Uhf Wideband Partial Discharge Detection Sensor And The Signal Processing Circuit

Partial Discharge(PD) is one of the important reasons causing power transformer faults. This paper makes a deep research on the generating mechanism of PD and ultra high frequency detecting technology for partial discharge based on the current power transformer partial discharge detection technology.In this paper, an equivalent circuit of partial discharge model about electrical insulating medium will be established, based on the research of the generating mechanism of PD. In view of the breakdown mechanism of power dielectric, it introduces the characteristics of composite medium's structure, explains the generating mechanism of PD in power transformer, and summarizes the defects causing power transformer's PD. The equivalent circuit of PD is established on the basis of the fact that electromagnetic radiation will exist when PD happens, which is explained by electro-magnetic field theory, then the paper contrasts the equivalent circuit and PD signals measured by researchers at home and abroad in the laboratory in order to verify the validity of the equivalent circuit model.With in-depth study on antenna principle and HFSS simulation software, a small size plane deformation helical antenna for receiving PD signals is designed. Moreover, a plane equiangular spiral antenna and a plane Archimedes spiral antenna are designed, whose operating frequency is 500-1500MHz. By simulating them and comparing their simulation results, the impedance of the latter proves superior to the former on condition that they have the same diameter. Based on this simulation, we design a loading equiangular planar spiral antenna and a deformation planar spiral antenna by integrating the indexes, such as the antenna's efficiency, gain, size. The comparison between two antennas indicates that the other indexes, except for that of the gain, satisfy the design requirements, and the external diameter of two antennas could be reduced by 16.7%. In addition, the deformation planar spiral antenna is superior to the loading equiangular one in the aspect of input impedance index, and its gain is 5.37dB, with half power angle more than 60°and standing wave ratio less than 0.75 under the 175 ohm feed. What's more, an index gradual type micro-strip balancer is designed. The simulation of it shows that balancer standing wave ratio is less than 1.70 in pass band, its gain more than-0.3dB, and it can transfer energy effectively.An Ultra-High Frequency Broadband Low-Noise Amplifier that is used to amplify PD signal is designed. Its technical index, include gain, band,VSWR, noise figure and gain flatness is balanced by introducing negative feedback with frequency response and adopting two stage amplification. The results of simulating the amplifier with ADS software show that it is absolutely stable within the pass-band frequency ranging from 500 to 1500MHz, its maximum gain reaches to 32.345dB and minimum gain is 31.715 dB, which illustrates that the flatness of gain is preferable, moreover, noise figure is less than 1.42, and input/output VSWR less than 1.4.