Tianhui Li

Investigation on the placement effect of UHF sensor and propagation characteristics of PD-induced electromagnetic wave in GIS based on FDTD method

Using ultra-high-frequency (UHF) method in practical partial discharge (PD) detection can be affected by the positioning and placement of the UHF sensor. This in turn can affect the PD diagnosis. To ensure optimal performance of the sensor and understand the propagation process of electromagnetic (EM) wave, there is a need to fully analyze how the sensors placement affects the output signal and the attenuation of EM wave in various positions and directions. As the previous researches are mainly concentrating on the radial component of the UHF signal, the propagation of the signal components in axial and radial directions and that perpendicular to the radial direction of the GIS tank are investigated in detail in this paper. Firstly, the attenuation of UHF signals at different radial positions of a GIS model is analyzed using the finite difference time domain (FDTD) method. Then, secondly, the coupled signals in the three directions are calculated respectively. By comparing the signal received for different directions and circumferential angles, the peak to peak value (Vpp) and cumulative energy of the coupled voltage in each case are considered both in the time and frequency domain. As well, the attenuation characteristics and rules are summarized, based on which a new method for circumferential and axial location is proposed. The investigation on the propagation and the detection mechanism of EM wave in GIS provides a significant understanding of the application of UHF sensor and actual PD detection.

The Influence of L-Shaped Structure on Partial Discharge Radiated Electromagnetic Wave Propagation in GIS

To clarify the propagation process and improve the utilization of ultrahigh frequency (UHF) technique in partial discharge diagnosis, the propagation characteristics of electromagnetic wave in different directions in an L-shaped gas insulated switchgear tank are profoundly investigated in this paper. According to the property of electric field distribution and attenuation curves of the UHF signal, the influence of L-shaped structure is analyzed.

Experimental research on partial discharge radiated UHF signal attenuation characteristics in GIS

For detecting partial discharge (PD) phenomenon in gas insulated switchgear (GIS), ultra-high-frequency (UHF) method, which detects electromagnetic wave (EM wave) in UHF band with good immunity to noise, has been widely employed to avoid insulation accidents. In order to deeply understand the propagation process of EM wave and improve the utilization of the UHF method, it is necessary to investigate the attenuation characteristics of UHF signal from broadband PD sensor. In this research, by using the self-designed planar equiangular spiral antenna, the output UHF signal is detected and analyzed experimentally in a 252 kV GIS with L-shaped structure (LS) and disconnecting switch (DS) tank. When DS is closed and is open, the output signal is measured under two applied voltage levels individually in the test. And the results are mainly investigated in detail by time, statistics and frequency analysis. The propagation rules of the peak to peak value (Vpp) and transmission rate of the UHF signal are summarized. This research provides some referential significance towards the rational use of UHF method and better implementation of PD detection.

Experimental investigation on UHF partial discharge sensor in GIS

Detecting the partial discharge (PD) phenomenon in gas insulated switchgear (GIS) by using ultra-high-frequency (UHF) method is an effective diagnosis method to avoid insulation accidents. The most crucial part of UHF detecting system is ultra high frequency sensor. So a partial discharge (PD) sensor based on two-arm equiangular spiral antenna is designed and optimized in previous work. To examine the performance of the designed sensor when receiving the actual PD signal, several experiment test is performed in this research. The experimental setup including a PD model is built at the beginning. Then, the comparative test of the sensors with different impedance transformer (IT) is made, which indicates that the one with optimized IT has lower amplitude signal. And the tests by using different PD defects are also executed. It shows that the signal of the sensors can reflect the existence of PD as well as the feature of each kind of defect. In order to examine the change of the received signal when the distance varies, the experimental test are performed in the condition of the distance increasing in two directions respectively, which confirm that the change of the sensor position does not have obvious influence to the received signal. This paper further verified that the designed UHF sensor can effectively receive the PD signal and has good receiving performance to be used in PD detection.

The optimal circumferential angle position of UHF sensor for partial discharge detection in GIS

Ultra-high-frequency (UHF) technique for detecting partial discharge (PD) phenomenon is a useful method to avoid insulation accidents in gas insulated switchgear (GIS). However, the circumferential angle position of UHF Sensor in GIS has a great effect on the PD detection, which has not been investigated sufficiently. To deeply investigate the propagation characteristics of UHF signal and improve the application of the UHF technique, the influence of circumferential angle position of UHF Sensor in GIS is studied by performing several experiment tests in this paper. Applying two-arm equiangular spiral antenna as PD sensor, which is designed and optimized previously, the experimental platform is built based on a actual 252 kV GIS tank. Then, a protrusion defect is set on three circumferential angle positions respectively to achieve different relative position of the sensor and the defect, and the UHF signal received by the sensor in each case are analyzed statistically. The results indicate that different relative position of the sensor and the defect does have obvious influence to the received signal. Because the transmission rate of the UHF signal is the highest when the circumferential angle between the sensor and defect is 0°, this position is considered to be the optimal circumferential angle position of UHF Sensor to detect PD in GIS. This paper gives some referential suggestion for the rational application of UHF method in PD detection.

The influence of T-shaped structure on partial discharge radiated electromagnetic wave propagation in GIS

When ultra-high-frequency (UHF) method is applied in partial discharge (PD) detection for GIS, the propagation and rules of electromagnetic (EM) wave need to be understood clearly for conducting diagnosis and assessment about the real insulation status. The preceding researches are mainly concerning about the radial component of electromagnetic (EM) wave, but the propagation of the components in axial and radial directions and that perpendicular to the radial direction of the GIS tank are rarely considered. So in this research, in order to clarify the propagation process and improve the utilization of UHF technique in PD diagnosis, the propagation characteristics of EM wave in different directions in a 252 kV GIS with T-shaped structure (TS) are profoundly investigated. The attenuation rules of the peak to peak value (Vpp) and cumulative energy are concluded. According to the property of electric field distribution and attenuation curves of the UHF signal, the influence of T-shaped structure is analyzed. This paper discusses the propagation mechanism of UHF signal in T-shaped tank, which provides a better understanding of the PD propagation process as well as some referential significance towards the utilization of UHF technique.

Study on propagation characteristics of partial discharge-induced UHF signal in GIS with L shaped structure

Detecting the partial discharge (PD) phenomenon in gas insulated switchgear (GIS) by using ultra-high-frequency (UHF) method is an effective diagnosis method to avoid insulation accidents. Practically, UHF sensor will receive various signal components due to different placements and installation locations, which can greatly influence the diagnostic analysis result. Thus, in order to deeply understand the propagation process of electromagnetic (EM) wave and develop the utilization of the UHF method, it is necessary to investigate the attenuation process of EM wave in each circumferential angle and direction. In this research, the propagation characteristics of UHF signals in the GIS model with L shaped structure is analyzed thoroughly by using finite difference time domain (FDTD) method. Comparing the results in straight GIS tank, the influence of L shaped structure to the attenuation of PD signals in different circumferential angles and directions is mainly analyzed. And the propagation rules of the peak to peak value (Vpp) and cumulative energy of the coupled voltage in each case are summarized. This paper elucidates the propagation mechanism of EM wave in L shaped tank and lays a foundation for the rational use of UHF sensor and better conduct of PD detection.