The hermetically sealed transformer is the transformer of which inner tank is totally isolated from the outside atmosphere,its volume changes with shrinkage and expansion of the corrugated tank sides.Moisture and oxygen can not enter the tank from outside,thus slowing down the aging of the insulating material.It doesn't need core-lifting check before operation or maintenance after putting into operation,which greatly improves the reliability of transformer.It adopts PCCAD as design software,and meets IEC60076,GB1094 standard,and has passed the ISO9001 quality system certification.