Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These c...Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These cells had already been in use for years for example to test the electromagnetic compatibility of electronic devices.The smaller the size of the cell,the higher its bandwidth-but the cell should be large enough to not disturb the electric field with the installed sensor under test.To overcome this problem,a calibration procedure using a gigahertz transverse electromagnetic (GTEM) test cell and a pulsed signal source were introduced in 1997.Although this procedure has many advantages and is easy to understand,measurements show several shortcomings of this calibration method.To overcome the disadvantages of the known systems,a calibration cell using a monopole cone antenna and a metallic ground plane were developed and tested.The UHF sensor was placed in a region with minimum distortion of the electric field due to its installation.Experience shows that the new method for calibrating UHF sensors is necessary in order to overcome the limits in the calibration of large sensors and to suppress the propagation of higher order modes and reflections.Due to its surprisingly simple structure,its low price and low overall measurement uncertainty,it is the preferred method for calibrating UHF sensors for GIS applications.展开更多
The measuring of VFT phase voltage in three-phase enclosed GIS is more complex and difficult than in single-phase ones. There are 3 capacitive sensors in the measuring system, the outputs of which are with a linear re...The measuring of VFT phase voltage in three-phase enclosed GIS is more complex and difficult than in single-phase ones. There are 3 capacitive sensors in the measuring system, the outputs of which are with a linear relation to the three phase voltages. This linear relation is presented with a factorial matrix. Because each capacitive sensor is coupled with the electric field of three phases (A, B, and C), the electric coupling coefficients are introduced. In order to determine the matrix of electric coupling coefficients, the numerical calculation method can be used. From the discussion on two types of three-phase enclosed GIS bus, i.e. standard arrangement and biased arrangement, the dominant electric coupling coefficients are named, which can be simply and approximately calculated by an analytic expression. Finally, as an example, the waveforms of VFT phase voltage generated on a three-phase enclosed GIS bus model are displayed. When a capacitive sensor is located at the ’shortest point’ of phase A (or B, or C), the VFT phase voltage V A (or V B, or V C) can almost be measured by that capacitive sensor alone.展开更多
One of the fundamental issues in gas insulated substations （GIS） which has destructive effects on GIS equipment is the very fast transient over-voltages （VFTOs）. This paper models a 400/230 kV substation in order ...One of the fundamental issues in gas insulated substations （GIS） which has destructive effects on GIS equipment is the very fast transient over-voltages （VFTOs）. This paper models a 400/230 kV substation in order to study the effects of VFTO extensively implemen- ted on EMTP-RV. In addition, the application of ferrite rings for suppressing VFTOs is assessed thoroughly. The main advantage of this paper is its new proposed algorithm according to the ferrite ring frequency dependent modeling that is validated with experimental results. This paper examines the effects of three compositions of the ferrite ring on VFTO suppression. Moreover, it estimates the dimension of the ferrite ring based on the SF6 gas insulation withstand and the maximum effect of ferrite rings on VFTO suppression constraint with the COMSOL multiphysics software. Furthermore, it gains VFTO attenuated percentages due to the installation of the ferrite ring in different GIS nodes. Finally, it analyzes the offered VFTO amendment technique in various GIS switching scenarios.展开更多
文摘Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These cells had already been in use for years for example to test the electromagnetic compatibility of electronic devices.The smaller the size of the cell,the higher its bandwidth-but the cell should be large enough to not disturb the electric field with the installed sensor under test.To overcome this problem,a calibration procedure using a gigahertz transverse electromagnetic (GTEM) test cell and a pulsed signal source were introduced in 1997.Although this procedure has many advantages and is easy to understand,measurements show several shortcomings of this calibration method.To overcome the disadvantages of the known systems,a calibration cell using a monopole cone antenna and a metallic ground plane were developed and tested.The UHF sensor was placed in a region with minimum distortion of the electric field due to its installation.Experience shows that the new method for calibrating UHF sensors is necessary in order to overcome the limits in the calibration of large sensors and to suppress the propagation of higher order modes and reflections.Due to its surprisingly simple structure,its low price and low overall measurement uncertainty,it is the preferred method for calibrating UHF sensors for GIS applications.
文摘The measuring of VFT phase voltage in three-phase enclosed GIS is more complex and difficult than in single-phase ones. There are 3 capacitive sensors in the measuring system, the outputs of which are with a linear relation to the three phase voltages. This linear relation is presented with a factorial matrix. Because each capacitive sensor is coupled with the electric field of three phases (A, B, and C), the electric coupling coefficients are introduced. In order to determine the matrix of electric coupling coefficients, the numerical calculation method can be used. From the discussion on two types of three-phase enclosed GIS bus, i.e. standard arrangement and biased arrangement, the dominant electric coupling coefficients are named, which can be simply and approximately calculated by an analytic expression. Finally, as an example, the waveforms of VFT phase voltage generated on a three-phase enclosed GIS bus model are displayed. When a capacitive sensor is located at the ’shortest point’ of phase A (or B, or C), the VFT phase voltage V A (or V B, or V C) can almost be measured by that capacitive sensor alone.
文摘One of the fundamental issues in gas insulated substations （GIS） which has destructive effects on GIS equipment is the very fast transient over-voltages （VFTOs）. This paper models a 400/230 kV substation in order to study the effects of VFTO extensively implemen- ted on EMTP-RV. In addition, the application of ferrite rings for suppressing VFTOs is assessed thoroughly. The main advantage of this paper is its new proposed algorithm according to the ferrite ring frequency dependent modeling that is validated with experimental results. This paper examines the effects of three compositions of the ferrite ring on VFTO suppression. Moreover, it estimates the dimension of the ferrite ring based on the SF6 gas insulation withstand and the maximum effect of ferrite rings on VFTO suppression constraint with the COMSOL multiphysics software. Furthermore, it gains VFTO attenuated percentages due to the installation of the ferrite ring in different GIS nodes. Finally, it analyzes the offered VFTO amendment technique in various GIS switching scenarios.
