THE RESEARCH ON BREAKDOWN IN AC CAPACITOR FOR HVDC TRANSMISSION

摘要

Based on the operation of the AC capacitors made in P.R.CHINA for high voltage direct current (HVDC) transmission, this paper analyses the major failure phenomena, i.e. breakdown of domestic capacitors. Combining with the dielectric aging theory, both the aging mechanism of capacitor insulation, it is analyzed that the free radicals affect on aging of the liquid and solid dielectric and the heat and impurities are harm to the dielectric. It is proposed that the free radicals are the root inducing of the insulation aging in the capacitor. To restrain or prevent the radicals the harm to the molecules of the liquid dielectric is the key to solve the insulation aging in the capacitor. According to the analysis the reason of dielectric aging, several simply methods, by measuring of the insulation resistance or the loss between terminals and container or the capacitance between terminals in different ways, are proposed to determine whether the interior insulation of a capacitor has aged. By the analysis of the loss between terminals and container, it is found that the insulation aging of domestic all film capacitors have appeared in the international all film process. According to the research, it is proposed that methods of the cleanness control in production process, the choice of high aromatic insulation oil and to add the additives into the oil are helpful to solve or eliminate the insulation aging inside the capacitors and enhance the reliability of the HVDC capacitor operation. The technology of additive is where the shoe pinches.