Research keywords (27)：
vacuum
, surface discharge, creepage discharge
, spacer
, charging, electrification
, flashover
, surface charge
, insulation design
, gas mixtures
, gas insulation
, surface roughness
, charging mechanism
, cylindrical insulator, hollow type, solid type
, charging characteristic under ac voltage excitation
, conditioning phenomena
, charge measurement
, surface coating
, shape of insulator
, insulating spacer in vacuum
, out gas
, shielding ring
, surface discharge in vacuum
, insulation using gas mixtures
, recovery of SF6 from gas mixture
, ceramic coating
, vacuum circuit breaker
, control of charging
, nitrogen
