Interference Analysis on SiteThe key to on-line partial discharge (PD) monitoring of power transformers is how to suppress interference effectively. This paper reports an interference qualitative and quantitative analysis on site using a Fast Fourier Transform (FFT) technique. Various periodic interferences have been found, which emanated froin the carrier coininunication and thyristor switching mainly. This paper will focus attention on how to use software to suppress these interferences.A multi-bandpass digital filter based on FFT has been developed to suppress continuous periodic interference, It is better than the other digital filters. Authors also developed a new pulse recognition method to suppress the periodic pulse interference effectively.
Electric field distortion caused by space charge accumulation is one of the challenges in the development of insulating liquid immersed converter transformers and battery energy storage. This paper studies the impact of temperature and moisture content on field distortion in synthetic ester through an improved computational model incorporating the time-development permittivity of insulating liquid, and the test results indicated highly accurate simulation results of electric field distribution can be produced compared with the previous model. Charge mobility and charge density in synthetic ester were extracted from frequency dielectric spectroscopy test results, which were then used to calculate field distortion by the developed computational model. Simulation results indicated that the field distortion in synthetic ester decreases with temperature due to the enhanced permittivity caused by space charge accumulation, while it increases with moisture content due to the increased charge density from the dissociation of water.
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