油浸コンデンサ誘電体の直流•インパルスおよび直流•交流重畳電圧破壊特性

抄録

The breakdown test under DC-Impulse and DC-AC superposed voltage, of an oil impregnated capacitor dielectric is carried out to study the influence of a DC superposed voltage on the breakdown characteristics.
The insulation configuration of the dielectric includes three types-oil-impregnated paper, paperfilm (polypropylene), and all-film, each of which uses alkyl-naphthalene as the insulating oil in making a sample capacitor. From the DC-Impulse superposition test, it is found that the breakdown of each capacitor is determined by a certain algebraic sum of the DC and Impulse electric fields regardless of the polarity (forward or reverse polarity) and ratio of DC to Impulse.
From repetitive service-life test, it is found that the service life is inversely proportional to approx. the 13th power of the pulse electric field in the reverse-polarity pulse area of a paper capacitor and to approx. 55th power of it in the short-term area and short-time and sustained use areas of the foward-polarity pulse. For all-film and paper-film samples, it is found that the service life is inversely proportional to approx. the 55th power of the puls electric field in the sustained use area (several thousands of times) or both the foward and reverse polarities.
From the result of the DC-AC superposed voltage test, several facts can be obtained namely that the influence of the DC superposed voltage on the shortterm breakdown voltage is large for any dielectric configuration but, is small in the sustained use area.