A UHF Sensor For On-line Partial Discharge Detection Of Power Equipment Based On Antipodal Vivaldi Antenna

Ultra high frequency(UHF)partial discharge detection method is widely used for partial discharge detection due to its high sensitivity and strong anti-interference ability,which can make effective early warning before power equipment failure.As a key component of the partial discharge detection system,the UHF sensor directly affects the safety detection of the power system.However,the existing UHF sensors are limited by their own characteristics,size and other factors,and cannot efficiently detect the electromagnetic waves generated by partial discharge.In order to solve the above problems,a new UHF sensor is designed based on the Vivaldi antenna,combining microwave and antenna theory,and focusing on the key issues of miniaturization,wide band and high gain.The main conclusions are as follows:1.Through the innovation of linear gradient structure in the part of the microstrip balun of antipodal Vivaldi antenna,it is found that the frequency range of the linear gradient balun is 0.76 GHz～1.26 GHz and 1.61 GHz～3.50 GHz compared with the ordinary microstrip barron,which is significantly larger than the frequency range of the latter 0.81 GHz～1.34 GHz,1.76 GHz～2.46 GHz and 2.94 GHz～3.50 GHz.This shows that the linear gradient microstrip barron has advantages over the ordinary microstrip balun in improving the impedance matching between the Vivaldi antenna and the transmission line.2.The following structure is loaded on the basis of the Vivaldi antenna fed by linear gradient microstrip balun:(1)By loading exponential gradient slots on both sides of the antipodal Vivaldi antenna and using the principle of one-quarter wavelength slot line opening to suppress the current generated by the surface waves at the edge of the antenna,it is found that this structure can effectively suppress the current at the edge of the antenna,so as to make as much signal energy radiate out along the slot line as possible.The experiment shows that the operating frequency band loaded with the structure is 0.77 GHz～3 GHz,and its bandwidth is 181% of that of the unloaded antenna;(2)By opening loading gradient exponential curve in radiation to chip,based on the radiation direction to slice to the radiation of electromagnetic wave has guiding effect for the experiment,the results showed that: Compared with Vivaldi antenna without this structure loaded,the gain of the antenna loaded with this structure can reach 5 d B～9.4 d B at 1.37 GHz～3 GHz,and its gain is significantly improved;(3)By loading the slot correction structure near the exponential radiation slot line,based on the theory of electromagnetic wave propagation in free space faster than that in metal,it was found that the slot correction structure can strengthen the surface electric field at the radiation slot line,so that the antenna end The radiation characteristics have been significantly improved,and a novel Vivaldi antenna with a working frequency band of 0.76 GHz to3.27 GHz and an antenna gain of 5 d B to 8.38 d B in the range of 1.4 GHz to 3 GHz has been developed.3.The resonant cavity of the new antenna is designed to perfect the development of UHF sensors,build a partial discharge detection platform,and use the developed UHF sensors to collect partial discharge signals to complete the time and frequency domain analysis.The results show that the developed UHF sensor performs well in the UHF band and is suitable for partial discharge detection.