therefore,designing a reliable switchgear contact online temperature measurement/control system and studying the contact resistance measurement method based on the temperature curve are very necessary.Firstly,a temperature monitoring/controlling system of switchgear contacts based on infrared temperature measurement and Wireless sensor network(WSN)is raised,the characteristic and principle of infrared temperature measurement are summarized,selecting the infrared temperature sensor,the features and selection basis of ZigBee wireless communication are introduced,the data transmission protocol is designed,the hardware circuit of data acquisition terminal and gathering node are designed and implemented.Secondly,in view of the PC algorithm/software part,the overall structure of the PC software is designed.Pretreatment of temperature monitoring data,prediction algorithm of temperature changing trend and the utility of the switch cabinet over-temperature warning are importantly researched.Defects hierarchies of electric power equipment is researched,the implementation methods and steps of upper computer software based on LabVIEW are introduced in detail.Then,tests of hardware platform and PC software show that online thermal monitoring/warning scheme of switchgear contacts is feasible,data of equipment status can be transformed reliably and fastly,information of monitoring/warning system is visualized,promoting the realization of electric power equipment state overhaul.using For different cooling scheme,using APH(analytic hierarchy process)research a best cooling way of a closed switchgear,the best way is installing a finned radiator in the rear panel of switchgear.Finally,the theoretical physical model and the radial transient thermal circuit model of electric contact components are established through theoretical research,the thermal circuit response equation is concluded importantly.The contact resistance model considering temperature and current is derived from the theory analysis,a method of measuring contact resistance by using the curve of thermal time constant is raised.A lot of theoretical analysis/calculation and finite element analysis of ANSYS simulation results show that the method can accurately obtain the value of the contact resistance,which provides theoretical support for on-line monitoring of contact resistance and thermal defect analysis of electric power equipment. |
PDF Full Text Request