PURPOSE: To eliminate vetilation during an operation by a method wherein liquid nitrogen and liquid oxygen are separately introduced into respective two layers around an oil-filled cable with a weight ratio close to the composition ratio of the atmosphere to freeze the cable and, after produced nitrogen gas and oxygen gas are mixed, the mixed gas is discharged out.
CONSTITUTION: A buffer material 2 is wound around an oil-filled cable 1 and a cylindrical container 7 into which liquid nitrogen 4 is introduced is provided outside the buffer material 2 and, further, a cylindrical container 6 into which liquid oxygen 3 is introduced is provided outside the cylindrical container 7. The liquid nitrogen 4 and the liquid oxygen 3 are introduced into the cylindrical containers 6 and 7 with a weight ratio close to the composition ratio of the atmosphere, i.e., 0.78 of nitrogen and 0.21 of oxygen to freeze the oil-filled cable. Gases produced by freezing are transferred into a mixing chamber 8 and, after it is confirmed that the composition ratio of the mixed gas is equal to the composition ratio of the atmosphere, the mixed gas is discharged out through a discharge outlet 9.
KAZAMA YOJI
TAKAHASHI KAZUO
HITACHI CABLE