Electrical Tree Characteristics of Epoxy Resin Under Lightning Impulse at Cryogenic Temperature

As the key cryogenic insulating material for high-temperature superconductivity equipment, epoxy resin works in the harsh environment of strong electric field and extremely cryogenic temperature, and its operational reliability faces severe challenges. In this article, aiming at bisphenol F epoxy resin for cryogenic insulation of super-conducting power equipment, researches on electrical trees in epoxy resin under lightning impulse voltage at room temperature and cryogenic temperature were carried out. The effects of temperature, impulse voltage amplitude, and polarity on the initiation characteristics, growth morphology, growth rate, and expansion coefficient of electrical trees are discussed. The results show that the electrical tree initiation under impulse voltage in a cryogenic environment also has a polarity effect. The voltage is higher than that under negative impulse voltage, the shape of electrical trees is a typical branch, the color is darker, the tree channel is wider, and the branches next to the channel are simpler. There are fewer branches, and many darker spherical or ellipsoidal cracks appear in the electrical branch channel.