If the transformer oil isn`t degassed before injection transformer, when the transformer put into operation, since the internal temperature and pressure changes of the transformer body, the gas dissolved in the transformer oil is gradually released, or the surface of the solid transformer oil bubbles will appear, because of the dielectric constant of the bubbles is much larger than the transformer oil, which breakdown voltage below the breakdown voltage of the insulating oil, the bubbles easier partial discharge occurs in the operation, frequent discharge will continue to damage the transformer insulation. If the dissolved gases in the transformer oil reaches a certain level, it will release large volumes of gas, these gases will not only make the operation of the Buchholz relay air bridge is formed, and may be provided along the direction of the electric field, causing the transformer internal breakdown, it is a serious threat for operation of the transformer. The gas contained in the transformer oil, and acetylene is a special gas, acetylene generate at 700 degrees. 2 or more under high energy discharge to generate, so become an important basis for determining transformer internal spark discharge or arcing fault, since the insulating the oil in the refining process produces acetylene gas, if don`t degass before inject the oil to transformer, it will seriously affect the discharge of transformer internal fault judgment. So we suggest use the vacuum transformer oil filtration machine to do degass process.