Surface discharge of bulk materials investigated from change of charge trap characteristics of polyimide single molecular chain

Surface discharge is one of the reasons for insulation failure. Polyimide (PI) used in gas-solid high-frequency electric power equipment. Therefore, based on density functional theory, effects single molecular chain structure, energy level, states, electrostatic potential, excited state and other micro parameters under external field trap formation surface both PI polar- group- OH<sup>– </sup>affected are discussed from atomic level. The results show that structure crimped dipole moment increases field, which easy to accumulate charges form space charge center, especially after introduction polar group OH<sup>–</sup>. In molecules, hole traps formed benzene ring region, electron imide region. number levels large, depth gradually deepens with increase field. After OH<sup>–</sup>, excitation molecules decreases, makes electrons inside easily. spatial separation holes decreases conducive recombination emit photons.