Study On The Key Problem In UHF Sensor Performance Calibration Based On GTEM Cell

UHF sensor is the key equipment of partial discharge detection system in GIS, and its performance has a great impact on the diagnosis accuracy. Because the performances of UHF sensor produced by different manufacturers are of great variety, unified and effective performance calibration methods are still illegibility. It is the most widely used method that temporal reference calibration based on GTEM cell. However, some problems, such as deficiency of optimal design on test window and its size, great difference between the actual response and the theoretical one of reference antenna, the lack of relevant regulations on pulse signal source parameter and the verification of consistency between frequency-domain reference calibration results and this method, need to solve. Therefore, researches as follow are launched.FDTD simulation model of GTEM cell has been built to analysis the field uniformity around test window affected by its position and size. That simulation model has been verified by experiment. It shows that the less distance of windows and feeding ports and the larger size of test window, the more significant effect of parameters and field uniformity; when diameter of test window is 300mm and the distance of windows and feeding ports is 3m, uniformity of electric field and characteristic parameters have metered the test requirements fairly.With the consideration of the monopole antenna reception principle and coaxial feed impedance matching, a optimization design method on installation of reference antenna flange has been put forward, which bridged the gap between the theoretical value and the actual response of the reference antenna. The deviation between them is only 4 percent.The effect of the raise time of pulse in time domain broadband reference calibration method on accuracy of UHF sensor equivalent height calibration has been experimentally studied in the first time. Furthermore, relevant parameter index of pulse source needed for calibration of UHF sensor has been given.Based on GTEM cell, experimental platform of UHF sensor frequency domain calibration has been built and corresponding measurement and control software has been developed. Equivalent heights of 50mm monopole antenna and DMS sensor have been measured and compared with temporal reference calibration. The consistency of the two calibrations has been verified on the same calibration platform, for the first time.