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To calibrate non-contact sensors with fast response and high scale factor, it is critical to develop step pulse generators capable of generating standard high voltage step pulses and accurately measuring the generated waveform. In this paper, two types of step pulse generators are designed with output voltages of 2 kV and 100 kV. The 2 kV step pulse generator can generate a step pulse with a rise time of ∼300 ps and an adjustable pulse width. A step pulse with a rise time less than 5 ns and a pulse width over 1 μs can be generated with the 100 kV step pulse generator. The uncertainty of 2 kV step pulse generator is then analyzed by simulations and experiments. Finally, a performance comparison with step pulse generators in previous studies is carried out. Bandwidth, linearity and repeatability of the sensors can be verified with the designed two step pulse generators. [ABSTRACT FROM AUTHOR]

Owing to the strong penetration ability of X-rays and the imaging visibility, X-ray inspection has been gradually applied to power grids. However, various problems occur in the promotion and application of X-ray inspection in ultra high voltage gas-insulated switchgear (UHV GIS) owing to its large size. These problems relate to parameter selection, photography, protection area, random defect recognition, and risk assessment based on the X-ray image. In this paper, an X-ray digital imaging system is set up for UHV GIS inspection. Parameter selection for UHV GIS is discussed, and we demonstrate that UHV GIS can be photographed under a source-to-detector distance (SDD) of 2.8 m, a tube voltage of 300 kV, and an exposure of >240 mA·s. A photographic method for UHV GIS, entailing adjustment of the position of the imaging plate with a fixed position of the X-ray generator, is proposed to reduce the difficulty in image stitching. The influence of the parameters on imaging quality is discussed, and we show that the brightness and contrast increase with increasing exposure or decreasing SDD. The interactions between parameters are qualitatively introduced. Moreover, the sensitivity of X-ray inspection in UHV GIS is studied under selected parameters, and the sensitivity of X-ray inspection to copper particles and aluminum particles in UHV GIS are shown to be <0.7 mm and <1.1 mm, respectively. Radiation protection for operators is also discussed. In addition, a pseudo-color scheme for identifying random tiny defects is proposed to reduce human error. Finally, the risk level of defects with X-ray inspection is defined by size feature. [ABSTRACT FROM AUTHOR]

SF6 insulated current transformers (CTs) are widely used in high-voltage power systems due to their favorable insulating properties. Field experience shows that the high moisture content in an SF6-insulated CT is an important factor responsible for its insulation faults. Furthermore, the moisture content in an SF6-insulated system is generally dependent on the ambient temperature. Thus, in this paper, the temperature distribution and moisture content of an SF6-insulated CT are studied by considering current flowing through it and a sharp change in the ambient temperature. It is found that the temperature distribution of an SF6-insulated CT in operation is extremely uneven, and the measured moisture content becomes higher than the initial moisture content. The relative humidity in the lower part of the CT might reach a dangerous level when the ambient temperature changes rapidly. The mechanism of moisture condensation is proposed to explain the experimental results. Besides, the possible preventive measures for insulation failure are also discussed. [ABSTRACT FROM AUTHOR]