Power transformer for converter stations in high voltage direct current installations

摘要

Power transformer for converter stations in high voltage direct current installations with insulated electrodes (101 whereby the term "electrodes" refers to metallic surfaces and bodies in the transformer. According to the invention the electrodes are covered by an insulating lining (12) consisting of at least three layers of a tape or sheet formed wrapping material (13) having a fibrous and porous structure. The individual layers have through-going pores or openings with an opening area of 0.2-10 mm2 and with a total pore surface of 20-80% of the total surface of the wrapping material. The effect of this insulation is that ions - generated by the high d.c. electric field strength outside the electrodes - on their approaching the electrodes do not sense the porous tape insulation as any noticeable obstacle, while at the same time the insulating layer is sufficiently dense to increase the dielectric breakdown voltage so as to withstand in the case of electric surge voltages.